Piezoelectric ceramic composition and method of production of same, piezoelectric element, and dielectric element

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a piezoelectric ceramic composition of a composition not containing lead and a method of production of the same and to a piezoelectric element and dielectric element using the piezoelectric ceramic composition as materials.

2. Description of the Related Art

In the past, as a piezoelectric ceramic composition, a PZT (PbTiO₃—PbZrO₃) component-based ceramic containing lead has been used. This is because the above PZT exhibits large piezoelectric properties and has a high mechanical quality factor superior in long-term stability and enables the easy fabrication of materials of various properties required for applications such as sensors, actuators, and filters.

Further, PZT has a high relative dielectric constant, so can also be used as a capacitor etc.

While a piezoelectric ceramic composition comprised of PZT has superior properties, it includes lead among its component elements, so harmful lead leaches out from the industrial waste of products containing the PZT and therefore environmental pollution is liable to be caused. The rising awareness of such environmental issues in recent years has made difficult the production of products which might become causes of environmental pollution such as with PZT. Therefore, development of a piezoelectric ceramic composition of a composition not containing lead is being sought. A piezoelectric ceramic composition of the general formula (K_1-xNa_x)NbO₃(where, 0<x<1) has become the focus of attention. (See Journal of the American Ceramic Society, U.S., 1962, vol. 45, no. 5, p. 209.)

(A) Problem to be Solved I

A piezoelectric ceramic composition of the general formula (K_1-xNa_x)NbO₃(where, 0<x<1) is difficult to fire, so hot press sintering is necessary. Therefore, there was the problem that the production costs became high.

Further, there was the problem that the piezoelectric ceramic composition of the above general formula suffered from low properties such as the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, and Curie temperature Tc. Therefore, application was difficult to piezoelectric elements requiring high piezoelectric d₃₁constants and electromechanical coupling coefficients Kp such as piezoelectric actuators, piezoelectric filters, piezoelectric vibrators, piezoelectric transformers, piezoelectric ultrasonic motors, piezoelectric gyrosensors, knock sensors, yaw rate sensors, air bag sensors, back sonar, corner sonar, piezoelectric buzzers, piezoelectric speakers, and piezoelectric ignitors. Further, since the Curie temperature Tc is low, there was the problem that the piezoelectric properties deteriorated under a high temperature environment.

The invention was made in view of the above problem and has as its object to provide a piezoelectric ceramic composition not containing lead, able to be sintered at ordinary pressure, and superior to the past in at least one of the properties unique to piezoelectric ceramic compositions such as the piezoelectric d₃₁constant and a method of production of the same and a piezoelectric element and dielectric element utilizing that piezoelectric ceramic composition.

(B) Problem to be Solved II

A piezoelectric ceramic composition of the above general formula (K_1-xNa_x)NbO₃(where, 0<x<1) suffers from the problem of low piezoelectric properties such as the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, and mechanical quality factor Qm. Therefore, application was difficult to a piezoelectric elements requiring a high piezoelectric d₃₁constant such as piezoelectric actuators, piezoelectric filters, piezoelectric vibrators, piezoelectric transformers, piezoelectric ultrasonic motors, piezoelectric gyrosensors, knock sensors, yaw rate sensors, air bag sensors, back sonar, corner sonar, piezoelectric buzzers, piezoelectric speakers, and piezoelectric ignitors.

Further, since the piezoelectric ceramic composition of the above general formula has low dielectric properties such as the relative dielectric constant ∈_33τ/∈₀and dielectric loss tan δ, there was the problem that application was difficult to a dielectric element such as a capacitor.

The present invention was made in view of the above problem in the prior art and has as its object to provide a piezoelectric ceramic composition not containing lead, having high piezoelectric properties and dielectric properties, and superior in at least one of the piezoelectric d₃₁constant, relative dielectric constant, dielectric loss, and Curie temperature Tc and a method of production of the same and a piezoelectric element and dielectric element utilizing that piezoelectric ceramic composition.

A piezoelectric ceramic composition of the above general formula (K_1-xNa_x)NbO₃(where, 0<x<1) suffers from the problem of low piezoelectric properties such as the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, and mechanical quality factor Qm and low dielectric properties such as the relative dielectric constant ∈_33τ/∈₀and dielectric loss tan δ. Therefore, application was difficult to piezoelectric elements requiring a high piezoelectric d₃₁constant and electromechanical coupling coefficient Kp such as piezoelectric actuators, piezoelectric filters, piezoelectric vibrators, piezoelectric transformers, piezoelectric ultrasonic motors, piezoelectric gyrosensors, knock sensors, yaw rate sensors, air bag sensors, back sonar, corner sonar, piezoelectric buzzers, piezoelectric speakers, and piezoelectric ignitors and to dielectric elements such as capacitors.

To solve this problem, in addition to the piezoelectric ceramic composition of the above general formula (K_1-xNa_x)NbO₃, various piezoelectric ceramic compositions of compositions not containing lead are being developed, but almost all of these cannot withstand practical use. Further, in general the piezoelectric d₃₁constant and mechanical quality factor Qm are contradictory in relationship, so it is particularly difficult to obtain a piezoelectric ceramic composition superior in both of the piezoelectric d₃₁constant and mechanical quality factor Qm.

The present invention was made in view of the above problem in the prior art and has as its object to provide a piezoelectric ceramic composition not containing lead, having high piezoelectric properties and dielectric properties, and superior in both of the piezoelectric d₃₁constant and mechanical quality factor Qm and a method of production of the same and a piezoelectric element and dielectric element utilizing that piezoelectric ceramic composition.

(D) Problem to be Solved IV

A piezoelectric ceramic composition of the above general formula (K_1-xNa_x)NbO₃(where, 0<x<1) suffers from the problem of being difficult to sinter. Therefore, the sintered piezoelectric ceramic composition features a low apparent density and tends to have a large number of pores in its surface and inside. Therefore, a conventional piezoelectric ceramic composition of the above general formula (K_1-xNa_x)NbO₃suffered from the problem of a susceptibility to a drop in its mechanical strength.

The present invention was made in view of the above problem in the prior art and has as its object to provide a piezoelectric ceramic composition not containing lead, having a high apparent density, and having a low porosity and open porosity and a method of production of the same and a piezoelectric element and dielectric element utilizing that piezoelectric ceramic composition.

(E) Problem to be Solved v

A piezoelectric ceramic composition of the above general formula (K_1-xNa_x)NbO₃(where, 0<x<1) suffers from the problem of low piezoelectric properties such as the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, and mechanical quality factor Qm. Therefore, application is difficult to piezoelectric elements requiring a high piezoelectric d₃₁constant and electromechanical coupling coefficient Kp such as piezoelectric actuators, piezoelectric filters, piezoelectric vibrators, piezoelectric transformers, piezoelectric ultrasonic motors, piezoelectric gyrosensors, knock sensors, yaw rate sensors, air bag sensors, back sonar, corner sonar, piezoelectric buzzers, piezoelectric speakers, and piezoelectric ignitors.

The present invention was made in view of the above problem in the prior art and has as its object to provide a piezoelectric ceramic composition not containing lead, having high piezoelectric properties and dielectric properties, and superior in at least one of the piezoelectric d₃₁constant, mechanical quality factor Qm, and relative dielectric constant and a method of production of the same and a piezoelectric element and dielectric element utilizing that piezoelectric ceramic composition.

SUMMARY OF THE INVENTION

(1) Means for Solving the Problem I

According to a first aspect of the present invention, there is provided a piezoelectric ceramic composition of a general formula {Li_z(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2.

As described above, the piezoelectric ceramic composition of the invention has a general formula of a type of perovskite structure ABO₃wherein elements of A site comprise either K and Na; or K, Na and Li; while elements of B site comprise Nb, Ta and Sb. In this formula, the ideal perovskite structure is attained when A:B is 1:1 (i.e. a stoichiometric ratio). However, for the purpose of the invention, the ratio A/B may vary because especially several % (e.g. 3%) of K, Na, Li and Sb may vaporize during sintering process, and all of the constituent elements may also vary to some extent (e.g. 3%) during mixing, milling or granulating. Thus, the stoichiometric composition may sometimes vary depending on the variation in manufacturing processes. Therefore, there are many cases where the formulation ratio of starting materials is intentionally adjusted in light of such a variation. It is true of conventional manufacturing processes for PZT, wherein the formulation ratio is commonly adjusted, taking into account that lead may vaporize during sintering and zirconia may be mingled as a contaminant from milling media of zirconia balls. For the purpose of the invention, the variation of the ratio A/B is allowed to the extent of ±5 mol % to obtain acceptable electric properties. Preferably, the variation of the ratio A/B is within ±3 mol % to obtain higher electric properties due to less lattice defect.

The piezoelectric ceramic composition of the first aspect of the/present invention, as shown by the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃, is a composition not containing lead.

Therefore, the piezoelectric ceramic composition is safe in that waste of the piezoelectric ceramic composition etc. does not leach harmful lead into the natural world.

Further, the piezoelectric ceramic composition has the x, y, z, and w in the above general formula in the above ranges. Therefore, the piezoelectric ceramic composition is superior in at least one of the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, relative dielectric constant ∈_33τ/∈₀, dielectric loss tan δ, and Curie temperature Tc.

Further, the piezoelectric ceramic composition has a range of z in the above general formula of 0<z≦0.4 and a range of w of 0<w≦0.2 and contains tantalum and antimony as essential ingredients. Therefore, the piezoelectric ceramic composition easily is densified at the time of sintering and can be sufficiently densified even by sintering under ordinary pressure. This is because the inclusion of tantalum and antimony as essential ingredients in the above ranges reduces the sintering temperature, the tantalum and antimony function as sintering aids, and sintering with little pores becomes possible. Therefore, there is no need for hot press sintering as in the past and the above piezoelectric ceramic composition can be fabricated simply and at a low cost. Further, the stability of the dielectric loss tan δ of the piezoelectric ceramic composition can be improved.

In this way, the piezoelectric ceramic composition is safe to the environment, can be sintered at ordinary pressure, and can be utilized as a material for a high performance piezoelectric element or dielectric element. Note that the piezoelectric ceramic composition in the first aspect of the present invention is not limited to a ceramic composition having piezoelectric properties and includes in concept also a dielectric ceramic composition having dielectric properties.

According to a second aspect of the present invention, there is provided a method of production of a piezoelectric ceramic composition comprising shaping and sintering a powder comprised of a piezoelectric ceramic composition of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2.

A shaped article obtained using a powder comprised of the above piezoelectric ceramic composition can be sintered at ordinary pressure. Therefore, it can be sintered simply and at a low cost. Further, the piezoelectric ceramic composition obtained after sintering does not contain lead and is superior in properties unique to piezoelectric ceramic compositions such as the piezoelectric d₃₁constant. Therefore, it can be utilized as a material for a high performance piezoelectric element or dielectric element.

According to a third aspect of the present invention, there is provided a method of production of a piezoelectric ceramic composition comprising mixing and sintering a compound containing lithium, a compound containing sodium, a compound containing potassium, a compound containing niobium, a compound containing tantalum, and a compound containing antimony so as to obtain a piezoelectric ceramic composition of the first aspect of the invention

In the third aspect of the present invention, as explained above, a compound containing lithium, a compound containing sodium, a compound containing potassium, a compound containing niobium, a compound containing tantalum, and a compound containing antimony are mixed and sintered. Due to this, the piezoelectric ceramic composition of the first aspect of the invention can be easily obtained.

Further, at the time of sintering, the piezoelectric ceramic composition can be sintered at ordinary pressure. Further, the piezoelectric ceramic composition obtained after sintering does not contain lead and is superior in properties unique to piezoelectric ceramic compositions such as the piezoelectric d₃₁constant. Therefore, it can be utilized as a material for a high performance piezoelectric element or dielectric element.

According to a fourth aspect of the present invention, there is provided a piezoelectric element having a piezoelectric body comprised of a piezoelectric ceramic composition of the first aspect of the invention.

The piezoelectric element of the fourth aspect of the invention has a piezoelectric body comprised of the piezoelectric ceramic composition of the first aspect of the invention. Therefore, the piezoelectric element does not contain lead and is safe to the environment.

Further, the piezoelectric element enables the direct utilization of the property of the piezoelectric ceramic composition of being superior in properties unique to piezoelectric ceramic compositions such as the piezoelectric d₃₁constant. Therefore, the piezoelectric element can be utilized as a piezoelectric sensor element having a high sensitivity, a piezoelectric vibrator and actuator having a high electromechanical energy conversion efficiency, or other superior piezoelectric element.

According to a fifth aspect of the invention, there is provided a dielectric element having a dielectric body comprised of a piezoelectric ceramic composition of the first aspect of the invention.

The dielectric element of the fifth aspect of the invention has a dielectric body comprised of the piezoelectric ceramic composition of the first aspect of the invention. Therefore, the dielectric element does not contain lead and is safe to the environment. Further, the dielectric element enables the direct utilization of the property of the piezoelectric ceramic composition of being superior in at least one of the properties of the relative dielectric constant, dielectric loss, and long-term stability of the dielectric loss etc. Therefore, the dielectric element can be utilized as a large electrostatic capacity capacitor or other superior dielectric element.

(2) Means for Solving the Problem II

According to a sixth aspect of the invention, there is provided a piezoelectric ceramic composition having a compound of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2 as a main ingredient, wherein the piezoelectric ceramic composition contains at least one metal element selected from palladium, silver, gold, ruthenium, rhodium, rhenium, osmium, iridium, and platinum as an added element, and a total of the contents of the added elements is 0.001 mol to 0.15 mol with respect to 1 mole of the compound of the above general formula.

The above additive may be added to the above piezoelectric ceramic composition having the general formula by substitutional addition or external addition.

As described above, the piezoelectric ceramic composition of the invention has a general formula of a type of perovskite structure ABO₃wherein elements of A Site comprise either K and Na; or K, Na and Li; while elements of B site comprise Nb, Ta and Sb. In this formula, the ideal perovskite structure is attained when A:B is 1:1 (i.e. a stoichiometric ratio). However, for the purpose of the invention, the ratio A/B may vary because especially several % (e.g. 3%) of K, Na, Li and Sb may vaporize during sintering process, and all of the constituent elements may also vary to some extent (e.g. 3%) during mixing, milling or granulating. Thus, the stoichiometric composition may sometimes vary depending on the variation in manufacturing processes. Therefore, there are many cases where the formulation ratio of starting materials is intentionally adjusted in light of such a variation. It is true of conventional manufacturing processes for PZT, wherein the formulation ratio is commonly adjusted, taking into account that lead may vaporize during sintering and zirconia may be mingled as a contaminant from milling media of zirconia balls. For the purpose of the invention, the variation of the ratio A/B is allowed to the extent of ±5 mol % to obtain acceptable electric properties. Preferably, the variation of the ratio A/B is within ±3 mol % to obtain higher electric properties due to less lattice defect.

Next, the action and effects of the present invention will be explained. The piezoelectric ceramic composition of the present invention is a composition not containing lead. Therefore, the piezoelectric ceramic composition is safe in that its waste etc. do not leach harmful lead into the natural world.

Further, the piezoelectric ceramic composition contains the compound of the above general formula and has the x, y, z, and w in the above general formula in the above ranges. Therefore, the piezoelectric ceramic composition is superior in the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, and other piezoelectric properties, the relative dielectric constant ∈_33τ/∈₀, dielectric loss tan δ, and other dielectric properties, and Curie temperature Tc. Note that a composition of the above general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃not containing the above added elements will be referred to below as the “basic composition”.

The piezoelectric ceramic composition contains, in addition to the compound of the basic composition of the above general formula, at least one type of metal element selected from palladium, silver, gold, ruthenium, rhodium, rhenium, osmium, iridium, and platinum as added elements in a total in the above range of content. Therefore, the piezoelectric ceramic composition of the present invention is further improved in at least one property among the piezoelectric d₃₁constant, piezoelectric g₃₁constant, electromechanical coupling coefficient Kp, relative dielectric constant δ_33τ/∈o, dielectric loss tan δ, and Curie temperature Tc and is more superior even compared with a piezoelectric ceramic composition of the above general formula not containing the added elements.

In this way, the piezoelectric ceramic composition of the present invention does not contain lead and therefore is safe to the environment and further has superior piezoelectric properties, so can be utilized as a high performance piezoelectric element.

Further, the piezoelectric ceramic composition is superior in the relative dielectric constant, dielectric loss, and other dielectric properties in addition to the above piezoelectric properties. Therefore, it can be utilized as a high performance dielectric element as well. That is, the piezoelectric ceramic composition of the sixth aspect of the invention is not limited to a piezoelectric ceramic composition having piezoelectric properties and includes in concept a dielectric ceramic composition having dielectric properties as well.

According to a seventh aspect of the invention, there is provided a method of production of a piezoelectric ceramic composition comprising mixing and sintering a compound of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2 and an additive including at least one metal element selected from palladium, silver, gold, ruthenium, rhodium, rhenium, osmium, iridium, and platinum.

The mixture obtained by mixing the compound of the above general formula and the above additive can be sintered under ordinary pressure. Therefore, it is possible to fire it simply and at a low cost. Further, the piezoelectric ceramic composition obtained after sintering does not contain lead and is superior in piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, and other piezoelectric properties and dielectric loss, relative dielectric constant, and other dielectric properties. Therefore, it can be used as a material for a high performance piezoelectric element or a dielectric element.

Further, the piezoelectric ceramic composition obtained after sintering has the above additive added to it, so has at least part of at least one type of the lithium, potassium, sodium, niobium, tantalum, and antimony of the compound of the above general formula substituted by at least one type of metal element selected from palladium, silver, gold, ruthenium, rhodium, rhenium, osmium, iridium, and platinum or has the above metal elements or oxides or perovskite structure compounds containing the same included in the grains or at the grain boundaries of the piezoelectric ceramic composition. Note that the “containing an additive” in this specification includes all of the above meanings.

The above additive may be added to the above piezoelectric ceramic composition having the general formula by substitutional addition or external addition.

According to an eighth aspect of the invention, there is provided a method of production of a piezoelectric ceramic composition comprising mixing a compound containing lithium, a compound containing sodium, a compound containing potassium, a compound containing niobium, a compound containing tantalum, and a compound containing antimony by a stoichiometric ratio giving, after sintering, a compound of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2 or a stoichiometric ratio considering substitution by a metal element contained in the following additive, mixing an additive containing at least one metal element selected from palladium, silver, gold, ruthenium, rhodium, rhenium, osmium, iridium, and platinum, and sintering the result.

In the eighth aspect of the invention, as explained above, a compound containing lithium, a compound containing sodium, a compound containing potassium, a compound containing niobium, a compound containing tantalum, a compound containing antimony, and an additive containing at least one metal element selected from palladium, silver, gold, ruthenium, rhodium, rhenium, osmium, iridium, and platinum are mixed and sintered in the above stoichiometric ratio. Due to this, it is possible to easily obtain the piezoelectric ceramic composition of the sixth aspect of the invention.

Further, the piezoelectric ceramic composition obtained after sintering has the above additive added to it, so in the same way as in the seventh aspect of the invention, has at least part of at least one type of the lithium, potassium, sodium, niobium, tantalum, and antimony of the compound of the above general formula substituted by at least one type of metal element selected from palladium, silver, gold, ruthenium, rhodium, rhenium, osmium, iridium, and platinum or has the above metal elements or oxides or perovskite Structure compounds containing the same included in the grains or at the grain boundaries of the piezoelectric ceramic composition.

At this time, when mixing a compound containing lithium, a compound containing sodium, a compound containing potassium, a compound containing niobium, a compound containing tantalum, a compound containing antimony, and the above additive by a stoichiometric ratio considering substitution by metal elements included in the additive, it is possible to positively substitute at least part of at least one type of the lithium, sodium, potassium, niobium, tantalum, and antimony in the compound of the general formula with the metal elements included in the additive.

The “mixing . . . considering substitution by metal elements included in the additive” can be realized, for example when substituting the lithium of the compound of the above general formula by a metal element of the additive, reducing the amount of the compound containing the lithium and adding and mixing in the above additive in exactly the reduced amount and, overall, by mixing by a stoichiometric ratio so as to give a compound of the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃after sintering. When substituting the potassium, sodium, niobium, tantalum, or antimony in the above general formula as well, it is possible to realize this by reducing the amount of the compound containing the same and adding an additive containing the metal element desired to be substituted by in exactly the reduced amount. For example, when adding silver for substitution, the result becomes {Li_x(K_1-yNa_y)_1-xAg_u}(Nb_1-z-wTa_zSb_w)O₃.

On the other hand, by mixing a compound containing lithium, a compound containing sodium, a compound containing potassium, a compound containing niobium, a compound containing tantalum, and a compound containing antimony by a stoichiometric ratio giving a compound of the above general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃after sintering and further mixing the above additive into this and sintering the result, it is possible to positively produce a piezoelectric ceramic composition containing the above metal elements or oxides or perovskite structure compounds containing the same.

Further, in the eighth aspect of the invention, the composition can be sintered at ordinary pressure. Further, the piezoelectric ceramic composition obtained after sintering does not contain lead and is superior in piezoelectric properties or dielectric properties. Therefore, it can be used as a material for a high performance piezoelectric element and dielectric element etc.

According to a ninth aspect of the invention, there is provided a piezoelectric element having a piezoelectric body comprised of a piezoelectric ceramic composition of the sixth aspect of the invention.

The piezoelectric element of the ninth aspect of the invention has a piezoelectric body comprised of the piezoelectric ceramic composition of the sixth aspect of the invention. Therefore, the piezoelectric element does not contain lead and is safe to the environment.

According to a 10th aspect of the invention, there is provided a piezoelectric element having a piezoelectric body comprised of a piezoelectric ceramic composition produced by the method of production of the seventh or eighth aspect of the invention.

The piezoelectric element of the 10th aspect of the invention has a piezoelectric body comprised of a piezoelectric ceramic composition obtained by the above method of production. Therefore, the piezoelectric element directly utilizes the superior properties of the piezoelectric ceramic composition and can be utilized as a piezoelectric sensor element having a high sensitivity, a piezoelectric vibrator and actuator having a high electromechanical energy conversion efficiency, etc.

According to an 11th aspect of the invention, there is provided a dielectric element having a dielectric body comprised of a piezoelectric ceramic composition of the sixth aspect of the invention.

The dielectric element of the 11th aspect of the invention has a dielectric body comprised of the piezoelectric ceramic composition of the sixth aspect of the invention. Therefore, the dielectric element does not contain lead and is safe to the environment. Further, the dielectric element enables the direct utilization of the property of the piezoelectric ceramic composition of being superior in the relative dielectric constant, dielectric loss, etc. Therefore, the dielectric element can be utilized as a capacitor with a large electrostatic capacity.

According to a 12th aspect of the invention, there is provided a dielectric element having a dielectric body comprised of a piezoelectric ceramic composition produced by the method of production of the seventh or eighth aspect of the invention.

The dielectric element of the 12th aspect of the invention has a dielectric body comprised of a piezoelectric ceramic composition obtained by the above method of production. Therefore, the dielectric element directly utilizes the superior properties of the piezoelectric ceramic composition and can be utilized as a capacitor with a large electrostatic capacity etc.

(3) Means for Solving the Problem III

According to a 13th aspect of the invention, there is provided a piezoelectric ceramic composition having a compound of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2 as a main ingredient, wherein the piezoelectric ceramic composition contains at least one metal element selected from nickel, iron, manganese, copper, and zinc as an added element, and a total of the contents of the added elements is 0.001 mol to 0.08 mol with respect to 1 mole of the compound of the above general formula.

The above additive may be added to the above piezoelectric ceramic composition having the general formula by substitutional addition or external addition.

Further, the piezoelectric ceramic composition contains the compound of the above general formula and has the x, y, z, and w in the above general formula in the above ranges. Therefore, the piezoelectric ceramic composition is superior in the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, and other piezoelectric properties, the relative dielectric constant 6 dielectric loss tan δ, and other dielectric properties, and Curie temperature Tc. Note that a composition of the above general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃not containing the above added elements will be referred to below as the “basic composition”.

The piezoelectric ceramic composition contains, in addition to the compound of the basic composition of the above general formula, at least one type of metal element selected from nickel, iron, manganese, copper, and zinc as added elements in a total in the above range of content. Therefore, the piezoelectric ceramic composition of the present invention can be maintained at a high piezoelectric d₃₁constant equal to that of a piezoelectric ceramic composition of the above general formula not containing the added elements while being improved in the mechanical quality factor Qm. That is, it is possible to realize a piezoelectric ceramic composition superior in both of the piezoelectric d₃₁constant and the mechanical quality factor Qm.

In this way, the piezoelectric ceramic composition does not contain lead and therefore is safe to the environment and further has superior piezoelectric properties, so can be utilized as a high performance piezoelectric element. In particular, since the piezoelectric ceramic composition has a high mechanical quality factor Qm as explained above, a piezoelectric element using this piezoelectric ceramic composition is suppressed in heat generation when driving it in an electric field and therefore is more superior.

Further, the piezoelectric ceramic composition is superior in the relative dielectric constant, dielectric loss, and other dielectric properties in addition to the above piezoelectric properties. Therefore, the piezoelectric ceramic composition of the present invention can be utilized as a high performance dielectric element as well. That is, the piezoelectric ceramic composition of the 13th aspect of the invention is not limited to a piezoelectric ceramic composition having piezoelectric properties and includes in concept a dielectric ceramic composition having dielectric properties as well.

According to a 14th aspect of the invention, there is provided a method of production of a piezoelectric ceramic composition comprising mixing and sintering a compound of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2 and an additive including at least one metal element selected from nickel, iron, manganese, copper, and zinc.

The above additive may be added to the above piezoelectric ceramic composition having the general formula by substitutional addition or external addition.

The mixture obtained by mixing the compound of the above general formula and the above additive can be sintered under ordinary pressure. Therefore, it is possible to fire it simply and at a low cost. Further, the piezoelectric ceramic composition obtained after sintering does not contain lead and is superior in piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, mechanical quality factor Qm, and other piezoelectric properties or dielectric loss, relative dielectric constant, and other dielectric properties. Therefore, it can be used as a material for a high performance piezoelectric element or dielectric element.

Further, the piezoelectric ceramic composition obtained after sintering has the above additive added to it, so has at least part of at least one type of the lithium, potassium, sodium, niobium, tantalum, and antimony of the compound of the above general formula substituted by at least one type of metal element selected from nickel, iron, manganese, copper, and zinc or has the above metal elements or oxides or perovskite structure compounds containing the same included in the grains or at the grain boundaries of the piezoelectric ceramic composition. Note that the “containing an additive” in this specification includes all of the above meanings.

According to a 15th aspect of the invention, there is provided a method of production of a piezoelectric ceramic composition comprising mixing a compound containing lithium, a compound containing sodium, a compound containing potassium, a compound containing niobium, a compound containing tantalum, and a compound containing antimony by a stoichiometric ratio giving, after sintering, a compound of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2 or a stoichiometric ratio considering substitution by a metal element contained in the following additive, mixing an additive containing at least one metal element selected from nickel, iron, manganese, copper, and zinc, and sintering the result.

The above additive may be added to the above piezoelectric ceramic composition having the general formula by substitutional addition or external addition.

In the 15th aspect of the invention, as explained above, a compound containing lithium, a compound containing sodium, a compound containing potassium, a compound containing niobium, a compound containing tantalum, a compound containing antimony, and an additive containing at least one metal element selected from nickel, iron, manganese, copper, and zinc are mixed and sintered in the above stoichiometric ratio. Due to this, it is possible to easily obtain the piezoelectric ceramic composition of the 13th aspect of the invention.

Further, the piezoelectric ceramic composition obtained after sintering has the above additive added to it, so in the same way as in the 14th aspect of the invention, has at least part of at least one type of the lithium, potassium, sodium, niobium, tantalum, and antimony of the compound of the above general formula substituted by at least one type of metal element selected from nickel, iron, manganese, copper, and zinc or has the above metal elements or oxides or perovskite structure compounds containing the same included in the grains or at the grain boundaries of the piezoelectric ceramic composition.

Further, in the 15th aspect of the invention, the composition can be sintered at ordinary pressure. Further, the piezoelectric ceramic composition obtained after sintering does not contain lead and is superior in piezoelectric properties or dielectric properties. Therefore, it can be used as a material for a high performance piezoelectric element and dielectric element etc.

According to a 16th aspect of the invention, there is provided a piezoelectric element having a piezoelectric body comprised of a piezoelectric ceramic composition of the 13th aspect of the invention.

The piezoelectric element of the 16th aspect of the invention has a piezoelectric body comprised of the piezoelectric ceramic composition of the 13th aspect of the invention. Therefore, the piezoelectric element does not contain lead and is safe to the environment.

Further, the piezoelectric element enables the direct utilization of the property of the piezoelectric ceramic composition of being superior in properties unique to piezoelectric ceramic compositions such as the piezoelectric d₃₁constant and mechanical quality factor Qm. Therefore, the piezoelectric element can be utilized as a piezoelectric sensor element having a high sensitivity, a piezoelectric vibrator and actuator having a high electromechanical energy conversion efficiency, etc.

According to a 17th aspect of the invention, there is provided a piezoelectric element having a piezoelectric body comprised of a piezoelectric ceramic composition produced by the method of production of the 14th or 15th aspect of the invention.

The piezoelectric element of the 17th aspect of the invention has a piezoelectric body comprised of a piezoelectric ceramic composition obtained by the above method of production. Therefore, the piezoelectric element directly utilizes the superior properties of the piezoelectric ceramic composition and can be utilized as a piezoelectric sensor element having a high sensitivity, a piezoelectric vibrator and actuator having a high electromechanical energy conversion efficiency, etc.

According to an 18th aspect of the invention, there is provided a dielectric element having a dielectric body comprised of a piezoelectric ceramic composition of the 13th aspect of the invention.

The dielectric element of the 18th aspect of the invention has a dielectric body comprised of the piezoelectric ceramic composition of the 13th aspect of the invention. Therefore, the dielectric element does not contain lead and is safe to the environment. Further, the dielectric element enables the direct utilization of the property of the piezoelectric ceramic composition of being superior in the relative dielectric constant, dielectric loss, etc. Therefore, the dielectric element can be utilized as a capacitor with a large electrostatic capacity.

According to a 19th aspect of the invention, there is provided a dielectric element having a dielectric body comprised of a piezoelectric ceramic composition produced by the method of production of the 14th or 15th aspect of the invention.

The dielectric element of the 19th aspect of the invention has a dielectric body comprised of a piezoelectric ceramic composition obtained by the above method of production. Therefore, the dielectric element directly utilizes the superior properties of the piezoelectric ceramic composition and can be utilized as a capacitor with a large electrostatic capacity etc.

(4) Means for Solving the Problem IV

According to a 20th aspect of the invention, there is provided a piezoelectric ceramic composition having a compound of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2 as a main ingredient, wherein the piezoelectric ceramic composition contains at least one metal element selected from silver, aluminum, gold, boron, barium, bismuth, calcium, cerium, cobalt, cesium, copper, dysprosium, erbium, europium, iron, gallium, gadolinium, germanium, hafnium, holmium, indium, iridium, lanthanum, lutetium, magnesium, manganese, neodymium, nickel, palladium, praseodymium, platinum, rubidium, rhenium, ruthenium, scandium, silicon, samarium, tin, strontium, terbium, titanium, thulium, vanadium, yttrium, ytterbium, zinc, and zirconium, a total of the contents of the added elements is 0.0005 mol to 0.15 mol with respect to 1 mole of the compound of the above general formula, and an open porosity is not more than 0.4 vol %.

As described above, the piezoelectric ceramic composition of the invention has a general formula of a type of perovskite structure ABO₃wherein elements of A site comprise either K and Na; or K, Na and Li; while elements of B site comprise Nib, Ta and Sb. In this formula, the ideal perovskite structure is attained when A:B is 1:1 (i.e. a stoichiometric ratio). However, for the purpose of the invention, the ratio A/B may vary because especially several % (e.g. 3%) of K, Na, Li and Sb may vaporize during sintering process, and all of the constituent elements may also vary to some extent (e.g. 3%) during mixing, milling or granulating. Thus, the stoichiometric composition may sometimes vary depending on the variation in manufacturing processes. Therefore, there are many cases where the formulation ratio of starting materials is intentionally adjusted in light of such a variation. It is true of conventional manufacturing processes for PZT, wherein the formulation ratio is commonly adjusted, taking into account that lead may vaporize during sintering and zirconia may be mingled as a contaminant from milling media of zirconia balls. For the purpose of the invention, the variation of the ratio A/B is allowed to the extent of ±5 mol % to obtain acceptable electric properties. Preferably, the variation of the ratio A/B is within ±3 mol % to obtain higher electric properties due to less lattice defect.

Further, the piezoelectric ceramic composition contains the compound of the above general formula and contains the above added elements in the above range. Therefore, when sintering the piezoelectric ceramic composition at the time of fabrication, the added elements act as sintering aids to promote densification and enable easy sintering. Therefore, a good quality piezoelectric ceramic composition having a high apparent density and small number of pores is formed. Note that the porosity is the amount of pores caused inside and at the back surface of the piezoelectric ceramic composition expressed by vol %, while the open porosity is the amount of depressions formed at the front surface of the piezoelectric ceramic composition expressed by volt,

Further, the piezoelectric ceramic composition of the present invention has a low open porosity of not more than 0.4 vol %. Therefore, the piezoelectric ceramic composition can be utilized as a piezoelectric element superior in mechanical strength, resistant to degradation, and high in reliability such as a piezoelectric actuator, a piezoelectric vibrator, a surface wave filter, a piezoelectric sensor element, an ultrasonic motor, and a piezoelectric transformer.

Further, the piezoelectric ceramic composition of the present invention contains a compound of the above general formula {Li_x(K_1-yNa_y)_1-x}Nb_1-z-wTa₂Sb_w)O₃as its main ingredient. Therefore, the piezoelectric ceramic composition utilizes the superior piezoelectric and dielectric properties of the compound of the above general formula such as the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, mechanical quality factor Qm, relative dielectric constant, dielectric loss, and Curie temperature and becomes superior in these properties. Therefore, the piezoelectric ceramic composition can be utilized for a high performance piezoelectric element and dielectric element.

Note that a composition of the above general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃not containing the above added elements will be referred to below as the “basic composition”.

According to a 21st aspect of the invention, there is provided a method of production of a piezoelectric ceramic composition comprising mixing and sintering a compound of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2 and an additive including at least one metal element selected from silver, aluminum, gold, boron, barium, bismuth, calcium, cerium, cobalt, cesium, copper, dysprosium, erbium, europium, iron, gallium, gadolinium, germanium, hafnium, holmium, indium, iridium, lanthanum, lutetium, magnesium, manganese, neodymium, nickel, palladium, praseodymium, platinum, rubidium, rhenium, ruthenium, scandium, silicon, samarium, tin, strontium, terbium, titanium, thulium, vanadium, yttrium, ytterbium, zinc, and zirconium.

The mixture obtained by mixing the compound of the above general formula and the above additive can be sintered under ordinary pressure. Therefore, it is possible to fire it simply and at a low cost.

In particular, the piezoelectric ceramic composition of the above general formula has an additive containing the above metal elements added to it. Therefore, the added elements act as sintering aids and the piezoelectric ceramic composition becomes easier to sinter at the time of sintering. As a result, it is possible to improve the apparent density of the piezoelectric ceramic composition after sintering and possible to make formation of large pores at the front surface and inside more difficult and reduce the porosity and open porosity. Therefore, it is possible to improve the mechanical strength of the piezoelectric ceramic composition after sintering.

The piezoelectric ceramic composition obtained after sintering has the above additive added to it, so has at least part of at least one type of the lithium, potassium, sodium, niobium, tantalum, and antimony of the compound of the above general formula substituted by at least one type of metal element selected from silver, aluminum, gold, boron, barium, bismuth, calcium, cerium, cobalt, cesium, copper, dysprosium, erbium, europium, iron, gallium, gadolinium, germanium, hafnium, holmium, indium, iridium, lanthanum, lutetium, magnesium, manganese, neodymium, nickel, palladium, praseodymium, platinum, rubidium, rhenium, ruthenium, scandium, silicon, samarium, tin, strontium, terbium, titanium, thulium, vanadium, yttrium, ytterbium, zinc, and zirconium or has the above metal elements or oxides or perovskite structure compounds containing the same included in the grains or at the grain boundaries of the piezoelectric ceramic composition. Note that the “containing an additive” in this specification includes all of the above meanings.

Further, the piezoelectric ceramic composition obtained after sintering does not contain lead and is superior in piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, mechanical quality factor Qm, relative dielectric constant, dielectric loss, curie temperature, and other piezoelectric and dielectric properties. Therefore, it can be used as a material for a high performance piezoelectric element or dielectric element.

According to a 22nd aspect of the invention, there is provided a method of production of a piezoelectric ceramic composition comprising mixing a compound containing lithium, a compound containing sodium, a compound containing potassium, a compound containing niobium, a compound containing tantalum, and a compound containing antimony by a stoichiometric ratio giving, after sintering, a compound of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2 or a stoichiometric ratio considering substitution by a metal element contained in the following additive, mixing an additive containing at least one metal element selected from silver, aluminum, gold, boron, barium, bismuth, calcium, cerium, cobalt, cesium, copper, dysprosium, erbium, europium, iron, gallium, gadolinium, germanium, hafnium, holmium, indium, iridium, lanthanum, lutetium, magnesium, manganese, neodymium, nickel, palladium, praseodymium, platinum, rubidium, rhenium, ruthenium, scandium, silicon, samarium, tin, strontium, terbium, titanium, thulium, vanadium, yttrium, ytterbium, zinc, and zirconium, and sintering the result.

In the 22nd aspect of the invention, as explained above, a compound containing lithium, a compound containing sodium, a compound containing potassium, a compound containing niobium, a compound containing tantalum, a compound containing antimony, and an additive containing at least one metal element selected from silver, aluminum, gold, boron, barium, bismuth, calcium, cerium, cobalt, cesium, copper, dysprosium, erbium, europium, iron, gallium, gadolinium, germanium, hafnium, holmium, indium, iridium, lanthanum, lutetium, magnesium, manganese, neodymium, nickel, palladium, praseodymium, platinum, rubidium, rhenium, ruthenium, scandium, silicon, samarium, tin, strontium, terbium, titanium, thulium, vanadium, yttrium, ytterbium, zinc, and zirconium are mixed and sintered in the above stoichiometric ratio. Due to this, it is possible to easily obtain the piezoelectric ceramic composition of the 20th aspect of the invention.

Further, the piezoelectric ceramic composition obtained after sintering has the above additive added to it, so in the same way as in the 21st aspect of the invention, has at least part of at least one type of the lithium, potassium, sodium, niobium, tantalum, and antimony of the compound of the above general formula substituted by at least one type of metal element selected from silver, aluminum, gold, boron, barium, bismuth, calcium, cerium, cobalt, cesium, copper, dysprosium, erbium, europium, iron, gallium, gadolinium, germanium, hafnium, holmium, indium, iridium, lanthanum, lutetium, magnesium, manganese, neodymium, nickel, palladium, praseodymium, platinum, rubidium, rhenium, ruthenium, scandium, silicon, samarium, tin, strontium, terbium, titanium, thulium, vanadium, yttrium, ytterbium, zinc, and zirconium or has the above metal elements or oxides or perovskite structure compounds containing the same included in the grains or at the grain boundaries of the piezoelectric ceramic composition.

Further, in the 22nd aspect of the invention, the composition can be sintered at ordinary pressure. Therefore, the piezoelectric ceramic composition can be produced simply and at a low cost. Further, the piezoelectric ceramic composition obtained after sintering does not contain lead, is high in apparent density, has a small porosity and open porosity, and is superior in piezoelectric properties or dielectric properties. Therefore, it is superior in mechanical strength and can be used as a material for a high performance piezoelectric element and dielectric element etc.

According to a 23rd aspect of the invention, there is provided a piezoelectric element having a piezoelectric body comprised of a piezoelectric ceramic composition of the 20th aspect of the invention.

The piezoelectric element of the 23rd aspect of the invention has a piezoelectric body comprised of the piezoelectric ceramic composition of the 20th aspect of the invention. Therefore, the piezoelectric element does not contain lead and is safe to the environment.

Further, the piezoelectric element utilizes the property of the piezoelectric ceramic composition of being high in apparent density and low in porosity and open porosity and becomes superior in mechanical strength.

Further, the piezoelectric element enables the direct utilization of the property of the piezoelectric ceramic composition of being superior in piezoelectric properties. Therefore, the piezoelectric element can be utilized as a piezoelectric sensor having a high sensitivity, a piezoelectric vibrator and actuator having a high electromechanical energy conversion efficiency, etc.

According to a 24th aspect of the invention, there is provided a piezoelectric element having a piezoelectric body comprised of a piezoelectric ceramic composition produced by the method of production of the 21st or 22nd aspect of the invention.

The piezoelectric element of the 24th aspect of the invention has a piezoelectric body comprised of a piezoelectric ceramic composition obtained by the above method of production. Therefore, the piezoelectric element directly utilizes the superior properties of the piezoelectric ceramic composition, is superior in mechanical properties, and can be utilized as a piezoelectric sensor having a high sensitivity, a piezoelectric vibrator and actuator having a high electromechanical energy conversion efficiency, etc.

According to a 25th aspect of the invention, there is provided a dielectric element having a dielectric body comprised of a piezoelectric ceramic composition of the 20th aspect of the invention.

The dielectric element of the 25th aspect of the invention has a dielectric body comprised of the piezoelectric ceramic composition of the 20th aspect of the invention. Therefore, the dielectric element does not contain lead and is safe to the environment. Further, the dielectric element enables the direct utilization of the properties of the piezoelectric ceramic composition, is superior in mechanical strength, and is superior in relative dielectric constant and other dielectric properties. Therefore, the dielectric element can be utilized as a capacitor with a large electrostatic capacity.

According to a 26th aspect of the invention, there is provided a dielectric element having a dielectric body comprised of a piezoelectric ceramic composition produced by the method of production of the 21st or 22nd aspect of the invention.

The dielectric element of the 26th aspect of the invention has a dielectric body comprised of a piezoelectric ceramic composition obtained by the above method of production. Therefore, the dielectric element directly utilizes the superior properties of the piezoelectric ceramic composition, is superior in mechanical strength, and can be utilized as a capacitor with a large electrostatic capacity etc.

(5) Means for Solving the Problem V

According to a 27th aspect of the invention, there is provided a piezoelectric ceramic composition having a compound of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2 as a main ingredient, wherein the piezoelectric ceramic composition contains at least one metal element selected from magnesium, calcium, strontium, and barium as an added element, and a total of the contents of the added elements is 0.0001 mol to 0.10 mol with respect to 1 mole of the compound of the above general formula.

The above additive may be added to the above piezoelectric ceramic composition having the general formula by substitutional addition or external addition.

Further, according to a 28th aspect of the invention, there is provided a piezoelectric ceramic composition having a compound of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2 as a main ingredient, wherein the piezoelectric ceramic composition contains at least one metal element selected from silicon, indium, and scandium as an added element, and a total of the contents of the added elements is not more than 0.08 mol with respect to 1 mole of the compound of the above general formula.

The above additive may be added to the above piezoelectric ceramic composition having the general formula by substitutional addition or external addition.

Preferably, the total of the contents of said added elements is 0.0001 mol to 0.08 mol with respect to 1 mole of the compound of the above general formula.

Further, according to a 29th aspect of the invention, there is provided a piezoelectric ceramic composition having a compound of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2 as a main ingredient, wherein the piezoelectric ceramic composition contains bismuth as an added element, and a content of the added element is 0.0001 mol to 0.004 mol with respect to 1 mole of the compound of the above general formula.

The above additive may be added to the above piezoelectric ceramic composition having the general formula by substitutional addition or external addition.

Next, the action and effects of the 27th to 29th aspects of the present invention will be explained. The piezoelectric ceramic composition of each of the 27th to 29th aspects of the present invention is a composition not containing lead. Therefore, the piezoelectric ceramic composition is safe in that its waste etc. do not leach harmful lead into the natural world.

Further, the piezoelectric ceramic composition of each aspect contains the compound of the above general formula and has the x, y, z, and w in the above general formula in the above ranges. Therefore, the piezoelectric ceramic composition is superior in the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, mechanical quality factor Qm, and other piezoelectric properties, the relative dielectric constant ∈_33τ/∈₀, dielectric loss tanδ, and other dielectric properties, and Curie temperature Tc. Note that a composition of the above general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃not containing the above added elements will be referred to below as the “basic composition”.

The piezoelectric ceramic composition of the 27th aspect of the invention contains, in addition to the compound of the basic composition of the above general formula, at least one type of metal element selected from magnesium, calcium, strontium, and barium as added elements in a total in the above range of content. The piezoelectric ceramic composition of the 28th aspect of the invention contains, in addition to the compound of the basic composition of the above general formula, at least one type of metal element selected from silicon, indium, and scandium as added elements in a total in the above range of content. The piezoelectric ceramic composition of the 29th aspect of the invention contains, in addition to the compound of the basic composition of the above general formula, bismuth as an added element in the above range of content.

Therefore, the piezoelectric ceramic composition of each of the 27th to 29th aspects of the invention is further improved in at least one property among the piezoelectric d₃₁constant, piezoelectric g₃₁constant, electromechanical coupling coefficient Kp, and relative dielectric constant ∈_33τ/∈o and is more superior even compared with a piezoelectric ceramic composition of the above general formula not containing the added elements.

In this way, the piezoelectric ceramic composition of each of the 27th to 29th aspects of the invention does not contain lead and therefore is safe to the environment and further has superior piezoelectric properties, so can be utilized as a high performance piezoelectric element.

Further, the piezoelectric ceramic composition of each aspect is superior in the relative dielectric constant, dielectric loss, and other dielectric properties in addition to the above piezoelectric properties. Therefore, the piezoelectric ceramic composition of each of the 27th to 29th aspects of the invention can be utilized as a high performance dielectric element as well. That is, the piezoelectric ceramic composition of each aspect is not limited to a piezoelectric ceramic composition having piezoelectric properties and includes in concept a dielectric ceramic composition having dielectric properties as well.

According to a 30th aspect of the invention, there is provided a method of production of a piezoelectric ceramic composition comprising mixing and sintering a compound of a general formula {Li_x(K_1-yNa_y)_1-z}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2 and an additive including at least one metal element selected from magnesium, calcium, strontium, and barium.

The above additive may be added to the above piezoelectric ceramic composition having the general formula by substitutional addition or external addition.

According to a 31st aspect of the invention, there is provided a method of production of a piezoelectric ceramic composition comprising mixing and sintering a compound of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2 and an additive including at least one metal element selected from silicon, indium, and scandium.

The above additive may be added to the above piezoelectric ceramic composition having the general formula by substitutional addition or external addition.

According to a 32nd aspect of the invention, there is provided a method of production of a piezoelectric ceramic composition comprising mixing and sintering a compound of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2 and an additive including bismuth.

The above additive may be added to the above piezoelectric ceramic composition having the general formula by substitutional addition or external addition.

The mixture obtained by mixing the compound of the above general formula and the above additive in each of the 30th to 32nd aspects of the invention can be sintered under ordinary pressure. Therefore, it is possible to fire it simply and at a low cost. Further, the piezoelectric ceramic composition obtained after sintering does not contain lead and is superior in piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, and other piezoelectric properties or relative dielectric constant, dielectric loss, and other dielectric properties. Therefore, it can be used as a material for a high performance piezoelectric element or dielectric element.

Further, in the 30th aspect of the invention, the piezoelectric ceramic composition obtained after sintering has the above additive added to it, so has at least part of at least one type of the lithium, potassium, sodium, niobium, tantalum, and antimony of the compound of the above general formula substituted by at least one type of metal element selected from magnesium, calcium, strontium, and barium or has the above metal elements or oxides or perovskite structure compounds containing the same included in the grains or at the grain boundaries of the piezoelectric ceramic composition.

Further, in the 31st aspect of the invention, the piezoelectric ceramic composition obtained after sintering has the above additive added to it, so has at least part of at least one type of the lithium, potassium, sodium, niobium, tantalum, and antimony of the compound of the above general formula substituted by at least one type of metal element selected from silicon, indium, and scandium or has the above metal elements or oxides or perovskite structure compounds containing the same included in the grains or at the grain boundaries of the piezoelectric ceramic composition.

Further, in the 32nd aspect of the invention, the piezoelectric ceramic composition obtained after sintering has the above additive added to it, so has at least part of at least one type of the lithium, potassium, sodium, niobium, tantalum, and antimony of the compound of the above general formula substituted by bismuth or has the bismuth or oxides or perovskite structure compounds containing the same included in the grains or at the grain boundaries of the piezoelectric ceramic composition.

According to a 33rd aspect of the invention, there is provided a method of production of a piezoelectric ceramic composition comprising preparing a compound containing lithium, a compound containing sodium, a compound containing potassium, a compound containing niobium, a compound containing tantalum, and a compound containing antimony by a stoichiometric ratio giving, after sintering, a compound of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2 or a stoichiometric ratio considering substitution by a metal element contained in the following additive, mixing an additive containing at least one metal element selected from magnesium, calcium, strontium, and barium, and sintering the result.

According to a 34th aspect of the invention, there is provided a method of production of a piezoelectric ceramic composition comprising preparing a compound containing lithium, a compound containing sodium, a compound containing potassium, a compound containing niobium, a compound containing tantalum, and a compound containing antimony by a stoichiometric ratio giving, after sintering, a compound of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2 or a stoichiometric ratio considering substitution by a metal element contained in the following additive, mixing an additive containing at least one metal element selected from silicon, indium, and scandium, and sintering the result.

According to a 35th aspect of the invention, there is provided a method of production of a piezoelectric ceramic composition comprising preparing a compound containing lithium, a compound containing Sodium, a compound containing potassium, a compound containing niobium, a compound containing tantalum, and a compound containing antimony by a stoichiometric ratio giving, after sintering, a compound of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2 or a stoichiometric ratio considering substitution by a metal element contained in the following additive, mixing an additive containing bismuth, and sintering the result.

According to the 33rd, 34th, and 35th aspects of the invention, it is possible to simply fabricate piezoelectric ceramic compositions of the 27th, 28th, and 29th aspects of the invention. Further, in the 33rd, 34th, and 35th aspects of the invention, the compositions can be sintered at ordinary pressure. Therefore, the piezoelectric ceramic compositions can be produced simply and at a low cost. Further, the piezoelectric ceramic compositions obtained after sintering do not contain lead and are superior in piezoelectric properties and dielectric properties. Therefore, they can be utilized as materials for a high performance piezoelectric element or dielectric element.

Further, in the 33rd aspect of the invention, the piezoelectric ceramic composition obtained after sintering has the above additive added to it, so has at least part of at least one type of the lithium, potassium, sodium, niobium, tantalum, and antimony of the compound of the above general formula substituted by at least one type of metal element selected from magnesium, calcium, strontium, and barium or has the above metal elements or oxides or perovskite structure compounds containing the same included in the grains or at the grain boundaries of the piezoelectric ceramic composition.

Further, in the 34th aspect of the invention, the piezoelectric ceramic composition obtained after sintering has the above additive added to it, so has at least part of at least one type of the lithium, potassium, sodium, niobium, tantalum, and antimony of the compound of the above general formula substituted by at least one type of metal element selected from silicon, indium, and scandium or has the above metal elements or oxides or perovskite structure compounds containing the same included in the grains or at the grain boundaries of the piezoelectric ceramic composition.

Further, in the 35th aspect of the invention, the piezoelectric ceramic composition obtained after sintering has the above additive added to it, so has at least part of at least one type of the lithium, potassium, sodium, niobium, tantalum, and antimony of the compound of the above general formula substituted by bismuth or has the bismuth or oxides or perovskite structure compounds containing the same included in the grains or at the grain boundaries of the piezoelectric ceramic composition.

In the 33rd to 35th aspects of the invention, when mixing a compound containing lithium, a compound containing sodium, a compound containing potassium, a compound containing niobium, a compound containing tantalum, a compound containing antimony, and the above additive by a stoichiometric ratio considering substitution by metal elements included in the additive, it is possible to positively substitute at least part of at least one type of the lithium, sodium, potassium, niobium, tantalum, and antimony in the compound of the general formula with the metal elements or bismuth atoms included in the additive.

The “preparing . . . considering substitution by metal elements included in the additive” in the 33rd and 34th aspects of the invention and the “preparing . . . considering substitution by bismuth atoms included in the additive” can be realized, for example when substituting the lithium of the compound of the above general formula by a metal element or bismuth atoms of the additive, reducing the amount of the compound containing the lithium and adding and mixing in the above additive in exactly the reduced amount and, overall, by mixing by a stoichiometric ratio so as to give a compound of the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃after sintering.

When substituting the potassium, sodium, niobium, tantalum, or antimony in the above general formula as well, it is possible to realize this by reducing the amount of the compound containing the same and adding an additive containing the metal element or bismuth atoms desired to be substituted by in exactly the reduced amount.

On the other hand, by preparing a compound containing lithium, a compound containing sodium, a compound containing potassium, a compound containing niobium, a compound containing tantalum, and a compound containing antimony by a stoichiometric ratio giving a compound of the above general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃after sintering or before sintering and further mixing the above additive into this, it is possible to positively produce a piezoelectric ceramic composition containing the above metal elements or bismuth or oxides or perovskite structure compounds containing the same.

According to a 36th aspect of the invention, there is provided a piezoelectric element having a piezoelectric body comprised of a piezoelectric ceramic composition of the 27th to 29th aspects of the invention.

The piezoelectric element of the 36th aspect of the invention has a piezoelectric body comprised of the piezoelectric ceramic composition of the 27th to 29th aspect of the invention. Therefore, the piezoelectric element does not contain lead and is safe to the environment.

Further, the piezoelectric element enables the direct utilization of the property of the piezoelectric ceramic composition of being superior in properties such as the piezoelectric d₃₁constant. Therefore, the piezoelectric element can be utilized as a piezoelectric sensor having a high sensitivity or a piezoelectric element having a high electromechanical energy conversion efficiency such as a piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyrosensor, knock sensor, yaw rate sensor, air bag sensor, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, and piezoelectric ignitor.

According to a 37th aspect of the invention, there is provided a piezoelectric element having a piezoelectric body comprised of a piezoelectric ceramic composition produced by the method of production of the 30th to 35th aspects of the invention.

The piezoelectric element of the 37th aspect of the invention has a piezoelectric body comprised of a piezoelectric ceramic composition obtained by the method of production of the 30th to 35th aspects of the invention. Therefore, the piezoelectric element directly utilizes the superior properties of the piezoelectric ceramic composition and can be utilized as a piezoelectric sensor having a high sensitivity or a piezoelectric element having a high electromechanical energy conversion efficiency such as a piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyrosensor, knock sensor, yaw rate sensor, air bag sensor, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, and piezoelectric ignitor.

According to a 38th aspect of the invention, there is provided a dielectric element having a dielectric body comprised of a piezoelectric ceramic composition of the 27th to 29th aspects of the invention.

The dielectric element of the 38th aspect of the invention has a dielectric body comprised of the piezoelectric ceramic composition of the 27th to 29th aspects of the invention. Therefore, the dielectric element does not contain lead and is safe to the environment. Further, the dielectric element enables the direct utilization of the property of the piezoelectric ceramic composition of being superior in the relative dielectric constant, dielectric loss, etc. Therefore, the dielectric element can be utilized as a capacitor with a large electrostatic capacity.

According to a 39th aspect of the invention, there is provided a dielectric element having a dielectric body comprised of a piezoelectric ceramic composition produced by the method of production of the 30th to 35th aspects of the invention.

The dielectric element of the 39th aspect of the invention has a dielectric body comprised of a piezoelectric ceramic composition obtained by the method of production of the 30th to 35th aspects of the invention. Therefore, the dielectric element directly utilizes the superior properties of the piezoelectric ceramic composition and can be utilized as a capacitor with a large electrostatic capacity etc.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention will become clearer from the following description of the preferred embodiments given with reference to the attached FIG. 1 which is a view explaining the relationship between the value of y in the above general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃and the piezoelectric d₃₁constant.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described in detail below while referring to the attached figures.

(1) Invention I

In the present invention I, the piezoelectric ceramic composition is expressed by a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃and has an x, y, z, and w in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2. Here, when x>0.2, z>0.4, w>0.2, z=0, or w=0, the piezoelectric d₃₁constant and other properties unique to the piezoelectric ceramic composition drop and a piezoelectric ceramic composition having the desired properties is liable to not be able to be obtained any longer.

Further, the range of y in the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃is preferably 0≦x≦0.85.

Further, in the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃preferably z+w≦0.37. In this case, the piezoelectric d₃₁constant and other properties unique to the piezoelectric ceramic composition can be further improved.

The piezoelectric ceramic composition has piezoelectric properties and dielectric properties and can be used as a piezoelectric body and as a dielectric body. Specifically, it can be used for example as a piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyroscope, knock sensor, yaw rate sensor, air bag sensor, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, piezoelectric ignitor, etc.

In the first aspect of the invention, preferably the range of x in the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃is 0<x≦0.2. In this case, since lithium becomes an essential ingredient, the piezoelectric ceramic composition can be more easily prepared as a sintered body at the time of sintering, the piezoelectric properties can be further improved, and the Curie temperature can be further raised. This is because the inclusion of lithium as an essential ingredient in the above range causes the sintering temperature to drop, the lithium functions as a sintering aid, and sintering with little pores becomes possible.

Next, the value of x in the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃can be made x=0. In this case, the above formula is expressed by (K_1-yNa_y)(Nb_1-z-wTa_zSb_w)O₃. Further, in this case, when preparing the piezoelectric ceramic composition, since the materials do not include any compound containing the lightest weight lithium such as Li₂CO₃, when mixing the materials to prepare the piezoelectric ceramic composition, it is possible to reduce the variation in properties due to segregation of the powder materials. Further, in this case, a high relative dielectric constant and relatively large piezoelectric g constant can be realized.

Further, preferably the range of y in the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃is made 0<y≦1. In this case, it is possible to further improve the piezoelectric g₃₁constant of the piezoelectric ceramic composition. Further, the range of y is more preferably 0.05≦y≦0.75. In this case, it is possible to further improve the piezoelectric d₃₁constant and electromechanical coupling coefficient Kp of the piezoelectric ceramic composition. More preferably, 0.05≦y<0.75, 0.35≦y≦0.65, or even 0.35≦y<0.65. Most preferably 0.42≦y≦0.60.

Further, in the above general formula, the value of y may be made y=0. In this case, the general formula is expressed by {Li_xK)_1-x}(Nb_1-z-wTa_zSb_w)O₃. Further, in this case, the piezoelectric ceramic composition does not contain sodium and therefore the dielectric 1055 and the long-term stability of the dielectric loss of the piezoelectric ceramic composition can be improved.

Next, preferably the piezoelectric ceramic composition has a piezoelectric d₃₁constant of not less than 30 pm/V. In this case, it is possible to make use of the high piezoelectric d₃₁constant of at least 30 pm/V and utilize the piezoelectric ceramic composition for a high sensitivity piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyroscope, knock sensor, yaw rate sensor, air bag sensor, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, piezoelectric ignitor, etc.

If the piezoelectric d₃₁constant is less than 30 pm/V, the piezoelectric ceramic composition is liable to be unable to be utilized for a piezoelectric element requiring a superior sensitivity. Further, to obtain more sensitive superior piezoelectric sensor properties or larger piezoelectric actuator properties, the piezoelectric d₃₁constant is more preferably at least 40 pm/V. Still more preferably, it is at least 80 pm/V. Even more preferably, the piezoelectric d₃₁constant should be at least 100 pm/V.

Next, preferably the piezoelectric ceramic composition has a piezoelectric g₃₁constant of not less than 7×10⁻³Vm/N. In this case, it is possible to make use of the high piezoelectric g₃₁constant of at least 7×10⁻³Vm/N and utilize the piezoelectric ceramic composition for a superior booster ratio piezoelectric transformer, ultrasonic motor, sensor, etc.

If the piezoelectric g₃₁constant is less than 7×10⁻³Vm/N, the piezoelectric ceramic composition is liable to be unable to be utilized for a piezoelectric element requiring a superior booster ratio. Further, to obtain an element more superior in booster ratio, the piezoelectric g₃₁constant is more preferably made at least 10×10⁻³Vm/N.

Next, preferably the piezoelectric ceramic composition has an electromechanical coupling coefficient Kp of not less than 0.3. In this case, it is possible to make use of the high electromechanical coupling coefficient Kp of at least 0.3 and utilize the piezoelectric ceramic composition for a piezoelectric element superior in conversion efficiency of mechanical energy and electrical energy such as a piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyroscope, knock sensor, yaw rate sensor, air bag sensor, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, piezoelectric ignitor, etc.

If the electromechanical coupling coefficient is less than 0.3, the piezoelectric ceramic composition is liable to be unable to be utilized for a piezoelectric element requiring a superior conversion efficiency of mechanical energy and electrical energy. Further, to obtain more superior conversion efficiency of mechanical energy and electrical energy, the electromechanical coupling coefficient Kp is more preferably at least 0.34. Still more preferably, it is at least 0.4. Even more preferably, the electromechanical coupling coefficient Kp should be at least 0.5.

Next, preferably the piezoelectric ceramic composition has a dielectric loss of not more than 0.09. In this case, it is possible to make use of the low dielectric loss of not more than 0.09 and utilize the piezoelectric ceramic composition for a capacitor or other dielectric element or a piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyroscope, knock sensor, yaw rate sensor, air bag sensor, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, piezoelectric ignitor, etc.

If the dielectric loss is more than 0.09, the piezoelectric ceramic composition is liable to be unable to be utilized for a capacitor or other dielectric element or piezoelectric transformer, ultrasonic motor, etc. Further, the dielectric loss is more preferably not more than 0.035.

Next, preferably the piezoelectric ceramic composition has a relative dielectric constant of not less than 400. In this case, it is possible to make use of the high relative dielectric constant of at least 400 and utilize the piezoelectric ceramic composition for a capacitor having a large electrostatic capacity or other dielectric element.

If the relative dielectric constant is less than 400, the electrostatic capacity drops and the piezoelectric ceramic composition is liable to be unable to be utilized for a capacitor or other dielectric element. The relative dielectric constant is more preferably at least 430. Still more preferably, it is at least 600.

Next, preferably the piezoelectric ceramic composition has a Curie temperature Tc of not less than 200° C. In this case, it is possible to make use of the high Curie temperature Tc of at least 200° C. and utilize the piezoelectric ceramic composition in a high temperature environment exceeding 100° C. such as near an automobile engine. If the Curie temperature Tc is less than 200° C., if using the piezoelectric ceramic composition at a high temperature location such as near an automobile engine, the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, and other properties are liable to drop. Further, the Curie temperature Tc is more preferably at least 250° C.

Next, preferably the piezoelectric ceramic composition has a piezoelectric d₃₁constant of not less than 30 pm/V and a Curie temperature Tc of not less than 200° C. In this case, it is possible to use the piezoelectric ceramic composition in a high temperature environment of a temperature of over 100° C. as a high sensitivity sensor, ultrasonic motor, actuator, piezoelectric transformer, piezoelectric vibrator, etc.

Further, to obtain more sensitive superior piezoelectric sensor properties or larger piezoelectric actuator properties, the piezoelectric d₃₁constant is more preferably at least 40 pm/V. Still more preferably, it is at least 80 pm/V. Even more preferably, the piezoelectric d₃₁constant should be at least 100 pm/V. Further, the Curie temperature Tc is more preferably at least 250° C.

Next, preferably, the piezoelectric ceramic composition has a piezoelectric g₃₁constant of not less than 7×10⁻³Vm/N and a Curie temperature Tc of not less than 200° C. In this case, it is possible to use the piezoelectric ceramic composition in a high temperature environment of a temperature of over 100° C. as a superior booster ratio piezoelectric transformer, ultrasonic motor, sensor, etc.

Further, to obtain a more superior booster ratio, the piezoelectric g₃₁constant is more preferably at least 10×10⁻³Vm/N. Further, the Curie temperature Tc is more preferably at least 250° C.

Next, preferably, the piezoelectric ceramic composition has an electromechanical coupling coefficient Kp of not less than 0.3 and a Curie temperature Tc of not less than 200° C. In this case, it is possible to use the piezoelectric ceramic composition in a high temperature environment of a temperature of over 100° C. as a piezoelectric element superior in conversion efficiency of mechanical energy and electrical energy such as a piezoelectric actuator, piezoelectric vibrator, sensor, piezoelectric transformer, ultrasonic motor, etc.

Further, to obtain a more superior conversion efficiency of mechanical energy and electrical energy, the electromechanical coupling coefficient Kp is more preferably at least 0.34. More preferably, it should be at least 0.4. Further, the Curie temperature Tc is more preferably at least 250° C.

Next, preferably the piezoelectric ceramic composition has a dielectric loss of not more than 0.09 and a Curie temperature Tc of not less than 200° C. In this case, it is possible to use the piezoelectric ceramic composition in a high temperature environment of a temperature of over 100° C. as a capacitor or other dielectric element or a piezoelectric transformer, ultrasonic motor, sensor, etc. Further, the dielectric loss is more preferably not more than 0.035. Further, the Curie temperature Tc is more preferably at least 250° C.

Next, preferably the piezoelectric ceramic composition has a piezoelectric d₃₁constant of not less than 30 pm/V, an electromechanical coupling coefficient Kp of not less than 0.3, and a Curie temperature Tc of not less than 200° C. In this case, it is possible to use the piezoelectric ceramic composition in a high temperature environment of a temperature of over 100° C. and obtain a superior sensitivity and conversion efficiency of mechanical energy and electrical energy.

Further, to obtain more sensitive superior piezoelectric sensor properties or larger piezoelectric actuator properties, the piezoelectric d₃₁constant is more preferably at least 40 pm/V. Further, the electromechanical coupling coefficient Kp is more preferably at least 0.34.

Further, in the third aspect of the invention, the compound containing lithium includes for example Li₂CO₃, Li₂O, LiNO₃, LiOH, etc. The compound containing sodium includes Na₂CO₃, NaHCO₃, NaNO₃, etc.

Further, the compound containing potassium includes K₂CO₃, KNO₃, KNbO₃, KTaO₃, etc. The compound containing niobium includes for example Nb₂O₅, Nb₂O₃, NbO₂, etc. The compound containing tantalum includes Ta₂O₅etc. The compound containing antimony includes for example Sb₂O₅, Sb₂O₃, Sb₂O₄, etc.

Preferably, the compound containing lithium is Li₂CO₃, the compound containing sodium is Na₂CO₃, the compound containing potassium is K₂CO₃, the compound containing niobium is Nb₂O₅, the compound containing tantalum is Ta₂O₅, and the compound containing antimony is Sb₂O₅or Sb₂O₃. In this case, it is possible to easily fabricate the piezoelectric ceramic composition.

Next, in the fourth aspect of the invention, the piezoelectric element includes for example a piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyrosensor, knock sensor, yaw rate sensor, air bag sensor, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, and piezoelectric ignitor.

Next, in the fifth aspect of the invention, the dielectric element includes for example a capacitor, multilayer capacitor, etc.

(2) Invention II

In the sixth to eight aspects of the invention, the piezoelectric ceramic composition of the general formula {Li_x(K_1-yN_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃has ranges of x, y, z, and w of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2. Here, when x>0.2, z>0.4, w>0.2, z=0, or w=0, the piezoelectric d₃₁constant and other piezoelectric properties and dielectric properties drop and a piezoelectric ceramic composition having the desired properties is liable to not be able to be obtained any longer.

Further, the range of y in the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃is preferably 0≦x≦0.85.

Further, the range of x in the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃is preferably 0<x≦0.2. In this case, since lithium becomes an essential ingredient, the piezoelectric ceramic composition can be more easily sintered at the time of production, the piezoelectric properties can be further improved, and the Curie temperature Tc can be further raised. This is because the inclusion of lithium as an essential ingredient in the above range causes the sintering temperature to drop, the lithium functions as a sintering aid, and sintering with little pores becomes possible.

Further, the value of x in the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃can be made x=0. In this case, the above formula is expressed by (K_1-yNa_y)(Nb_1-z-wTa_zSb_w)O₃. Further, in this case, when preparing the piezoelectric ceramic composition, since the materials do not include any compound containing the lightest weight lithium such as Li₂CO₃, when mixing the materials to prepare the piezoelectric ceramic composition, it is possible to reduce the variation in properties due to segregation of the powder materials. Further, in this case, a high relative dielectric constant and relatively large piezoelectric g constant can be realized.

In the sixth aspect of the invention, the piezoelectric ceramic composition contains at least one type of metal element selected from palladium, silver, gold, ruthenium, rhodium, rhenium, osmium, iridium, and platinum as an added element and the total of the contents of the added elements is 0.001 mol to 0.15 mol with respect to 1 mol of the compound of the above general formula.

If the total of the contents is less than 0.001 mol or over 0.15 mol, the piezoelectric d₃₁constant etc. of the piezoelectric ceramic composition drop and a piezoelectric ceramic composition having the desired properties is liable to be unable to be obtained. Note that the contents of the added elements are the number of moles of the metal elements of palladium, silver, gold, ruthenium, rhodium, rhenium, osmium, iridium, and platinum.

The added elements may be present as the form of at least one type of metal element selected from palladium, silver, gold, ruthenium, rhodium, rhenium, osmium, iridium, and platinum substituting at least part of the lithium, potassium, sodium, niobium, tantalum, and antimony of the compound of the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃or in the form of the above metal elements, oxides or perovskite structure compounds, or other compounds containing the same present in the grains or at the grain boundaries of the piezoelectric ceramic composition.

In particular, silver, palladium, gold, and other metal elements which can become +1 or +2 values can be present substituting at least part of the lithium, potassium, sodium, niobium, tantalum, and antimony of the compound of the above general formula. On the other hand, palladium, ruthenium, rhenium, osmium, iridium, platinum, and other metal elements which can become +3 to +6 values may be present substituting at least part of the niobium, tantalum, and antimony of the compound of the above general formula. Further, by adopting such a substitution and solid solution state, the piezoelectric d₃₁constant and other properties can be further improved.

Next, preferably the piezoelectric d₃₁constant of the piezoelectric ceramic composition is larger than a piezoelectric d₃₁constant of a piezoelectric ceramic composition of the above general formula not containing the added elements. If larger than the piezoelectric d₃₁constant of a piezoelectric ceramic composition of the above general formula not containing the added elements (basic piezoelectric ceramic composition), the effects of the added elements can be sufficiently obtained and application to a piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyrosensor, knock sensor, yaw rate sensor, air bag sensor, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, and piezoelectric ignitor becomes easier.

The “larger than a piezoelectric d₃₁constant of a piezoelectric ceramic composition of the above general formula not containing the added elements” means that the piezoelectric d₃₁constant of the piezoelectric ceramic composition containing the added elements is larger than that of the basic piezoelectric ceramic composition having the basic composition of the piezoelectric ceramic composition not containing the above added elements. The same is true for the later mentioned electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, relative dielectric constant, dielectric loss, and Curie temperature Tc as well.

Next, preferably an electromechanical coupling coefficient Kp of the piezoelectric ceramic composition is larger than an electromechanical coupling coefficient Kp of a piezoelectric ceramic composition of the above general formula not containing the added elements. If larger than the electromechanical coupling coefficient Kp of a piezoelectric ceramic composition of the above general formula not containing the added elements (basic piezoelectric ceramic composition), the effects of the added elements can be sufficiently obtained and application to a piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyrosensor, knock sensor, yaw rate sensor, air bag sensor, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, and piezoelectric ignitor becomes easier.

Next, preferably a piezoelectric g₃₁constant of the piezoelectric ceramic composition is larger than a piezoelectric g₃₁constant of a piezoelectric ceramic composition of the above general formula not containing the added elements. If larger than the electromechanical coupling coefficient Kp of a piezoelectric ceramic composition of the above general formula not containing the added elements (basic piezoelectric ceramic composition), the effects of the added elements can be sufficiently obtained and application to a piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyrosensor, knock sensor, yaw rate sensor, air bag sensor, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, and piezoelectric ignitor becomes easier.

Next, preferably a relative dielectric constant of the piezoelectric ceramic composition is larger than a relative dielectric constant of a piezoelectric ceramic composition of the above general formula not containing the added elements. If larger than the relative dielectric constant of a piezoelectric ceramic composition of the above general formula not containing the added elements (basic piezoelectric ceramic composition), the effects of the added elements can be sufficiently obtained and application to a capacitor or other dielectric element becomes easier.

Next, preferably a dielectric loss of the piezoelectric ceramic composition is smaller than a dielectric loss of a piezoelectric ceramic composition of the above general formula not containing the added elements. If smaller than the dielectric loss of a piezoelectric ceramic composition of the above general formula not containing the added elements (basic piezoelectric ceramic composition), the effects of the added elements can be sufficiently obtained and application to a capacitor or other dielectric element becomes easier.

Next, preferably a Curie temperature Tc of the piezoelectric ceramic composition is larger than a Curie temperature of a piezoelectric ceramic composition of the above general formula not containing the added elements. If larger than the Curie temperature Tc of a piezoelectric ceramic composition of the above general formula not containing the added elements (basic piezoelectric ceramic composition), the effects of the added elements can be sufficiently obtained and use in a high temperature environment of over 100° C. such as near an automobile engine becomes easier.

Next, preferably the piezoelectric ceramic composition has a piezoelectric do constant of not less than 30 pm/V. In this case, it is possible to make use of the high piezoelectric d₃₁constant of at least 30 pm/V and utilize the piezoelectric ceramic composition for a high sensitivity piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyroscope, knock sensor, yaw rate sensor, air bag sensor, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, piezoelectric ignitor, etc.

Next, preferably the piezoelectric ceramic composition has a piezoelectric g31 constant of not less than 7×10⁻³Vm/N. In this case, it is possible to make use of the high piezoelectric g₃₁constant of at least 7×10⁻³Vm/N and utilize the piezoelectric ceramic composition for a superior booster ratio piezoelectric transformer, ultrasonic motor, sensor, etc.

Further, to obtain a more superior booster ratio, the piezoelectric g₃₁constant is more preferably at least 8×10⁻³Vm/N. Further, the Curie temperature Tc is more preferably at least 250° C.

Next, preferably, the piezoelectric ceramic composition has an electromechanical coupling coefficient Kp of not less than 0.3 and a Curie temperature Tc of not less than 200° C. In this case, it is possible to use the piezoelectric ceramic composition in a high temperature environment of a temperature of over 100° C as a piezoelectric element superior in conversion efficiency of mechanical energy and electrical energy such as a piezoelectric actuator, piezoelectric vibrator, sensor, piezoelectric transformer, ultrasonic motor, etc.

Next, preferably the piezoelectric ceramic composition has a dielectric loss of not more than 0.09 and a Curie temperature Tc of not less than 200° C. In this case, it is possible to use the piezoelectric ceramic composition in a high temperature environment of a temperature of over 100° C. as a capacitor or other dielectric element or a piezoelectric transformer, ultrasonic motor, sensor, etc. Further, the dielectric loss is more preferably not more than 0.035. More preferably, it should be not more than 0.02. Further, the Curie temperature Tc is more preferably at least 250° C.

Further, to obtain more sensitive superior piezoelectric sensor properties or larger piezoelectric actuator properties, the piezoelectric d₃₁constant is more preferably at least 40 pm/V. Further, the electromechanical coupling coefficient Kp is more preferably at least 0.34.

Further, in a seventh or eighth aspect of the invention, the additive includes at least one metal element selected from palladium, silver, gold, ruthenium, rhodium, rhenium, osmium, iridium, and platinum or a compound including these metal elements.

As a result of addition of the additive, the metal element contained in the additive sometimes is included in the piezoelectric ceramic composition as an added element by substitution of at least part of at least one type of the lithium, potassium, sodium, niobium, tantalum, and antimony of the compound of the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃after sintering. Further, sometimes the metal elements or oxides or perovskite structure compounds containing the metal elements are included in the grains or at the grain boundaries of the piezoelectric ceramic composition.

Further, in the eighth aspect of the invention, the compound containing lithium includes for example Li₂CO₃, Li₂O, LiNO₃, LiOH, etc. The compound containing sodium includes Na₂CO₃, NaHCO₃, NaNO₃, etc.

Preferably, the compound containing lithium is Li₂CO₃, the compound containing sodium is Na₂CO₃, the compound containing potassium is K₂CO₃, the compound containing niobium is Nb₂O₅, the compound containing tantalum is Ta₂O₅, and the compound containing antimony is Sb₂O₅or Sb₂O₃. The additive is preferably at least one type selected from PdO₂, Ag₂O, Au, Au₂O, Ru₂O, RhO, Re₂O₅, OsO₂, IrO₂₁and PtO₂. In this case, it is possible to easily fabricate the piezoelectric ceramic composition.

Next, in the ninth or 10th aspect of the invention, the piezoelectric element includes for example a piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyrosensor, knock sensor, yaw rate sensor, air bag sensor, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, and piezoelectric ignitor.

Next, in the 11th or 12th aspect of the invention, the dielectric element includes for example a capacitor, multilayer capacitor, etc.

(3) Invention III

In the 13th to 15th aspects of the invention, the piezoelectric ceramic composition of the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃has ranges of x, y, z, and w of 0<x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2. Here, when x>0.2, z>0.4, w>0.2, z=0, or w=0, the piezoelectric d₃₁constant and other piezoelectric properties and dielectric properties drop and a piezoelectric ceramic composition having the desired properties is liable to not be able to be obtained any longer.

Further, the range of y in the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃is preferably 0≦x≦0.85.

Further, the range of x in the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃is preferably 0≦x≦0.2. In this case, since lithium becomes an essential ingredient, the piezoelectric ceramic composition can be more easily sintered at the time of production, the piezoelectric properties can be further improved, and the Curie temperature Tc can be further raised. This is because the inclusion of lithium as an essential ingredient in the above range causes the sintering temperature to drop, the lithium functions as a sintering aid, and sintering with little pores becomes possible.

Further, the value of x in the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃can be made x=0. In this case, the above formula is expressed by (K_1-yNa_y)(Nb_1-z-wTa_zSb_w)O₃. Further, in this case, when preparing the piezoelectric ceramic composition, since the materials do not include any compound containing the lightest weight lithium such as Li₂CO₂, when mixing the materials to prepare the piezoelectric ceramic composition, it is possible to reduce the variation in properties due to segregation of the powder materials. Further, in this case, a high relative dielectric constant and relatively large piezoelectric g constant can be realized.

In the 13th aspect of the invention, the piezoelectric ceramic composition contains at least one type of metal element selected from nickel, iron, manganese, copper, and zinc as an added element and the total of the contents of the added elements is 0.001 mol to 0.08 mol with respect to 1 mol. of the compound of the above general formula.

If the total of the contents is less than 0.001 mol or over 0.08 mol, the piezoelectric d₃₁constant, the mechanical quality factor Qm, etc. of the piezoelectric ceramic composition drop and a piezoelectric ceramic composition having the desired properties is liable to be unable to be obtained. Note that the contents of the added elements are the number of moles of the metal elements of nickel, iron, manganese, copper, and zinc.

The added elements may be present as the form of at least one type of metal element selected from nickel, iron, manganese, copper, and zinc substituting at least part of the lithium, potassium, sodium, niobium, tantalum, and antimony of the compound of the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃or in the form of the above metal elements, oxides or perovskite structure compounds, or other compounds containing the same present in the grains or at the grain boundaries of the piezoelectric ceramic composition.

The above additive may be added to the above piezoelectric ceramic composition having the general formula by substitutional addition or external addition.

In particular, copper, nickel, iron, zinc, and other metal elements which can become +1 or +2 values can be present substituting at least part of the lithium, potassium, sodium, niobium, tantalum, and antimony of the compound of the above general formula. On the other hand, iron, manganese, and other metal elements which can become +3 to +6 values may be present substituting at least part of the niobium, tantalum, and antimony of the compound of the above general formula. Further, by adopting such a substitution and solid solution state, the piezoelectric d₃₁constant and other properties can be further improved.

Next, preferably the piezoelectric d₃₁constant of the piezoelectric ceramic composition is larger than a piezoelectric d₃₁constant of a piezoelectric ceramic composition of the above general formula not containing the added elements. The “larger than a piezoelectric d₃₁constant of a piezoelectric ceramic composition of the above general formula not containing the added elements” means that the piezoelectric d₃₁constant of the piezoelectric ceramic composition containing the added elements is larger than that of the basic piezoelectric ceramic composition having the basic composition of the piezoelectric ceramic composition and not containing the above added elements. The same is true for the later mentioned electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, mechanical quality factor Qm, relative dielectric constant, dielectric loss, and Curie temperature Tc as well.

Next, preferably a mechanical quality factor Qm of the piezoelectric ceramic composition is larger than a mechanical quality factor Qm of a piezoelectric ceramic composition of the above general formula not containing the added elements.

If the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, and mechanical quality factor Qm of the piezoelectric ceramic composition are larger than those of the basic piezoelectric ceramic composition of the above general formula not containing the added elements, the effects of the added elements can be sufficiently obtained and application to a piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyrosensor, knock sensor, yaw rate sensor, air bag sensor, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, and piezoelectric ignitor becomes easier.

If the piezoelectric d₃₁constant is less than 30 pm/V, the piezoelectric ceramic composition is liable to be unable to be utilized for a piezoelectric element of properties sufficient for practical use. Further, to obtain more sensitive superior piezoelectric sensor properties or larger piezoelectric actuator properties, the piezoelectric d₃₁constant is more preferably at least 40 pm/V. Still more preferably, it is at least 80 pm/V. Even more preferably, the piezoelectric d₃₁constant should be at least 100 pm/V.

If the electromechanical coupling coefficient is less than 0.3, the piezoelectric ceramic composition is liable to be unable to be utilized for a piezoelectric element requiring a superior conversion efficiency of mechanical energy and electrical energy. Further, to obtain more superior conversion efficiency of mechanical energy and electrical energy, the electromechanical coupling coefficient Kp is more preferably at least 0.34 Still more preferably, it is at least 0.4. Even more preferably, the electromechanical coupling coefficient Kp should be at least 0.45.

Next, preferably the piezoelectric ceramic composition has a mechanical quality factor Qm of not less than 50. In this case, it is possible to make use of the high mechanical quality factor Qm of at least 50 and utilize the piezoelectric ceramic composition for a piezoelectric element with little heat generation and superior in conversion efficiency of mechanical energy and electrical energy such as a piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyroscope, knock sensor, yaw rate sensor, air bag sensor, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, piezoelectric ignitor, etc.

If the mechanical quality factor Qm is less than 50, the piezoelectric ceramic composition is liable to be unable to be utilized for a piezoelectric element requiring a superior conversion efficiency of mechanical energy and electrical energy. Further, to obtain more superior conversion efficiency of mechanical energy and electrical energy, the mechanical quality factor Qm is more preferably at least 501 more preferably at least 60.

Further, to obtain more sensitive superior piezoelectric sensor properties or larger piezoelectric actuator properties, the piezoelectric dl constant is more preferably at least 40 pm/V. Still more preferably, it is at least 80 pm/V. Even more preferably, the piezoelectric d₃₁constant should be at least 100 pm/V. Further, the Curie temperature Tc is more preferably at least 250° C.

Further, to obtain a more superior booster ratio, the piezoelectric g₃₁constant is more preferably at least 8×10⁻³Vm/N. Further, the Curie temperature Tc is more preferably at least 250° C.

Next, preferably the piezoelectric ceramic composition has a mechanical quality factor Qm of not less than 50 and a Curie temperature TC of not less than 200° C. In this case, it is possible to use the piezoelectric ceramic composition in a high temperature environment of a temperature of over 100° C. as a piezoelectric element with little heat generation and superior in conversion efficiency of mechanical energy and electrical energy such as a piezoelectric actuator, piezoelectric vibrator, sensor, piezoelectric transformer, ultrasonic motor, etc. Further, the Curie temperature Tc is more preferably at least 250° C.

Next, preferably the piezoelectric ceramic composition has a dielectric loss of not more than 0.09 and a Curie temperature Tc of not less than 200° C. In this case, it is possible to use the piezoelectric ceramic composition in a high temperature environment of a temperature of over 100° C. as a capacitor or other dielectric element or a piezoelectric transformer, ultrasonic motor, sensor, etc. Further, the dielectric loss is more preferably not more than 0.035. More preferably, it should be not more than 0.025. Further, the Curie temperature Tc is more preferably at least 250° C.

Further, to obtain more sensitive superior piezoelectric sensor properties or larger piezoelectric actuator properties, the piezoelectric d₃₁constant is more preferably at least 40 pm/V. Further, the electromechanical coupling coefficient Kp is more preferably at least 0.34.

Further, in a 14th or 15th aspect of the invention, the additive includes at least one metal element selected from nickel, iron, manganese, copper, and zinc or a compound including these metal elements.

The above additive may be added to the above piezoelectric ceramic composition having the general formula by substitutional addition or external addition.

Further, in the 15th aspect of the invention, the compound containing lithium includes for example Li₂CO₃, Li₂O, LiNO₃, LiOH, etc. The compound containing sodium includes Na₂CO₃, NaHCO₃, NaNO₃, etc.

Preferably, the compound containing lithium is Li₂CO₃, the compound containing sodium is Na₂CO₃, the compound containing potassium is K₂CO₃, the compound containing niobium is Nb₂O₅, the compound containing tantalum is Ta₂O₅, and the compound containing antimony is Sb₂O₅or Sb₂O₃. The additive is preferably at least one type selected from NiO, Fe₂O₃, Mn₂O₅, Cu₂O, and ZnO. In this case, it is possible to easily fabricate the piezoelectric ceramic composition.

Next, in the 16th or 17th aspect of the invention, the piezoelectric element includes for example a piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyrosensor, knock sensor, yaw rate sensor, air bag sensor, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, and piezoelectric ignitor.

Next, in the 18th or 19th aspect of the invention, the dielectric element includes for example a capacitor, multilayer capacitor, etc.

(4) Invention IV

In the present invention, the compound of the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃has ranges of x, y, z, and w of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2. Here, when x>0.2, z>0.4, w>0.2, z=0, or w=0, the piezoelectric d₃₁constant and other piezoelectric properties and dielectric properties drop and a piezoelectric ceramic composition having properties able to withstand practical use is liable to not be able to be obtained any longer.

Further, the range of y in the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃is preferably 0≦x≦0.85.

In the 20th aspect of the invention, the piezoelectric ceramic composition contains at least one type of metal element selected from silver, aluminum, gold, boron, barium, bismuth, calcium, cerium, cobalt, cesium, copper, dysprosium, erbium, europium, iron, gallium, gadolinium, germanium, hafnium, holmium, indium, iridium, lanthanum, lutetium, magnesium, manganese, neodymiun, nickel, palladium, praseodymium, platinum, rubidium, rhenium, ruthenium, scandium, silicon, samarium, tin, strontium, terbium, titanium, thulium, vanadium, yttrium, ytterbium, zinc, and zirconium as an added element and the total of the contents of the added elements is 0.0005 mol to 0.15 mol with respect to 1 mol of the compound of the above general formula.

If the total of the contents is less than 0.0005 mol, the effects of the apparent density being high and the porosity and open porosity becoming low are liable to be unable to be sufficiently obtained. On the other hand, if the total of the contents is more than 0.15 mol, the sintering at the time of fabrication of the piezoelectric ceramic composition becomes difficult. Further, after sintering, a crystal phase different from the crystalline structure of the base composition appears and the apparent density of the sintered piezoelectric ceramic composition is liable to drop. Further, pores form at the front surface and interior of the piezoelectric ceramic composition, the porosity and open porosity become higher, and the mechanical strength of the piezoelectric ceramic composition is liable to drop.

Note that the contents of the added elements are the number of moles of the metal elements of silver, aluminum, gold, boron, barium, bismuth, calcium, cerium, cobalt, cesium, copper, dysprosium, erbium, europium, iron, gallium, gadolinium, germanium, hafnium, holmium, indium, iridium, lanthanum, lutetium, magnesium, manganese, neodymium, nickel, palladium, praseodymium, platinum, rubidium, rhenium, ruthenium, scandium, silicon, samarium, tin, strontium, terbium, titanium, thulium, vanadium, yttrium, ytterbium, zinc, and zirconium.

The added elements may be present as the form of at least one type of metal element selected from silver, aluminum, gold, boron, barium, bismuth, calcium, cerium, cobalt, cesium, copper, dysprosium, erbium, europium, iron, gallium, gadolinium, germanium, hafnium, holmium, indium, iridium, lanthanum, lutetium, magnesium, manganese, neodymium, nickel, palladium, praseodymium, platinum, rubidium, rhenium, ruthenium, scandium, silicon, samarium, tin, strontium, terbium, titanium, thulium, vanadium, yttrium, ytterbium, zinc, and zirconium substituting at least part of the lithium, potassium, sodium, niobium, tantalum, and antimony of the compound of the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃or in the form of the above metal elements, oxides or perovskite structure compounds, or other compounds containing the same present in the grains or at the grain boundaries of the piezoelectric ceramic composition.

In the piezoelectric ceramic composition of the present invention, no matter in which form of the above two forms the additive is contained, it is possible to similarly simultaneously obtain a superior apparent density, open porosity, and porosity.

Further, the open porosity of the piezoelectric ceramic composition is not more than 0.4 vol %. If the open porosity of the piezoelectric ceramic composition is over 0.4 vol %, the mechanical strength of the piezoelectric ceramic composition becomes insufficient and application to a piezoelectric element or dielectric element is liable to become difficult.

Next, preferably the apparent density of the piezoelectric ceramic composition is larger than the apparent density of a piezoelectric ceramic composition of the above general formula not containing the added elements. If the apparent density of the piezoelectric ceramic composition is smaller than the apparent density of a piezoelectric ceramic composition of the above general formula not containing the added elements (basic piezoelectric ceramic composition), not only cannot the effects of the additive be sufficiently obtained, but also the mechanical strength of the piezoelectric ceramic composition is liable to become insufficient.

The “larger than the apparent density of a piezoelectric ceramic composition of the above general formula not containing the added elements” means that the apparent density of the piezoelectric ceramic composition containing the added elements is larger than that of the basic piezoelectric ceramic composition having the basic composition of the piezoelectric ceramic composition not containing the above added elements.

Next, preferably at least one of the porosity and open porosity of the piezoelectric ceramic composition is smaller than the porosity or open porosity of a piezoelectric ceramic composition of the above general formula not containing the added elements. If larger than the porosity or open porosity of a piezoelectric ceramic composition of the above general formula not containing the added elements, not only cannot the effects of the additive be sufficiently obtained, but also the mechanical strength of the piezoelectric ceramic composition is liable to become insufficient.

The “smaller than the porosity or open porosity of a piezoelectric ceramic composition of the above general formula not containing the added elements” means that the porosity or open porosity of the piezoelectric ceramic composition containing the added elements is smaller than that of the basic piezoelectric ceramic composition having the basic composition of the piezoelectric ceramic composition not containing the above added elements.

Further, in a 21st or 22nd aspect of the invention, the additive includes at least one metal element selected from silver, aluminum, gold, boron, barium, bismuth, calcium, cerium, cobalt, cesium, copper, dysprosium, erbium, europium, iron, gallium, gadolinium, germanium, hafnium, holmium, indium, iridium, lanthanum, lutetium, magnesium, manganese, neodymium, nickel, palladium, praseodymium, platinum, rubidium, rhenium, ruthenium, scandium, silicon, samarium, tin, strontium, terbium, titanium, thulium, vanadium, yttrium, ytterbium, zinc, and zirconium or a compound including these metal elements.

Further, in the 22nd aspect of the invention, the compound containing lithium includes for example Li₂CO₃, Li₂O, LiNO₃, LiOH, etc. The compound containing sodium includes Na₂CO₃, NaHCO₃, NaNO₃, etc.

Preferably, the compound containing lithium is Li₂CO₃, the compound containing sodium is Na₂CO₃, the compound containing potassium is K₂CO₅, the compound containing niobium is Nb₂O₅, the compound containing tantalum is Ta₂O₅, and the compound containing antimony is Sb₂O₅or Sb₂O₃. The additive is preferably at least one type selected from Ag₂O, Al₂O₃, Au, Au₂O₃, B₂O₃, H₃BO₃, BaO, BaO₂, BaCO₃, Bi₂O₃, CaO, CaCO₃, CeO₂, Ce₂(CO₃)₃, CoO, Co₃O₄, CoCo₃, Cs₂Co₃, CuO, Cu₂O, Dy₂O₃, Er₂O₃, Eu₂O₃, Fe₂O₃, Ga₂O₃, Gd₂O₃, GeO₂, HfO₂, Ho₂O₃, In₂O₃, IrO₂, Ir₂O₃, La₂O₃, Lu₂O₃, MgO, MgC₂O₄, MnO, MnO₂, Mn₂O₃, Mn₃O₄, Nd₂O₃, Nd₂CO₃, NiO, NiCO₃, PdO, Pr₂O₃, Pr₆O₁₁, Pr₂(Co₃)₃), PtO₂, Rb₂O, Rb₂CO₃, Re₂O₇, RuO₂, Sc₂O₃, SiO₂, SiO, SiC, Sm₂O₃, SnO, SnO₂, SrO, SrCO₃, Tb₄O₇, TiO, Ti₂O₃, TiO₂, Tm₂O₃, V₂O₃, V₂O₄, V₂O₅, Y₂O₃, Y₂(CO₃)₃, Yb₂O₃, ZnO, and ZrO₂. In this case, it is possible to easily fabricate the piezoelectric ceramic composition.

Next, in the 23rd or 24th aspect of the invention, the piezoelectric element includes for example a piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyrosensor, knock sensor, yaw rate sensor, air bag sensor, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, and piezoelectric ignitor.

Next, in the 25th or 26th aspect of the invention, the dielectric element includes for example a capacitor, multilayer capacitor, etc.

(5) Invention V

In the 27th to 35th aspects of the invention, the piezoelectric ceramic composition of the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃has ranges of x, y, z, and w of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2. Here, when x>0.2, z>0.4, w>0.2, z=0, or w=0, the piezoelectric d₃₁constant and other piezoelectric properties and dielectric properties drop and a piezoelectric ceramic composition having the desired properties is liable to not be able to be obtained any longer.

Further, the range of y in the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃is preferably 0≦x≦0.85.

In the 27th aspect of the invention, the piezoelectric ceramic composition contains at least one type of metal element selected from magnesium, calcium, strontium, and barium as an added element and the total of the contents of the added elements is 0.0001 mol to 0.10 mol with respect to 1 mol of the compound of the above general formula.

The above additive may be added to the above piezoelectric ceramic composition having the general formula by substitutional addition or external addition.

If the total of the contents is less than 0-0001 mol or over 0.10 mol, the piezoelectric d₃₁constant, the electromechanical coupling coefficient Kp, the relative dielectric constant ∈_33τ/∈₀, etc. of the piezoelectric ceramic composition drop and a piezoelectric ceramic composition having the desired piezoelectric properties and dielectric properties is liable to be unable to be obtained. Note that the contents of the added elements are the number of moles of the metal elements of magnesium, calcium, strontium, and barium.

The added elements may be present as the form of at least one type of metal element selected from magnesium, calcium, strontium, and barium substituting at least part of the lithium, potassium, sodium, niobium, tantalum, and antimony of the compound of the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃. Atoms of magnesium, calcium, strontium, and barium which can become +2 values can be easily made present substituting at least part of the lithium, potassium, and sodium of the compound of the above general formula.

On the other hand, the added elements may be the above metal elements, oxides or perovskite structure compounds, or other compounds containing the same present in the grains or at the grain boundaries of the piezoelectric ceramic composition.

Preferably, the added elements are contained substituting at least part of the lithium, potassium, and sodium of the compound of the above general formula. In this case, the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, and other piezoelectric properties and relative dielectric constant ∈_33τ/∈₀and other dielectric properties of the piezoelectric ceramic composition can be further improved.

Particularly preferably, the added elements may be contained substituting at least part of the lithium, potassium, and sodium of the compound of the above general formula. In this case, the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, and other piezoelectric properties and relative dielectric constant ∈_33τ/∈₀and other dielectric properties of the piezoelectric ceramic composition can be further improved.

Particularly preferably, the at least one type of metal elements selected from magnesium, calcium, strontium, and barium serving as the added elements substitutes at least part of the potassium and/or sodium of the compound of the above general formula and the piezoelectric ceramic composition becomes a compound of the general formula {Li_x(K_1-yNa_y)_1-x-2uMa_u}(Nb_1-z-wTa_zSb_w)O₃(where, Ma is at least one type of metal element selected from magnesium, calcium, strontium, and barium and x, y, z, w, and u of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, 0<w≦0.2, 0.0005≦u≦0.1). In this case, the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, and other piezoelectric properties and relative dielectric constant ∈_33τ/∈₀and other dielectric properties of the piezoelectric ceramic composition can be further improved.

Further, in the 28th aspect of the invention, the piezoelectric ceramic composition contains at least one metal element selected from silicon, indium, and scandium as added elements and the total of the contents of the added elements is not more than 0.08 mol with respect to 1 mol of the compound of the above general formula.

The above additive may be added to the above piezoelectric ceramic composition having the general formula by substitutional addition or external addition.

If the total of the contents exceeds 0.08, the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, and other piezoelectric properties and relative dielectric constant ∈_33τ/∈₀and other dielectric properties of the piezoelectric ceramic composition drop and a piezoelectric ceramic composition having the desired piezoelectric properties and dielectric properties is liable to be unable to be obtained.

The lower limit of the total of the contents is preferably made 0.0001 mol so as to sufficiently obtain the effects of the added elements.

Note that the contents of the added elements are the number of moles of the metal elements of silicon, indium, and scandium.

The added elements may be present as the form of at least one type of metal element selected from silicon, indium, and scandium substituting at least part of the niobium, tantalum, and antimony of the compound of the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃. A metal element able to become a +3 or +4 value such as silicon, indium, and scandium may be easily present substituting at least part of the niobium, tantalum, and antimony of the compound of the above general formula.

On the other hand, the above metal elements may also be the above metal elements, oxides or perovskite structure compounds, or other compounds containing the same present in the grains or at the grain boundaries of the piezoelectric ceramic composition.

The above additive may be added to the above piezoelectric ceramic composition having the general formula by substitutional addition or external addition.

In the piezoelectric ceramic composition of the 28th aspect of the invention, no matter in which form of the above two forms the added elements are contained, it is possible to similarly obtain superior piezoelectric properties and dielectric properties.

Further, in the 29th aspect of the invention, the piezoelectric ceramic composition contains bismuth as an added element and the content of the added element is 0.0001 mol to 0.004 mol with respect to 1 mol of the compound of the above general formula.

In the piezoelectric ceramic composition of the 29th aspect of the invention, by including bismuth in the small amount of 0.0001 mol to 0.004 mol, the piezoelectric d₃₁constant and other properties are improved. If the total of the content is less than 0.0001 mol or over 0.004 mol, the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, relative dielectric constant ∈_33τ/∈₀, etc. of the piezoelectric ceramic composition drop and a piezoelectric ceramic composition having the desired piezoelectric properties and dielectric properties is liable to be unable to be obtained.

Note that the content of the added element is the number of moles of the metal element bismuth.

The added element may be present as the form of bismuth atoms substituting at least part of the niobium, tantalum, and antimony of the compound of the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃. A metal element able to become a +3 value such as bismuth may be easily present substituting at least part of the niobium, tantalum, and antimony of the compound of the above general formula.

On the other hand, the above metal element may also be the bismuth atoms, oxides or perovskite structure compounds, or other compounds containing the same present in the grains or at the grain boundaries of the piezoelectric ceramic composition.

The above additive may be added to the above piezoelectric ceramic composition having the general formula by substitutional addition or external addition.

In the piezoelectric ceramic composition of the 29th aspect of the invention, no matter in which form of the above two forms the added elements are contained, it is possible to similarly obtain superior piezoelectric properties and dielectric properties.

Next, in the 27th to 29th aspects of the invention, preferably the piezoelectric d₃₁constant of the piezoelectric ceramic composition is larger than a piezoelectric d₃₁constant of a piezoelectric ceramic composition of the above general formula not containing the added elements.

Next, preferably a piezoelectric g₃₁constant of the piezoelectric ceramic composition is larger than an piezoelectric g₃₁constant of a piezoelectric ceramic composition of the above general formula not containing the added elements.

Next, preferably a relative dielectric constant of the piezoelectric ceramic composition is larger than a relative dielectric constant of a piezoelectric ceramic composition of the above general formula not containing the added elements. If smaller than the relative dielectric constant of a piezoelectric ceramic composition of the above general formula not containing the added elements (basic piezoelectric ceramic composition), not only cannot the effects of the added elements be sufficiently obtained, but also application to a capacitor or other dielectric element becomes difficult.

Next, preferably a dielectric loss of the piezoelectric ceramic composition is smaller than a dielectric loss of a piezoelectric ceramic composition of the above general formula not containing the added elements. If larger than the dielectric loss of a piezoelectric ceramic composition of the above general formula not containing the added elements (basic piezoelectric ceramic composition), not only cannot the effects of the added elements be sufficiently obtained, but also application to a capacitor or other dielectric element becomes difficult.

Further, to obtain a more superior booster ratio, the piezoelectric g₃₁constant is more preferably at least 8×10⁻³Vm/N. Further, the Curie temperature Tc is more preferably at least 250° C.

Next, preferably the piezoelectric ceramic composition has a mechanical quality factor Qm of not less than 50 and a Curie temperature Tc of not less than 200° C. In this case, it is possible to use the piezoelectric ceramic composition in a high temperature environment of a temperature of over 100° C. as a piezoelectric element with little heat generation and superior in conversion efficiency of mechanical energy and electrical energy such as a piezoelectric actuator, piezoelectric vibrator, sensor, piezoelectric transformer, ultrasonic motor, etc. To obtain a more superior conversion efficient of mechanical energy and electrical energy, the mechanical quality factor Qm is more preferably at least 40. More preferably, it should be at least 50. Further, the Curie temperature Tc is more preferably at least 250° C.

Next, preferably the piezoelectric ceramic composition has a dielectric loss of not more than 0.09 and a Curie temperature Tc of not less than 200° C. In this case, it is possible to use the piezoelectric ceramic composition in a high temperature environment of a temperature of over 100° C. as a capacitor or other dielectric element or a piezoelectric transformer, ultrasonic motor, sensor, etc. Further, the dielectric loss is more preferably not more than 0.035. More preferably, it should be not more than 0.03. Further, the Curie temperature Tc is more preferably at least 250° C.

Further, to obtain more sensitive superior piezoelectric sensor properties or larger piezoelectric actuator properties, the piezoelectric do constant is more preferably at least 40 pm/V. Further, the electromechanical coupling coefficient Kp is more preferably at least 0.34.

Further, in a 30th or 33rd aspect of the invention, the additive includes at least one metal element selected from magnesium, calcium, strontium, and barium or a compound including these metal elements.

The metal elements included in the additive sometimes are included in the piezoelectric ceramic composition as added elements by substitution of at least part of the lithium, potassium, and sodium of the compound of the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃after sintering. Further, sometimes the metal elements or oxides or perovskite structure compounds containing the metal elements are included in the grains or at the grain boundaries of the piezoelectric ceramic composition.

Further, in a 31st or 34th aspect of the invention, the additive includes at least one type of metal element selected from silicon, indium, and scandium or a compound including these metal elements.

The above metal elements included in the additive sometimes are included in the piezoelectric ceramic composition as added elements by substitution of at least part of the niobium, tantalum, and antimony of the compound of the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃after sintering. Further, sometimes the metal elements atoms or oxides or perovskite structure compounds containing the metal elements are included in the grains or at the grain boundaries of the piezoelectric ceramic composition.

Further, in a 32nd or 35th aspect of the invention, the additive includes bismuth atoms or a compound including bismuth atoms.

The bismuth included in the additive sometimes is included in the piezoelectric ceramic composition as an added element by substitution of at least part of the niobium, tantalum, and antimony of the compound of the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃after sintering. Further, sometimes the bismuth atoms or oxides or perovskite structure compounds containing the bismuth atoms are included in the grains or at the grain boundaries of the piezoelectric ceramic composition.

Further, in the 33rd to 35th aspects of the invention, the compound containing lithium includes for example Li₂CO₃, Li₂O, LiNO₃, LiOH, etc. The compound containing sodium includes Na₂CO₃, NaHCO₃, NaNO₃, etc.

In the 33rd aspect of the invention, preferably the compound containing lithium is Li₂Co₃, the compound containing sodium is Na₂CO₃, the compound containing potassium is K₂CO₃, the compound containing niobium is Nb₂O₅, the compound containing tantalum is Ta₂O₅, the compound containing antimony is Sb₂O₅or Sb₂O₃, and the additive is at least one type selected from MgO, MgCO₃, CaO, CaCO₃, SrO, SrCO₃, BaO, and BaCO₃. In this case, it is possible to easily fabricate the piezoelectric ceramic composition of the 27th aspect of the invention.

In the 34th aspect of the invention, preferably the compound containing lithium is Li₂CO₃, the compound containing sodium is Na₂CO₃, the compound containing potassium is K₂CO₃, the compound containing niobium is Nb₂O₅, the compound containing tantalum is Ta₂O₅, the compound containing antimony is Sb₂O₅or Sb₂O₃, and the additive is at least one type selected from SiO₂, In₂O₃, and Sc₂O₃. In this case, it is possible to easily fabricate the piezoelectric ceramic composition of the 28th aspect of the invention.

In the 35th aspect of the invention, preferably the compound containing lithium is Li₂CO₃, the compound containing sodium is Na₂CO₃, the compound containing potassium is K₂CO₃, the compound containing niobium is Nb₂O₅, the compound containing tantalum is Ta₂O₅, the compound containing antimony is Sb₂O₅or Sb₂O₃, and the additive is Bi₂O₃. In this case, it is possible to easily fabricate the piezoelectric ceramic composition of the 29th aspect of the invention.

Next, in the 36th or 37th aspect of the invention, the piezoelectric element includes for example a piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyrosensor, knock sensor, yaw rate sensor, air bag sensor, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, and piezoelectric ignitor.

Next, in the 38th or 39th aspect of the invention, the dielectric element includes for example a capacitor, multilayer capacitor, etc.

EXAMPLE GROUP I

Next, piezoelectric ceramic compositions of Example Group I will be explained. In these examples, piezoelectric ceramic compositions were produced and measured in physical properties. The piezoelectric ceramic compositions of these examples were piezoelectric ceramic compositions of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and were in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2.

Next, a method of production of the piezoelectric ceramic compositions of these examples will be explained. First, as the materials of the piezoelectric ceramic compositions, over 99% purity high purity Li₂CO₃, Na₂CO₃, K₂CO₃, Nb₂O₅, Ta₂O₅, and Sb₂O₅were prepared. These materials were mixed by a stoichiometric ratio giving a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2.

Here, as shown in the later mentioned Table 1 to Table 6, x was made 0, 0.01, 0.02, 0.03, 0.04, 0.06, 0.08, 0.10, 0.15, and 0.20. Further, y was made 0, 0.05, 0.1, 0.2, 0.3, 0.4, 0.42, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.5, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.58, 0.60, 0.70, 0.75, 0.8, and 1.0. Further, z was made 0.002, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, 0.22, and 0.30. Further, w was made 0.02, 0.04, 0.05, 0.06, and 0.07.

Further, the materials blended to give each of these stoichiometric ratios were mixed in ball mills in acetone for 24 hours to prepare mixtures.

Next, the mixtures were calcined at 750° C. for 5 hours, then the calcined mixtures were pulverized by ball mills for 24 hours. Next, polyvinyl butyral was added as a binder and granules were formed.

The powders after granulation were press formed into disk shapes of a diameter of 18 mm and a thickness of 1 mm. The shaped articles were sintered at 1000 to 1300° C. for 1 hour to prepare sintered bodies. Note that the sintering temperature at this time was the temperature giving the greatest density selected from 1000° C. to 1300° C.

Next, the two surfaces of the sintered bodies after sintering were cylindrically polished, then the two surfaces of the disk samples were provided with metal electrodes by sputtering. Further, a DC voltage of 1 to 5 kV/mm was supplied between the electrodes for 10 minutes in 100° C. silicone oil to give polarization in the thickness direction and produce the piezoelectric ceramic compositions.

In this way, piezoelectric ceramic compositions having 180 types of stoichiometric compositions (Samples 1 to 180) were prepared. The stoichiometric ratios of the samples are shown in Table 1 to Table 6.

Further, in this example, to clarify the superior properties of the piezoelectric ceramic compositions, Comparisons 1 to 5 were fabricated in the following way. First, as materials of Comparison 1, at least 99% purity high purity K₂CO₃, Na₂CO₃, and Nb₂O₅were prepared. These materials were mixed by a stoichiometric ratio giving the general formula (K_0.5Na_0.5)NbO₃, then mixed by a ball mill in acetone for 24 hours to obtain a mixture. This mixture was calcined, granulated, shaped, sintered, and polarized in the same way as in Samples 1 to 161 to obtain Comparison 1.

Further, at least 99% purity high purity Li₂CO₃, K₂CO₃, Na₂CO₃, Nb₂O₆, Ta₂O₅, and Sb₂O₅were prepared and samples of the formulas {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x=0.22, y=0.50, z=0.45, and w=0.22, where x=0.22, y=0.50, z=0.10, and w=0.22, where x=0.22, y=0.50, z=0.45, and w=0.02, and where x=0.02, y=0.50, z=0.10, and w=0.22 were fabricated by similar methods as Comparisons 2, 3, 4, and 5. The chemical formulas of Comparisons 1 to 5 are shown in Table 6.

Next, Samples 1 to 180 and Comparisons 1 to 5 were measured for the piezoelectric d₃₁constant, piezoelectric g₃₁constant, electromechanical coupling coefficient Kp, Curie temperature Tc, relative dielectric constant ∈_33τ/∈₀, and dielectric loss tan δ.

Here, the piezoelectric d₃₁constant, piezoelectric g₃₁constant, and electromechanical coupling coefficient Kp were measured by the resonance-antiresonance method using an impedance analyzer. The dielectric loss and relative dielectric constant were measured by a measurement frequency of 1 kHz using an impedance analyzer. Further, for the Curie temperature Tc, the temperature of the highest relative dielectric constant was made the Curie temperature Tc. The results are shown in Table 7 to Table 12.

Samples 2, 4, 8, 15, 16, 31 to 34, 40, 41, 48, 49, 71, 72, 74, 75, 79, 80, 81, 88 to 90, 103, 104, 107, 110, 112, 115, 118, 119, 123 to 129, 133, 134, 136 to 140, 143, 145, 151, and 152 and Comparison 1 were measured for the long-term stability of the dielectric loss.

As the method for measurement of the long-term stability of the dielectric loss, first the dielectric losses tan δ of the samples and Comparison 1 after polarization were measured using an impedance analyzer at a Measurement frequency of 1 kHz in the same way as above and the values used as the initial tan δ. Further, the dielectric losses tan δ 50 days, 100 days, and 200 days after the polarization were measured and compared with the values of the initial tan δ so as to evaluate the long-term stability of the dielectric losses. The results are shown in Table 13 to Table 14.

TABLE 1

x
y
z
w

Sample 1
0
0.5
0.002
0.02

Sample 2
0.02
0.5
0.002
0.02

Sample 3
0.04
0.5
0.002
0.02

Sample 4
0.06
0.5
0.002
0.02

Sample 5
0.08
0.5
0.002
0.02

Sample 6
0.1
0.5
0.002
0.02

Sample 7
0
0.5
0.1
0.02

Sample 8
0.02
0.5
0.1
0.02

Sample 9
0.04
0.5
0.1
0.02

Sample 10
0.06
0.5
0.1
0.02

Sample 11
0.08
0.5
0.1
0.02

Sample 12
0.1
0.5
0.1
0.02

Sample 13
0.15
0.5
0.1
0.02

Sample 14
0.2
0.5
0.1
0.02

Sample 15
0
0.5
0.2
0.02

Sample 16
0.02
0.5
0.2
0.02

Sample 17
0.04
0.5
0.2
0.02

Sample 18
0.06
0.5
0.2
0.02

Sample 19
0.08
0.5
0.2
0.02

Sample 20
0.1
0.5
0.2
0.02

Sample 21
0.15
0.5
0.2
0.02

Sample 22
0.2
0.5
0.2
0.02

Sample 23
0
0.5
0.3
0.02

Sample 24
0.02
0.5
0.3
0.02

Sample 25
0.04
0.5
0.3
0.02

Sample 26
0.06
0.5
0.3
0.02

Sample 27
0.08
0.5
0.3
0.02

Sample 28
0.1
0.5
0.3
0.02

Sample 29
0.15
0.5
0.3
0.02

Sample 30
0.2
0.5
0.3
0.02

TABLE 2

x
y
z
w

Sample 31
0
0.5
0.002
0.04

Sample 32
0.02
0.5
0.002
0.04

Sample 33
0.04
0.5
0.002
0.04

Sample 34
0.06
0.5
0.002
0.04

Sample 35
0.08
0.5
0.002
0.04

Sample 36
0.1
0.5
0.002
0.04

Sample 37
0.15
0.5
0.002
0.04

Sample 38
0.2
0.5
0.002
0.04

Sample 39
0
0.5
0.1
0.04

Sample 40
0.02
0.5
0.1
0.04

Sample 41
0.04
0.5
0.1
0.04

Sample 42
0.06
0.5
0.1
0.04

Sample 43
00.8
0.5
0.1
0.04

Sample 44
0.1
0.5
0.1
0.04

Sample 45
0.15
0.5
0.1
0.04

Sample 46
0.2
0.5
0.1
0.04

Sample 47
0
0.5
0.2
0.04

Sample 48
0.02
0.5
0.2
0.04

Sample 49
0.04
0.5
0.2
0.04

Sample 50
0.06
0.5
0.2
0.04

Sample 51
0.08
0.5
0.2
0.04

Sample 52
0.1
0.5
0.2
0.04

Sample 53
0.15
0.5
0.2
0.04

Sample 54
0.2
0.5
0.2
0.04

Sample 55
0
0.5
0.3
0.04

Sample 56
0.02
0.5
0.3
0.04

Sample 57
0.04
0.5
0.3
0.04

Sample 58
0.06
0.5
0.3
0.04

Sample 59
0.08
0.5
0.3
0.04

Sample 60
0.1
0.5
0.3
0.04

Sample 61
0.15
0.5
0.3
0.04

Sample 62
0.2
0.5
0.3
0.04

TABLE 3

x
y
z
w

Sample 63
0
0.5
0.4
0.04

Sample 64
0.02
0.5
0.4
0.04

Sample 65
0.04
0.5
0.4
0.04

Sample 66
0.06
0.5
0.4
0.04

Sample 67
0.08
0.5
0.4
0.04

Sample 68
0.1
0.5
0.4
0.04

Sample 69
0.15
0.5
0.4
0.04

Sample 70
0.2
0.5
0.4
0.04

Sample 71
0
0.5
0.002
0.06

Sample 72
0.02
0.5
0.002
0.06

Sample 73
0.04
0.5
0.002
0.06

Sample 74
0.06
0.5
0.002
0.06

Sample 75
0.08
0.5
0.002
0.06

Sample 76
0.1
0.5
0.002
0.06

Sample 77
0.15
0.5
0.002
0.06

Sample 78
0.2
0.5
0.002
0.06

Sample 79
0
0.5
0.1
0.06

Sample 80
0.02
0.5
0.1
0.06

Sample 81
0.04
0.5
0.1
0.06

Sample 82
0.06
0.5
0.1
0.06

Sample 83
0.08
0.5
0.1
0.06

Sample 84
0.1
0.5
0.1
0.06

Sample 85
0.15
0.5
0.1
0.06

Sample 86
0.2
0.5
0.1
0.06

Sample 87
0
0.5
0.2
0.06

Sample 88
0.02
0.5
0.2
0.06

Sample 89
0.04
0.5
0.2
0.06

Sample 90
0.06
0.5
0.2
0.06

Sample 91
0.08
0.5
0.2
0.06

Sample 92
0.1
0.5
0.2
0.06

Sample 93
0.15
0.5
0.2
0.06

Sample 94
0.2
0.5
0.2
0.06

TABLE 4

x
y
z
w

Sample 95
0
0.5
0.3
0.06

Sample 96
0.02
0.5
0.3
0.06

Sample 97
0.04
0.5
0.3
0.06

Sample 98
0.06
0.5
0.3
0.06

Sample 99
0.08
0.5
0.3
0.06

Sample 100
0.1
0.5
0.3
0.06

Sample 101
0.15
0.5
0.3
0.06

Sample 102
0.2
0.5
0.3
0.06

Sample 103
0.02
0.5
0.012
0.04

Sample 104
0.04
0.5
0.012
0.04

Sample 105
0.06
0.5
0.012
0.04

Sample 106
0.02
0.5
0.014
0.04

Sample 107
0.04
0.5
0.014
0.04

Sample 108
0.06
0.5
0.014
0.04

Sample 109
0.02
0.5
0.016
0.04

Sample 110
0.04
0.5
0.016
0.04

Sample 111
0.06
0.5
0.016
0.04

Sample 112
0.02
0.5
0.18
0.04

Sample 113
0.04
0.5
0.18
0.04

Sample 114
0.01
0.5
0.2
0.04

Sample 115
0.03
0.5
0.2
0.04

Sample 116
0.02
0.5
0.22
0.04

Sample 117
0.04
0.5
0.22
0.04

Sample 118
0.02
0.5
0.08
0.05

Sample 119
0.04
0.5
0.08
0.05

Sample 120
0.06
0.5
0.08
0.05

Sample 121
0.02
0.5
0.1
0.05

Sample 122
0.04
0.5
0.1
0.05

Sample 123
0.06
0.5
0.1
0.05

Sample 124
0.02
0.5
0.12
0.05

Sample 125
0.04
0.5
0.12
0.05

Sample 126
0.06
0.5
0.12
0.05

Sample 127
0.02
0.5
0.14
0.05

Sample 128
0.04
0.5
0.14
0.05

Sample 129
0.06
0.5
0.14
0.05

TABLE 5

x
y
z
w

Sample 130
0.02
0.5
0.16
0.05

Sample 131
0.04
0.5
0.16
0.05

Sample 132
0.06
0.5
0.16
0.05

Sample 133
0.02
0.5
0.08
0.06

Sample 134
0.04
0.5
0.08
0.06

Sample 135
0.06
0.5
0.08
0.06

Sample 136
0.03
0.5
0.1
0.06

Sample 137
0.05
0.5
0.1
0.06

Sample 138
0.02
0.5
0.012
0.06

Sample 139
0.04
0.5
0.012
0.06

Sample 140
0.06
0.5
0.012
0.06

Sample 141
0.02
0.5
0.014
0.06

Sample 142
0.04
0.5
0.014
0.06

Sample 143
0.06
0.5
0.014
0.06

Sample 144
0.02
0.5
0.016
0.06

Sample 145
0.04
0.5
0.016
0.06

Sample 146
0.06
0.5
0.016
0.06

Sample 147
0.02
0.5
0.08
0.07

Sample 148
0.04
0.5
0.08
0.07

Sample 149
0.06
0.5
0.08
0.07

Sample 150
0.02
0.5
0.1
0.07

Sample 151
0.04
0.5
0.1
0.07

Sample 152
0.06
0.5
0.1
0.07

Sample 153
0.02
0.5
0.12
0.07

Sample 154
0.04
0.5
0.12
0.07

TABLE 6

x
y
z
w

Sample 155
0.04
0
0.1
0.06

Sample 156
0.04
0.2
0.1
0.06

Sample 157
0.04
0.4
0.1
0.06

Sample 158
0.04
0.5
0.1
0.06

Sample 159
0.04
0.6
0.1
0.06

Sample 160
0.04
0.8
0.1
0.06

Sample 161
0.04
1
0.1
0.06

Sample 162
0.04
0.05
0.1
0.06

Sample 163
0.04
0.1
0.1
0.06

Sample 164
0.04
0.3
0.1
0.06

Sample 165
0.04
0.42
0.1
0.06

Sample 166
0.04
0.44
0.1
0.06

Sample 167
0.04
0.45
0.1
0.06

Sample 168
0.04
0.46
0.1
0.06

Sample 169
0.04
0.47
0.1
0.06

Sample 170
0.04
0.48
0.1
0.06

Sample 171
0.04
0.49
0.1
0.06

Sample 172
0.04
0.51
0.1
0.06

Sample 173
0.04
0.52
0.1
0.06

Sample 174
0.04
0.53
0.1
0.06

Sample 175
0.04
0.54
0.1
0.06

Sample 176
0.04
0.55
0.1
0.06

Sample 177
0.04
0.56
0.1
0.06

Sample 178
0.04
0.58
0.1
0.06

Sample 179
0.04
0.7
0.1
0.06

Sample 180
0.04
0.75
0.1
0.06

Sample 181
0.02
0.5
0.1
0.1

Sample 182
0.02
0.5
0.1
0.2

Comp. 1
0
0.5
0
0

Comp. 2
0.22
0.5
0.45
0.22

Comp. 3
0.22
0.5
0.1
0.02

Comp. 4
0.02
0.5
0.45
0.02

Comp. 5
0.02
0.5
0.1
0.22

TABLE 7

d₃₁

Tc

(pm/V)
Kp
g₃₁(× 10⁻³Vm/N)
ε_33τ/ε₀
tanδ
(° C.)

Sample 1
52.1
0.463
12.1
486
0.032
369

Sample 2
52.9
0.444
11.3
526
0.046
394

Sample 3
69.0
0.451
10.2
810
0.040
398

Sample 4
84.3
0.457
8.7
1092
0.072
430

Sample 5
72.5
0.411
7.5
1090
0.099
441

Sample 6
49.6
0.291
5.0
1122
0.041
453

Sample 7
39.2
0.360
10.0
1193
0.026
244

Sample 8
66.4
0.446
9.5
786
0.040
335

Sample 9
88.9
0.463
8.3
1209
0.037
355

Sample 10
83.0
0.468
8.3
1124
0.040
374

Sample 11
66.4
0.404
7.3
1028
0.089
385

Sample 12
50.5
0.355
7.1
825
0.062
396

Sample 13
38.2
0.284
5.8
739
0.059
407

Sample 14
25.2
0.200
4.7
607
0.042
413

Sample 15
58.6
0.346
6.1
1090
0.037
218

Sample 16
84.0
0.450
7.5
1272
0.036
292

Sample 17
87.2
0.444
7.6
1290
0.029
270

Sample 18
67.9
0.428
7.7
996
0.029
316

Sample 19
53.4
0.389
7.5
809
0.047
331

Sample 20
45.1
0.341
6.6
775
0.029
330

Sample 21
33.6
0.275
5.8
651
0.025
343

Sample 22
28.7
0.226
4.8
679
0.129
352

Sample 23
13.0
0.076
1.2
1489
0.107
192

Sample 24
33.8
0.160
2.6
1454
0.048
214

Sample 25
63.8
0.368
5.9
1213
0.022
227

Sample 26
56.7
0.382
6.8
947
0.041
248

Sample 27
45.8
0.339
6.4
812
0.092
269

Sample 28
41.5
0.310
5.8
812
0.116
276

Sample 29
29.8
0.230
5.3
641
0.129
296

Sample 30
22.9
0.179
3.9
661
0.116
296

TABLE 8

d₃₁

Tc

(pm/V)
Kp
g₃₁(× 10⁻³Vm/N)
ε_33τ/ε₀
tanδ
(° C.)

Sample 31
86.2
0.623
16.2
603
0.032
330

Sample 32
62.9
0.478
12.7
559
0.050
346

Sample 33
65.3
0.433
9.2
798
0.059
370

Sample 34
99.8
0.484
8.0
1407
0.086
384

Sample 35
61.7
0.363
6.6
1057
0.040
399

Sample 36
55.8
0.344
6.3
1008
0.095
407

Sample 37
42.2
0.282
5.5
873
0.129
437

Sample 38
26.6
0.194
4.2
706
0.138
448

Sample 39
74.8
0.452
6.6
1275
0.029
275

Sample 40
85.4
0.465
9.5
1233
0.035
292

Sample 41
70.1
0.452
7.8
1389
0.026
309

Sample 42
76.8
0.426
7.2
1204
0.019
328

Sample 43
58.7
0.355
6.4
1043
0.031
337

Sample 44
52.9
0.342
6.0
1000
0.057
347

Sample 45
35.9
0.250
4.8
851
0.085
358

Sample 46
39.4
0.274
5.2
849
0.082
361

Sample 47
81.0
0.440
8.1
1133
0.025
209

Sample 48
108.0
0.452
7.0
1907
0.028
231

Sample 49
88.9
0.440
7.0
1437
0.018
252

Sample 50
67.7
0.416
7.0
1091
0.020
272

Sample 51
53.7
0.355
6.3
956
0.017
280

Sample 52
46.4
0.323
5.8
907
0.034
289

Sample 53
31.3
0.231
4.5
790
0.039
302

Sample 54
27.5
0.214
4.4
713
0.033
319

Sample 55
55.0
0.321
2.7
2274
0.023
140

Sample 56
81.6
0.341
4.2
2199
0.026
168

Sample 57
70.5
0.370
5.4
1478
0.019
196

Sample 58
62.3
0.376
7.0
1098
0.021
212

Sample 59
46.1
0.322
5.5
944
0.024
225

Sample 60
36.6
0.269
4.7
874
0.019
232

Sample 61
23.7
0.185
3.5
776
0.023
247

Sample 62
20.4
0.164
3.3
700
0.035
260

TABLE 9

d₃₁

Tc

(pm/V)
Kp
g₃₁(× 10⁻³Vm/N)
ε_33τ/ε₀
tanδ
(° C.)

Sample 63
4.9
0.080
0.2
3625
0.085
76

Sample 64
19.9
0.080
0.8
2656
0.032
104

Sample 65
34.8
0.179
8.0
1687
0.026
132

Sample 66
36.3
0.223
3.2
1269
0.023
150

Sample 67
41.0
0.288
4.8
972
0.018
173

Sample 68
30.1
0.226
3.8
889
0.019
177

Sample 69
22.3
0.178
3.3
757
0.016
199

Sample 70
16.1
0.129
2.5
719
0.018
201

Sample 71
66.3
0.452
9.7
769
0.040
289

Sample 72
66.8
0.435
9.2
819
0.036
307

Sample 73
86.9
0.476
8.8
1121
0.035
326

Sample 74
104.0
0.502
8.4
1399
0.018
341

Sample 75
78.9
0.400
7.3
1386
0.136
365

Sample 76
71.2
0.397
7.0
1146
0.073
389

Sample 77
67.9
0.388
7.0
1094
0.040
386

Sample 78
40.6
0.287
5.5
849
0.040
400

Sample 79
61.4
0.311
5.1
1358
0.040
227

Sample 80
85.1
0.425
7.0
1414
0.035
253

Sample 81
114.9
0.494
7.1
1841
0.027
272

Sample 82
83.6
0.444
7.0
1358
0.017
290

Sample 83
66.0
0.387
6.4
1159
0.029
306

Sample 84
54.8
0.344
6.1
1021
0.027
318

Sample 85
40.1
0.283
5.4
845
0.040
351

Sample 86
26.2
0.200
4.1
721
0.056
371

Sample 87
38.4
0.152
3.7
1175
0.037
166

Sample 88
90.6
0.346
4.4
2305
0.030
192

Sample 89
83.3
0.384
5.3
1769
0.021
216

Sample 90
68.2
0.389
5.9
1298
0.020
233

Sample 91
50.0
0.318
5.3
1060
0.018
247

Sample 92
40.5
0.272
4.7
980
0.017
249

Sample 93
32.7
0.238
4.7
784
0.025
288

Sample 94
24.4
0.181
3.5
797
0.092
296

TABLE 10

d₃₁

g₃₁(× 10⁻³

Tc

(pm/V)
Kp
Vm/N)
ε_33τ/ε₀
tanδ
(° C.)

Sample 95
0.0
0.000
0.0
3058
0.110
105

Sample 96
16.7
0.061
0.8
2422
0.065
130

Sample 97
54.8
0.258
3.5
1786
0.025
156

Sample 98
48.5
0.277
4.1
1351
0.022
173

Sample 99
38.6
0.245
3.8
1161
0.022
186

Sample 100
33.8
0.221
3.4
1109
0.022
188

Sample 101
26.9
0.200
3.8
803
0.024
248

Sample 102
22.7
0.184
3.8
670
0.023
252

Sample 103
73.5
0.426
7.9
1050
0.031
280

Sample 104
92.1
0.447
7.2
1453
0.024
302

Sample 105
80.9
0.452
7.7
1190
0.029
273

Sample 106
84.7
0.468
8.3
1150
0.030
265

Sample 107
99.4
0.480
7.7
1466
0.016
289

Sample 108
73.1
0.429
7.4
1122
0.014
307

Sample 109
90.7
0.449
7.3
1406
0.032
253

Sample 110
104.3
0.483
7.4
1597
0.019
276

Sample 111
72.3
0.428
7.3
1127
0.038
291

Sample 112
101.9
0.445
6.7
1715
0.030
245

Sample 113
89.0
0.425
6.7
1503
0.017
265

Sample 114
115.2
0.449
6.4
2024
0.024
221

Sample 115
113.4
0.488
7.3
1748
0.021
243

Sample 116
84.1
0.398
6.8
1393
0.035
221

Sample 117
89.2
0.436
6.5
1552
0.017
243

Sample 118
70.3
0.429
8.0
988
0.043
281

Sample 119
97.0
0.466
7.5
1458
0.022
297

Sample 120
86.5
0.461
7.4
1314
0.040
317

Sample 121
70.5
0.403
7.2
1099
0.033
266

Sample 122
107.2
0.473
7.1
1698
0.022
290

Sample 123
82.3
0.447
7.3
1276
0.056
309

Sample 124
74.3
0.416
7.4
1140
0.031
258

Sample 125
123.6
0.548
8.4
1665
0.024
273

Sample 126
75.2
0.422
7.0
1218
0.020
295

Sample 127
79.7
0.406
7.2
1396
0.034
248

Sample 128
103.9
0.469
7.0
1688
0.018
270

Sample 129
77.3
0.445
7.4
1183
0.012
286

TABLE 11

d₃₁

g₃₁(× 10⁻³

Tc

(pm/V)
Kp
Vm/N)
ε_33τ/ε₀
tanδ
(° C.)

Sample 130
96.5
0.434
7.1
1527
0.033
236

Sample 131
97.8
0.444
6.4
1722
0.018
253

Sample 132
74.4
0.428
6.9
1211
0.030
274

Sample 133
68.8
0.380
6.6
1177
0.033
264

Sample 134
107.5
0.487
7.1
1708
0.030
278

Sample 135
81.1
0.425
6.6
1381
0.022
294

Sample 136
105.1
0.454
7.1
1738
0.037
259

Sample 137
92.5
0.463
7.0
1497
0.014
280

Sample 138
87.8
0.416
7.1
1392
0.033
236

Sample 139
107.4
0.478
7.0
1740
0.020
260

Sample 140
79.9
0.434
6.9
1302
0.022
273

Sample 141
86.8
0.402
6.4
1527
0.032
226

Sample 142
95.5
0.431
6.1
1759
0.019
247

Sample 143
75.8
0.422
6.8
1250
0.013
265

Sample 144
106.6
0.438
6.3
1921
0.030
215

Sample 145
100.6
0.444
6.4
1761
0.016
234

Sample 146
70.1
0.397
6.4
1240
0.014
250

Sample 147
82.1
0.425
6.9
1349
0.035
240

Sample 148
107.5
0.447
6.2
1955
0.022
265

Sample 149
90.3
0.448
6.7
1532
0.028
278

Sample 150
85.3
0.416
6.4
1506
0.034
228

Sample 151
111.1
0.458
6.1
2053
0.022
256

Sample 152
78.5
0.404
6.1
1464
0.026
265

Sample 153
78.0
0.357
5.1
1725
0.037
217

Sample 154
111.5
0.457
6.0
2100
0.024
235

TABLE 12

g₃₁

d₃₁

(× 10⁻³

Tc
d₃₁

(pm/V)
Kp
Vm/N)
ε_33τ/ε₀
tanδ
(° C.)
ratio

Sample 155
36.0
0.246
4.8
846
0.041
286
0.31

Sample 156
51.9
0.305
5.3
1103
0.044
270
0.45

Sample 157
96.2
0.439
6.6
1636
0.027
270
0.84

Sample 158
114.9
0.494
7.1
1841
0.027
269
1

Sample 159
106.2
0.454
6.7
1780
0.025
270
0.92

Sample 160
25.1
0.260
7.5
377
0.036
264
0.22

Sample 161
18.0
0.222
7.5
301
0.027
265
0.16

Sample 162
40.0
0.261
4.9
910
0.042
282
0.35

Sample 163
44.0
0.275
5.1
975
0.043
278
0.38

Sample 164
80.0
0.372
6.0
1369
0.036
270
0.7

Sample 165
104.4
0.470
7.5
1582
0.024
270
0.91

Sample 166
113.4
0.483
7.2
1798
0.023
270
0.99

Sample 167
122.3
0.496
6.9
2013
0.022
270
1.06

Sample 168
126.9
0.509
7.1
2033
0.021
270
1.1

Sample 169
125.1
0.506
7.1
1980
0.021
270
1.09

Sample 170
122.2
0.488
6.6
2091
0.019
270
1.06

Sample 171
123.3
0.501
7.0
2004
0.022
270
1.07

Sample 172
123.3
0.496
6.9
2017
0.025
270
1.07

Sample 173
127.3
0.509
7.0
2051
0.020
270
1.11

Sample 174
127.5
0.503
6.9
2079
0.021
270
1.11

Sample 175
132.4
0.511
7.0
2136
0.021
270
1.15

Sample 176
124.7
0.491
6.8
2066
0.021
270
1.09

Sample 177
123.9
0.488
6.8
2045
0.023
270
1.08

Sample 178
123.0
0.485
6.9
2023
0.024
270
1.07

Sample 179
60.0
0.357
7.1
1078
0.030
267
0.52

Sample 180
45.0
0.309
7.3
727
0.033
266
0.39

Sample 181
66.2
0.239
4
1733
0.04
185.5

Sample 182
47.1
0.061
1.2
2312
0.04
80.5

Comp. 1
37.6
0.334
9.9
429
0.036
415

Comp. 2
0.5
0.027
0.0
1762
0.111
<room

temp.

Comp. 3
9.8
0.069
1.6
680
0.141
400

Comp. 4
42.6
0.193
2.3
2093
0.025
114.2

Comp. 5
13.3
0.053
0.6
2471
0.041
72

TABLE 13

tanδ

Initial
after
tanδ after
tanδ after

tanδ
50 days
100 days
200 days

Sample 2
0.046

0.132

Sample 4
0.072

0.253

Sample 5
0.099

0.432

Sample 8
0.040

0.053

Sample 15
0.037

0.038

Sample 16
0.036

0.036

Sample 31
0.032

0.041

Sample 32
0.050

0.050

Sample 33
0.059

0.088

Sample 34
0.086

0.141

Sample 40
0.035

0.033

Sample 41
0.026

0.023

Sample 48
0.028

0.029

Sample 49
0.018

0.017

Sample 71
0.040

0.040

Sample 72
0.036

0.046

Sample 74
0.018

0.020

Sample 75
0.056

0.130

Sample 79
0.038

0.035

Sample 80
0.035

0.042

Sample 81
0.027

0.024

Sample 88
0.030
0.030

Sample 89
0.021

0.019

Sample 90
0.020

0.044

Sample
0.031
0.032

103

Sample
0.024
0.24

104

TABLE 14

tanδ
tanδ

Initial
after
after
tanδ after

tanδ
50 days
100 days
200 days

Sample 107
0.016
0.017

Sample 110
0.019
0.022

Sample 112
0.030
0.029

Sample 115
0.021

0.032

Sample 118
0.043
0.043

Sample 119
0.022
0.020

Sample 123
0.056
0.059

Sample 124
0.031
0.033

Sample 125
0.024
0.020

Sample 126
0.020

0.027

Sample 127
0.034
0.034

Sample 128
0.018
0.021

Sample 129
0.012

0.014

Sample 133
0.033
0.032

Sample 134
0.030
0.030

Sample 136
0.027
0.029

Sample 137
0.014

0.015

Sample 138
0.033

0.031

Sample 139
0.020

0.025

Sample 140
0.022

0.032

Sample 143
0.013

0.012

Sample 145
0.016
0.013

Sample 151
0.022
0.023

Sample 152
0.026
0.020

Comp. 1
0.036
0.120
0.220
0.250

As will be understood from Table 6 to Table 12, Samples 1 to 13, 15 to 20, 25 to 28, 31 to 37, 39, 44, 46 to 52, 55 to 59, 67, 71 to 85, 87 to 92, 97 to 99, 103 to 154, 156 to 159, and 162 to 180 exhibited piezoelectric d₃₁constants higher than Comparison 1.

Here, Table 12 shows the various piezoelectric properties and dielectric properties when fixing the values of x, z, and w and changing the value of y in the above general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃. In Table 12, to clarify the change in the piezoelectric d₃₁constant when changing the value of y, the ratios of the values of the piezoelectric d₃₁constants of Samples 155 to 180 with respect to the value of the piezoelectric d₃₁constant when y=0.5 (sample 158) are shown as the d₃₁ratios.

Further, as will be understood from Table 5 to Table 12, Samples 1 to 5, 7 to 12, 15 to 20, 25 to 28, 31 to 36, 39 to 44, 47 to 51, 56 to 58, 71 to 78, 80 to 84, 88 to 90, 103 to 154, 157 to 159, and 164 to 179 exhibited electromechanical coupling coefficients Kp higher than Comparison 1.

Samples 1 to 159 and Samples 162 to 180 exhibited high relative dielectric constants of at least 430 and were superior to even Comparison 1.

Samples 1 to 5, 7 to 12, 16 to 20, 31 to 34, 40 to 42, 47 to 50, 58, 65, 71 to 77, 80 to 82, 103 to 111, 115, 118 to 130, 134, 136 to 139, 158, 160 to 161, 165 to 166, 168 to 169, 171, 173, and 175 and Samples 179 to 180 exhibited high piezoelectric g₃₁constants of at least 7.0×10⁻³Vm/M.

Samples 1 to 22, 24 to 54, 58 to 62, 70 to 86, 89 to 94, and 101 to 180 exhibited high Curie temperatures Tc of at least 200° C.

Samples 1 to 22, 24 to 26, 31 to 35, 39 to 74, 76 to 94, and 96 to 180 exhibited low dielectric losses tan δ of not more than 0.09.

As will be understood from Table 13 and Table 14, the dielectric losses of the samples did not rise much even after the elapse of 50 days, 100 days, and 200 days and therefore were superior in stability. As opposed to this, the dielectric loss of Comparison 1 increases to over 3-times the initial tan δ after the elapse of 50 days and over 6-times after 100 days. Further, it increased close to 7-times the initial tan δ after the elapse of 200 days. There was therefore a problem in stability.

Here, if taking note of the piezoelectric d₃₁constant, as will be understood from Table 1 to Table 12, when x=0.04, y=0.54, z=0.1, and w=0.05 (Sample 175), the piezoelectric d₃₁constant exhibited its highest value of 132.4 pm/V.

Further, as will be understood from Table 6 and Table 12, if fabricating the piezoelectric ceramic compositions while changing the value of y in the above general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃, the piezoelectric d₃₁constant changes greatly. Therefore, to make the relationship between the value of y in the above general formula and the piezoelectric d₃₁constant more readily understandable, the results of the piezoelectric d₃₁constant in Table 12 are shown in FIG. 1. FIG. 1 shows the value of y in the above general formula on the abscissa and the piezoelectric d₃₁constant on the ordinate.

As will be understood from FIG. 1, to realize a high piezoelectric d₃₁constant of at least 40 pm/V, the value of y in the above general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃is preferably made 0.05≦y≦0.75. If the range of the value of y is 0.35≦y≦0.65, it is possible to realize a high piezoelectric d₃₁constant of at least 80 pmV. Further, if the range of the value of y is 0.42≦y≦0.60, it is possible to realize an even higher piezoelectric d₃₁constant of over 100 pm/V. However, the preferable ranges of y change when the values of x, z, and w in the above general formula change.

When using the composition as a charge detection type circuit or a current detection type circuit, in general the piezoelectric d₃₁constant is proportional to the output voltage of an accelerator sensor, weight sensor, impact sensor, knock sensor, and other piezoelectric type sensors. Seen from this point, it is possible to prepare a sensor with a charge sensor output larger the higher the piezoelectric d₃₁constant of the piezoelectric ceramic composition. Further, to fabricate a sensor having properties equal to or better than Comparison 1, it can be said to be preferable to have a piezoelectric d₃₁constant of at least 30 pm/V. Further, to fabricate a high sensitivity sensor raised in the signal-to-noise ratio (SN ratio) and output voltage, the piezoelectric d₃₁constant should be at least 80 pm/V. More preferably it should be at least 100 pm/V.

Further, when using the composition as an actuator, in general the piezoelectric d₃₁constant is proportional to the generated distortion or displacement of the piezoelectric actuator. Seen from this point, it is possible to produce an actuator with a larger generated distortion or displacement the higher the piezoelectric d₃₁constant of the piezoelectric ceramic composition. Further, to fabricate an actuator having properties equal to or better than Comparison 1, it can be said preferable to have a piezoelectric d₃₁constant of at least 30 pmV. More preferably it should be at least 40 pm/V. Further, to fabricate an actuator with a large displacement, the piezoelectric d₃₁constant should be at least 80 pm/V. More preferably, it should be at least 100 pm/V.

Further, taking note of the electromechanical coupling coefficient Kp, as will be understood from Table 1 to Table 10, when x=0, y=0.5, z=0.002, and w=0.04 (Sample 31), the electromechanical coupling coefficient Kp exhibits its highest value of 0.623.

In general, the electromechanical coupling coefficient Kp is proportional to the electromechanical energy conversion efficiency of the piezoelectric transformer, ultrasonic motor, actuator, ultrasonic vibrator, etc. Seen from this viewpoint, it is possible to produce a piezoelectric transformer, ultrasonic motor, actuator, ultrasonic vibrator, etc. having a higher electromechanical energy conversion efficiency the higher the electromechanical coupling coefficient Kp of the piezoelectric ceramic composition. Further, to fabricate a piezoelectric transformer, ultrasonic motor, actuator, ultrasonic vibrator, etc. having properties equal to or better than the Comparison 1, it can be said to be preferable to have an electromechanical coupling coefficient Kp of at least 0.3. More preferably, it should be at least 0.34. Still more preferably, it should be at least 0.4. Most preferably, it should be at least 0.5.

Taking note of the Curie temperature Tc, the Curie temperatures Tc of the piezoelectric ceramic compositions of Samples 1 to 22, 24 to 54, 58 to 62, 70 to 86, 89 to 94, and 101 to 180 are high values of at least 200° C. Therefore, the piezoelectric ceramic compositions of the present example in the above composition region can be utilized as knock sensors or other high temperature sensor components, actuator components, ultrasonic motor components, etc. able to be used stably over a long period at high temperature locations such as near an automobile engine.

For further long-term stable use as a high temperature sensor component, actuator component, ultrasonic motor component, etc., the Curie temperature Tc is preferably at least 200° C. More preferably it should be at least 250° C.

Taking note of the piezoelectric g₃₁constant, as will be understood from Table 1 to Table 10, when x=0, y=0.5, z=0.002, and w=0.04 (Sample 31), the piezoelectric g₃₁constant exhibits its highest value at 16.2×10⁻³Vm/N.

The piezoelectric g₃₁constant, like the piezoelectric d₃₁constant, is proportional to the output voltage of a piezoelectric sensor, piezoelectric element, ultrasonic motor, etc. Therefore, it is possible to produce a sensor with a larger voltage sensor output the higher the piezoelectric g₃₁constant of the piezoelectric ceramic composition. Further, to fabricate a sensor having properties equal to or better than the Comparison 1, it can be said to be preferable to have a piezoelectric g₃₁constant of at least 7×10⁻³Vm/N. More preferably, it should be at least 10×10⁻³Vm/N.

Taking note of the relative dielectric constant ∈_33τ/∈₀, the relative dielectric constants ∈_33τ/∈₀of the Samples 1 to 159 and Samples 162 to 180 are high values of at least 430.

The relative dielectric constant ∈_33τ/∈₀is generally proportional to the electrostatic capacity of a multilayer capacitor or other capacitor. Seen from this point, it is possible to produce a capacitor with a larger electrostatic capacity the higher the relative dielectric constant of the piezoelectric ceramic composition. To fabricate a capacitor, it can be said to be preferable to have a relative dielectric constant of at least 400. More preferably, it should be at least 430. Still more preferably, it should be at least 600.

Taking note of the dielectric loss tan δ, the dielectric losses tan δ of the Samples 1 to 22, 24 to 26, 31 to 35, 39 to 74, 76 to 94, and 96 to 180 are low values of not more than 0.09.

The dielectric loss is proportional to the heat energy lost by a capacitor component or other capacitor, piezoelectric ultrasonic motor, piezoelectric actuator, piezoelectric transformer, or other component when applying an AC voltage to that component. Seen from this point, it is possible to fabricate a capacitor with a smaller energy loss or a piezoelectric ultrasonic motor, piezoelectric actuator, or piezoelectric transformer with a smaller heat generation the smaller the dielectric loss of the piezoelectric ceramic composition. Further, to fabricate a component with a small dielectric loss, it is preferable to have a dielectric loss of not more than 0.09. More preferably, it should be not more than 0.035.

Taking note of the long-term stability of the dielectric loss, as shown in Table 13 and Table 14, there is the defect that with a sample with a z of 0.002, that is, with an extremely small content of tantalum, the dielectric loss becomes larger if the sample is allowed to stand in the atmosphere for a long period. On the other hand, with a sample with a z greater than 0.002 and a w not equal to 0, there is little change in the dielectric loss and the value of the dielectric loss is kept to a small value of not more than 0.09 even if the sample is allowed to stand in the atmosphere for a long period of time. In this way, the dielectric loss tan δ of the piezoelectric ceramic composition of the present example of the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃wherein 0≦x≦0.2, 0≦y≦0.11, 0<z≦0.4, and 0<w≦0.2 has long-term stability.

Further, as shown in Table 12, it is learned that Comparisons 2, 3, and 5 not included in the composition region of the piezoelectric ceramic composition of the present invention all have piezoelectric d₃₁constants of low values of 0.5, 9.81, and 13.31 pm/V. Further, Comparison 4 has a piezoelectric d₃₁constant of 42.62 pm/V, but has a Curie temperature of a low 117° C. and therefore cannot be used as an auto part which requires a Curie temperature of at least 200° C.

EXAMPLE GROUP II

Next, piezoelectric ceramic compositions of Example Group II will be explained. In these examples, piezoelectric ceramic compositions were produced and measured in physical properties. The piezoelectric ceramic compositions of these examples were piezoelectric ceramic compositions containing as main ingredients compounds of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w were in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2. The piezoelectric ceramic compositions included added elements of at least one metal element selected from palladium, silver, gold, ruthenium, rhodium, rhenium, osmium, iridium, and platinum. Further, the total of the contents of the added elements was from 0.001 mol to 0.15 mol with respect to 1 mol of the compound of the above general formula.

The above additive may be added to the above piezoelectric ceramic composition having the general formula by substitutional addition or external addition.

The method of production of a piezoelectric ceramic composition of these examples comprises mixing a compound containing lithium, a compound containing sodium, a compound containing potassium, a compound containing niobium, a compound containing tantalum, and a compound containing antimony by a stoichiometric ratio giving, after sintering, a compound of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2, mixing an additive containing at least one metal element selected from palladium, silver, gold, ruthenium, rhodium, rhenium, osmium, iridium, and platinum, and sintering the result.

Next, the method of production of the piezoelectric ceramic compositions of these examples will be explained in more detail.

First, as the materials of the piezoelectric ceramic compositions, over 99% purity high purity Li₂CO₃, Na₂CO₃, K₂CO₃, Nb₂O₅, Ta₂O₃, and Sb₂O and, as the additive, PdO₂, Ag₂O, Au, RuO₂, Re₂O₇, IrO₂, and PtO₂were prepared.

Among these materials, the Li₂CO₃, Na₂CO₃, K₂CO₃, Nb₂O₅, Ta₂O₅, and Sb₂O₅were mixed by a stoichiometric ratio giving a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are x=0.04, y=0.5, z=0.1, and w=0.04, that is, a stoichiometric ratio whereby the general formula becomes {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.96Ta_0.1Sb_0.04))O₃, then the PdO₂, Ag₂O, Au, RuO₂, Re₂O₇, IrO₂, and PtO₂serving as the additives were mixed to obtain seven types of formulations.

Regarding the amounts of incorporation of these additives, the PdO₂, Ag₂O, Au, RuO₂, Re₂O₇, IrO₂, and PtO₂of the additives were included in amounts of 0.01 mol. 0.005 mol, 0.01 mol, 0.01 mol, 0.005 mol, 0.01 mol, and 0.01 mol, respectively, with respect to 1 mol of the compound {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04))O₃expected to be obtained by formulation by the above stoichiometric ratio. That is, 0.01 mol of the metal element included in each additive was incorporated.

The formulations were kneaded by ball mills in acetone for 24 hours to fabricate mixtures.

Next, the mixtures were calcined at 750° C. for 5 hours, then the calcined mixtures were pulverized by ball mills for 24 hours. Next, polyvinyl butyral was added as a binder and the results granulated.

The powders after granulation were press formed into disk shapes of a diameter of 13 mm and a thickness of 2 mm by a pressure of 2 tons/cm². The shaped articles were sintered at 1000 to 1300° C. for 1 hour to prepare sintered bodies. Note that the sintering temperature at this time was the temperature giving the greatest density by 1 hour of sintering selected from 1000° C. to 1300° C. Further, at this time, the sintered bodies were densified to a relative density of at least 98%.

In this way, seven types of piezoelectric ceramic compositions (Samples E1 to E7) were prepared. The ratios of the materials and additives in the samples are shown in Table 15.

These samples were prepared by external addition of each additive as described above.

Note that as a method different from the method of production of these examples, it is also possible to fabricate piezoelectric ceramic compositions similar to the Samples E1 to E7 by fabricating a compound of the above {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04)O₃by sintering, pulverizing this, mixing the result with the above additives, then calcining, granulating, shaping, and sintering the results in the same way as the method of production of the present examples.

Further, in Samples E1 to E7 of these examples, the PdO₂, Ag₂O, Au, RuO₂, Re₂O₇, IrO₂, or PtO₂of the additives may be contained in the grains or at the grain boundaries of the piezoelectric ceramic compositions in part in their inherent form or in the form of compounds such as perovskite structure compounds with at least one of the basic composition elements lithium, sodium, potassium, niobium, tantalum, and antimony and may be contained in part in a state with the palladium, silver, gold, ruthenium, rhodium, rhenium, osmium, iridium, and platinum, atoms substituting at least part of the lithium, potassium, sodium, niobium, tantalum, and antimony of the compound of the above {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04)O₃. In particular, metal elements which can become +1 or +2 values such as silver, palladium, and gold easily substitute at least part of the lithium, potassium, and sodium of the compound. Further, metal elements which can become +3 to +6 values such as palladium, ruthenium, rhodium, rhenium, osmium, iridium, and platinum easily substitute at least part of the niobium, tantalum, and antimony of the compound.

Next, in these examples, to clarify the superior properties of the piezoelectric ceramic compositions, comparisons (Sample C1 and Sample C2) were fabricated in the following way. First, as materials of the comparisons, at least 99% purity high purity Li₂CO₃, Na₂CO₃, K₂CO₃, Nb₂O₅, Ta₂O₄, and Sb₂O₅were prepared.

Among these materials, the K₂CO₃, Na₂CO₃, and Nb₂O₅were mixed by a stoichiometric ratio giving the above general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃wherein x=z=w=0 and y=0.5, that is, a stoichiometric ratio giving the above general formula (K_0.5Na_0.5)NbO₃, then mixed by a ball mill in acetone for 24 hours to obtain a mixture. This mixture was calcined, granulated, shaped, sintered, and polarized in the same way as in Samples E1 to E7 to obtain a piezoelectric ceramic composition as a comparison (Comparison C1). The Sample C1 was a piezoelectric ceramic composition containing (K_0.5Na_0.5)NbO₃.

Next, the Sample C2 was fabricated as follows: First, the Li₂CO₃, Na₂CO₃, K₂CO₃, Nb₂O₅, Ta₂O₅, and Sb₂O₅of the above prepared materials were mixed by a stoichiometric ratio giving the above general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃wherein x=0.04, y=0.5, z=0.1, and w=0.04 after sintering, that is, a stoichiometric ratio giving the above general formula {Li_0.04(K_0.5Na_0.5)_0.96}Nb_0.86Ta_0.1Sb_0.04)O₃, then mixed by a ball mill in acetone for 24 hours to obtain a mixture. This mixture was calcined, granulated, shaped, sintered, and polarized in the same way as in Samples E1 to E7 to obtain a piezoelectric ceramic composition as a comparison (Comparison C2). The Sample C2, in the same way as the Samples E1 to E7, was a piezoelectric ceramic composition which contained {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04)O₃as a main ingredient, but did not contain the above added elements.

The compositions of the Sample C1 and Sample C2 are shown in Table 15.

TABLE 15

Additive
Added

Composition ratio

Am't
element

of sample

added

Am't added

x
y
z
w
Comp.
(mol)
Type
(mol)

Sample E1
0.04
0.5
0.1
0.4
RuO₂
0.01
Ru
0.01

Sample E2
0.04
0.5
0.1
0.4
PdO₂
0.01
Pd
0.01

Sample E3
0.04
0.5
0.1
0.4
Ag₂O
0.005
Ag
0.01

Sample E4
0.04
0.5
0.1
0.4
Re₂O₇
0.005
Re
0.01

Sample E5
0.04
0.5
0.1
0.4
IrO₂
0.01
Ir
0.01

Sample E6
0.04
0.5
0.1
0.4
PtO₂
0.01
Pt
0.01

Sample E7
0.04
0.5
0.1
0.4
Au
0.01
Au
0.01

Sample C1
0
0.5
0
0
—
0
—
—

Sample C2
0.04
0.5
0.1
0.4
—
0
—
—

Next, the Samples E1 to E7 and Samples C1 and C2 were measured for the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, relative dielectric constant ∈_33τ/∈₀, dielectric loss tan δ, and Curie temperature Tc. The piezoelectric d₃₁constant, piezoelectric g₃₁constant, and electromechanical coupling coefficient Kp were measured by the resonance-antiresonance method using an impedance analyzer (Precision Impedance Analyzer 4294A made by Agilent Co.) The dielectric loss tan δ and relative dielectric constant ∈_33τ/∈₀were measured at a measurement frequency of 1 kHz using an impedance analyzer the same as the above. For the Curie temperature Tc, the temperature giving the highest relative dielectric constant ∈_33τ/∈₀was made the Curie temperature Tc. The results are shown in Table 16.

TABLE 16

d₃₁

g₃₁(× 10⁻³

Tc

(pm/V)
Kp
Vm/N)
ε_33τ/ε₀
tan δ
(° C.)

Sample E1
102.6
0.494
7.96
1457
0.015
315

Sample E2
122.4
0.531
8.74
1583
0.019
309

Sample E3
99.2
0.466
7.63
1467
0.023
300

Sample E4
89.4
0.436
7.51
1344
0.021
312

Sample E5
85.7
0.438
7.30
1326
0.016
313

Sample E6
111.9
0.512
8.32
1519
0.022
313

Sample E7
110.7
0.498
8.94
1399
0.019
305

Sample C1
37.6
0.334
9.9
429
0.036
415

Sample C2
96.1
0.452
7.81
1389
0.026
308

As will be understood from Table 16, the Samples E1 to E7 had superior properties compared with the conventional piezoelectric ceramic composition of the Sample C1 in the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, relative dielectric constant ∈_33τ/∈₀, and dielectric loss tan δ. Further, the Samples E1 to E7 had equal or better properties even compared with the Sample C2 in the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, relative dielectric constant ∈_33τ/∈₀, dielectric loss tan δ, and Curie temperature Tc. In particular, for the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, and relative dielectric constant ∈_33τ/∈₀, almost all of the Samples E1 to E7 were superior to the Sample C1 and the Sample C2, while for the dielectric loss tan δ, all of the Samples E1 to E7 were superior to the Sample C1 and Sample C2.

Here, taking note of the piezoelectric d₃₁constant, as will be understood from Table 16, the piezoelectric d₃₁constant of the Sample E2 exhibited the highest value of 122.4 pm/V.

When using the composition as a charge detection type circuit or a current detection type circuit, in general the piezoelectric d₃₁constant is proportional to the output voltage of an accelerator sensor, weight sensor, impact sensor, knock sensor, and other piezoelectric type sensors. Seen from this point, it is possible to prepare a sensor with a charge sensor output larger the higher the piezoelectric d₃₁constant of the piezoelectric ceramic composition. Further, to fabricate a sensor having properties equal to or better than Sample C1, it can be said to be preferable to have a piezoelectric d₃₁constant of at least 30 pm/V. Further, to fabricate a high sensitivity sensor raised in the signal-to-noise ratio (SN ratio) and output voltage, the piezoelectric d₃₁constant should be at least 80 pm/V. More preferably it should be at least 100 pm/V.

Further, when using the composition as an actuator, in general the piezoelectric d₃₁constant is proportional to the generated distortion or displacement of the piezoelectric actuator. Seen from this point, it is possible to produce an actuator with a larger generated distortion or displacement the higher the piezoelectric d₃₁constant of the piezoelectric ceramic composition. Further, to fabricate an actuator having properties equal to or better than the comparison, it can be said preferable to have a piezoelectric d₃₁constant of at least 30 pmV. More preferably it should be at least 40 pm/V. Further, to fabricate an actuator with a large displacement, the piezoelectric d₃₁constant should be at least 80 pm/V. More preferably, it should be at least 100 pm/V.

Further, taking note of the electromechanical coupling coefficient Kp, as will be understood from Table 16, the electromechanical coupling coefficient Kp of Sample E2 exhibits its highest value of 0.531.

In general, the electromechanical coupling coefficient Kp is proportional to the electromechanical energy conversion efficiency of the piezoelectric transformer, ultrasonic motor, actuator, ultrasonic vibrator, etc. Seen from this viewpoint, it is possible to produce a piezoelectric transformer, ultrasonic motor, actuator, ultrasonic vibrator, etc. having a higher electromechanical energy conversion efficiency the higher the electromechanical coupling coefficient Kp of the piezoelectric ceramic composition. Further, to fabricate a piezoelectric transformer, ultrasonic motor, actuator, ultrasonic vibrator, etc. having properties equal to or better than the comparison Sample C1, it can be said to be preferable to have an electromechanical coupling coefficient Kp of at least 0.3. More preferably, it should be at least 0.34. Still more preferably, it should be at least 0.4. Most preferably, it should be at least 0.5.

Taking note of the Curie temperature Tc, the Curie temperatures Tc of Samples E1 to E7 are all high values of at least 200° C. Therefore, the piezoelectric ceramic compositions of the present examples (Samples E1 to E7) can be utilized as knock sensors or other high temperature sensor components, actuator components, ultrasonic motor components, etc. able to be used stably over a long period at high temperature locations such as near an automobile engine.

Taking note of the piezoelectric g₃₁constant, as will be understood from Table 16, the piezoelectric g₃₁constant of Sample E7 exhibits its highest value at 8.94×10⁻³Vm/N.

Taking note of the relative dielectric constant ∈_33τ/∈₀, the relative dielectric constants ∈_33τ/∈₀of the Samples E1 to E7 are extremely high values of at least 1300.

Taking note of the dielectric loss tan ∈, the dielectric losses tan δ of the Samples E1 to E7 are extremely low values of not more than 0.23.

As explained above, the piezoelectric ceramic compositions (Sample E1 to Sample E7) of the present examples are of compositions not containing lead and have superior piezoelectric properties and dielectric properties. Therefore, they are safe to the environment and can be utilized for high performance piezoelectric elements and dielectric elements.

EXAMPLE GROUP III

These examples are of compounds of the above general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃containing different amounts of Ag₂O as additives in order to determine the critical range of content of the additive.

First, as the materials of the piezoelectric ceramic composition, over 99% purity high purity Li₂CO₃, Na₂CO₂, K₂CO₃, Nb₂O₅, Ta₂O₅, and Sb₂O₅and, as the additive, Ag₂O were prepared.

Among these materials, the Li₂CO₃, Na₂CO₃, K₂CO₃, Nb₂O₅, Ta₂O₅, and Sb₂O₅were mixed by a stoichiometric ratio giving a general formula {Li_w(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are x=0.04, y=0.5, z=0.1, and w=0.06, then the Ag₂O serving as the additive was mixed n different amounts to obtain 16 types of formulations.

Regarding the amounts of incorporation of the Ag₂O, the Ag₂O of the additive was included in amounts of 0.0005 mol to 0.25 mol with respect to 1 mol of the compound {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb0.06)O₃, expected to be obtained by formulation by the above stoichiometric ratio and sintering. That is, 0.001 to 0.5 mol of the silver was incorporated.

The formulations were mixed by ball mills in acetone for 24 hours to fabricate mixtures.

Next, in the same way as Sample E1 to Sample E7 of the Example Group II, the mixtures were calcined, granulated, shaped, sintered, and polarized to prepare 16 types of piezoelectric ceramic compositions. These were used as Sample X1 to Sample X16. The ratios of the materials and additive in the samples are shown in Table 17.

Further, in Samples X1 to X16 obtained here, the Ag₂O of the additive may be contained in the grains or at the grain boundaries of the piezoelectric ceramic compositions in part in its inherent form or in the form of compounds such as perovskite structure compounds with at least one of the basic composition elements lithium, sodium, potassium, niobium, tantalum, and antimony and may be contained in part in a state with the silver in the Ag₂O substituting at least part of the lithium, potassium, and sodium of the {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04)O₃. In particular, when the amount added of the Ag₂O exceeds 0.1 mol with respect to 1 mol of the compound of the above {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04)O₃, that is, when the content of the metal element silver exceeds 0.2 mol, the Ag₂O of the additive easily precipitates in the form of silver and or Ag₂O or a compound containing silver at the grain boundaries of the piezoelectric ceramic compositions.

In these examples, to clarify the effects of the incorporation of Ag, samples were prepared by substitutional addition that part of (K_0.5Na_0.5) is substituted by Ag. For example, sample X8 had a composition of {Li_0.04(K_0.5Na_0.5)_0.86Ag_0.10}(Nb_0.84Ta_0.1Sb_0.06)O₃.

Next, in these examples, to clarify the effects of the incorporation of Ag₂O, a sample not containing Ag₂O as an additive was prepared.

Specifically, first, at least 99% purity high purity Li₂CO₃, Na₂CO₃, K₂CO₃, Nb₂O₅, Ta₂O₄, and Sb₂O₅were prepared. These materials were mixed by a stoichiometric ratio giving a compound of {Li_0.04(K_0.5Na_0.5)_0.96}(Nb0.84Ta_0.1Sb0.06)O₃, then mixed by a ball mill in acetone for 24 hours to obtain a mixture. This mixture was calcined, granulated, shaped, sintered, and polarized in the same way as in Samples E1 to E7 of the examples of the Invention II obtain a piezoelectric ceramic composition (Sample Y1). The composition of the Sample Y1 is shown in Table 17.

TABLE 17

Added

element

Composition ratio
Additive

Am't

of sample

Am't added

added

Sample
x
y
z
w
Comp.
(mol)
Type
(mol)

Sample X1
0.04
0.5
0.1
0.6
Ag₂O
0.0005
Ag
0.001

Sample X2
0.04
0.5
0.1
0.6
Ag₂O
0.0015
Ag
0.003

Sample X3
0.04
0.5
0.1
0.6
Ag₂O
0.0025
Ag
0.005

Sample X4
0.04
0.5
0.1
0.6
Ag₂O
0.005
Ag
0.01

Sample X5
0.04
0.5
0.1
0.6
Ag₂O
0.01
Ag
0.02

Sample X6
0.04
0.5
0.1
0.6
Ag₂O
0.02
Ag
0.04

Sample X7
0.04
0.5
0.1
0.6
Ag₂O
0.04
Ag
0.08

Sample X8
0.04
0.5
0.1
0.6
Ag₂O
0.05
Ag
0.01

Sample X9
0.04
0.5
0.1
0.6
Ag₂O
0.075
Ag
0.15

Sample X10
0.04
0.5
0.1
0.6
Ag₂O
0.1
Ag
0.2

Sample X11
0.04
0.5
0.1
0.6
Ag₂O
0.125
Ag
0.25

Sample X12
0.04
0.5
0.1
0.6
Ag₂O
0.15
Ag
0.3

Sample X13
0.04
0.5
0.1
0.6
Ag₂O
0.175
Ag
0.36

Sample X14
0.04
0.5
0.1
0.6
Ag₂O
0.2
Ag
0.4

Sample X15
0.04
0.5
0.1
0.6
Ag₂O
0.225
Ag
0.45

Sample X16
0.04
0.5
0.1
0.6
Ag₂O
0.25
Ag
0.5

Sample Y1
0.04
0.5
0.1
0.6
—
0

0

Next, the Samples X1 to X16 and Sample Y1 were measured for the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, relative dielectric constant ∈_33τ/∈₀, dielectric loss tan δ, and Curie temperature Tc in the same way as in the examples of the Invention II. The results are shown in Table 18. Note that Table 18 also shows the results of Sample C1 prepared in the examples of the Invention II for comparison.

TABLE 18

d₃₁

g₃₁(× 10⁻³

Tc

(pm/V)
Kp
Vm/N)
ε_33τ/ε₀
tan δ
(° C.)

Sample X1
117.2
0.495
7.19
1845.2
0.023
271

Sample X2
118.3
0.495
7.22
1849.2
0.021
271

Sample X3
119.5
0.498
7.20
1860.0
0.018
269

Sample X4
120.4
0.503
7.19
1891.2
0.016
266

Sample X5
119.1
0.496
6.97
1894.7
0.017
263

Sample X6
118.7
0.494
6.81
1891.5
0.018
257

Sample X7
118.4
0.492
6.43
1995.1
0.018
247

Sample X8
117.2
0.482
6.35
1978.9
0.019
238

Sample X9
116.1
0.450
6.00
2183.6
0.020
227

Sample X10
101.6
0.396
5.07
2262.1
0.022
213

Sample X11
51.8
0.301
2.89
2024.5
0.032
198

Sample X12
34.1
0.255
1.39
1451.2
0.035
185

Sample X13
22.3
0.220
1.01
1218.0
0.037
170

Sample X14
12.3
0.150
0.65
857.1
0.039
155

Sample X15
8.9
0.100
0.60
841.0
0.039
140

Sample X16
5.6
0.050
0.55
824.8
0.040
125

Sample C1
37.6
0.334
9.9
429
0.036
415

Sample Y1
114.9
0.494
7.05
1840.8
0.027
269

As will be understood from Table 18, the Samples X1 to X9 had a higher piezoelectric d₃₁constant and relative dielectric constant ∈_33τ/∈₀than the Sample Y1 and Sample C1. Further, the dielectric losses tan δ were also smaller than the Sample Y1 and Sample C1 and therefore superior.

That is, as will be understood from Table 17 and Table 18, when the amount of the Ag₂O added as an additive is 0.001 mol to 0.15 mol in content of the added element silver with respect to 1 mol of the compound of the above general formula, the piezoelectric ceramic composition is particularly superior in the piezoelectric d₃₁constant, relative dielectric constant ∈_33τ/∈₀, and dielectric loss tan δ.

Further, as will be understood from Table 18, the Samples X1 to X9 exhibited superior properties of about the same extent as the Sample Y1 in the electromechanical coupling coefficient Kp, pg₃₁c, and Curie temperature Tc as well.

On the other hand, in the case of Samples X10 to X16, that is, when the amounts of Ag₂O of the additive is over 0.15 mol in terms of content of the added element silver, values lower than even the Sample Y1 were exhibited in all properties such as the piezoelectric d₃₁constant and also the electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, relative dielectric constant ∈_33τ/∈₀dielectric loss tan δ, and Curie temperature Tc.

In this way, according to the present examples, it is found that when the content of the added element is 0.001 mol to 0.15 mol, the properties of the piezoelectric ceramic composition are improved the most remarkably. Note that while not shown in the table, the same effects as in these examples were obtained for the other metal elements as well.

According to our findings, the additives can effectively enhance piezoelectric properties etc. either by substitutional addition or external addition, while not shown in the present examples. Further, the same effect as in these examples were obtained for the other piezoelectric ceramic compositions containing other main ingredients compounds.

EXAMPLE GROUP IV

Next, the piezoelectric ceramic compositions of Example Group IV will be explained. In these examples, piezoelectric ceramic compositions were produced and measured in physical properties. The piezoelectric ceramic compositions of these examples were piezoelectric ceramic compositions containing as main ingredients compounds of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w were in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2. The piezoelectric ceramic compositions included added elements of at least one metal element selected from nickel, iron, manganese, copper, and zinc. Further, the total of the contents of the added elements was from 0.001 mol to 0.08 mol with respect to 1 mol of the compound of the above general formula.

Next, the method of production of the piezoelectric ceramic compositions of these examples will be explained in more detail.

First, as the materials of the piezoelectric ceramic compositions, over 99% purity high purity Li₂CO₃, Na₂CO₃, K₂CO₃, Nb₂O₅, Ta₂O₅, and Sb₂O₅and, as the additive, NiO, Fe₂O₃, Mn₂O₅, Cu₂O, and ZnO were prepared.

Among these materials, the Li₂CO₃, Na₂CO₃, K₂CO₃, Nb₂O₅, Ta₂O₅, and Sb₂O₅were mixed by a stoichiometric ratio giving a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are x=0.04, y=0.5, z=0.1, and w=0.04, that is, a stoichiometric ratio whereby the general formula becomes {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04))O₃, then the NiO, Fe₂O₃, Mn₂O₅, Cu₂O, and ZnO serving as the additives were mixed to obtain five types of formulations.

Regarding the amounts of incorporation of these additives, the NiO, Fe₂O₃, Mn₂O₅, Cu₂O, and ZnO of the additives were included in amounts of 0.01 mol, 0.005 mol, 0.005 mol, 0.005 mol, and 0.01 mol, respectively, with respect to 1 mol of the compound {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04))O₃expected to be obtained by formulation by the above stoichiometric ratio. That is, 0.01 mol of the metal element included in each additive was incorporated.

The formulations were kneaded by ball mills in acetone for 24 hours to fabricate mixtures.

Next, the mixtures were calcined at 750° C. for 5 hours, then the calcined mixtures was pulverized by ball mills for 24 hours. Next, polyvinyl butyral was added as a binder and the results granulated.

In this way, five types of piezoelectric ceramic compositions (Samples D1 to D5) were prepared. The ratios of the materials and additives in the samples are shown in Table 19.

These samples were prepared by external addition of each additive as described above.

Note that as a method different from the method of production of these examples, it is also possible to fabricate piezoelectric ceramic compositions similar to the Samples D1 to D5 by fabricating a compound of the above {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04)O₃by sintering, pulverizing this, mixing the result with the above additives, then calcining, granulating, shaping, and sintering the results in the same way as the method of production of the present examples.

Further, in Samples D1 to D5 of these examples, the NiO, Fe₂O₃, Mn₂O₅, Cu₂O, and ZnO of the additives may be contained in the grains or at the grain boundaries of the piezoelectric ceramic compositions in part in their inherent form or in the form of compounds such as perovskite structure compounds with at least one of the basic composition elements lithium, sodium, potassium, niobium, tantalum, and antimony and may be contained in part in a state with the nickel, iron, manganese, copper, and zinc atoms substituting at least part of the lithium, potassium, sodium, niobium, tantalum, and antimony of the compound of the above {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04)O₃. In particular, metal elements which can become +1 or +2 values such as copper, nickel, iron, and zinc easily substitute at least part of the lithium, potassium, and sodium of the compound. Further, metal elements which can become +3 to +6 values such as iron and manganese easily substitute at least part of the niobium, tantalum, and antimony of the compound.

Next, in these examples, to clarify the superior properties of the piezoelectric ceramic compositions, comparisons (Sample C1 and Sample C2) were fabricated in the same way as in Example Group II. The compositions of the Sample C1 and Sample C2 are shown in Table 19.

TABLE 19

Added

Additive
element

Composition ratio of

Am't

Am't

sample

added

added

x
y
z
w
Comp.
(mol)
Type
(mol)

Sample D1
0.04
0.5
0.1
0.4
Fe₂O₃
0.005
Fe
0.01

Sample D2
0.04
0.5
0.1
0.4
NiO
0.01
Ni
0.01

Sample D3
0.04
0.5
0.1
0.4
Mn₂O₅
0.005
Mn
0.01

Sample D4
0.04
0.5
0.1
0.4
ZnO
0.01
Zn
0.01

Sample D5
0.04
0.5
0.1
0.4
Cu₂O
0.005
Cu
0.01

Sample C1
0
0.5
0
0
—
0
—
0

Sample C2
0.04
0.5
0.1
0.4
—
0
—
0

Next, the Samples D1 to D5 and Samples C1 and C2 were measured for the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, mechanical quality factor Qm, relative dielectric constant ∈_33τ/∈₀, dielectric loss tan δ, and Curie temperature Tc. The piezoelectric d₃₁constant, piezoelectric g₃₁constant, electromechanical coupling coefficient Kp, and mechanical quality factor Qm were measured by the resonance-antiresonance method using an impedance analyzer (Precision Impedance Analyzer 4294A made by Agilent Co.) The dielectric loss tan δ and relative dielectric constant ∈_33τ/∈₀were measured at a measurement frequency of 1 kHz using an impedance analyzer the same as the above. For the Curie temperature Tc, the temperature giving the highest relative dielectric constant ∈_33τ/∈₀was made the Curie temperature Tc. The results are shown in Table 20.

TABLE 20

g₃₁

d₃₁

(× 10⁻³

TC

(pm/V)
Kp
Vm/N)
Qm
ε_33τ/ε₀
tanδ
(° C.)

Sample D1
100.5
0.484
8.06
56.4
1408.1
0.022
299

Sample D2
98.6
0.496
8.63
94.6
1290.4
0.018
312

Sample D3
86.5
0.424
6.99
67.5
1398.3
0.019
311

Sample D4
79.3
0.429
7.61
56.7
1176.7
0.020
311

Sample D5
72.7
0.419
7.82
136.5
1049.3
0.007
301

Sample C1
37.6
0.334
9.9
100.6
329
0.036
415

Sample C2
96.1
0.452
7.81
48.4
1389.3
0.026
308

As will be understood from Table 20, the Samples D1 to D5 had superior properties compared with the conventional piezoelectric ceramic composition of the Sample C1 in the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, mechanical quality factor Qm, relative dielectric constant ∈_33τ/∈₀, and dielectric loss tan δ. Further, the Samples D1 to D5 had equal or better properties even compared with the Sample C2 in the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, mechanical quality factor Qm, relative dielectric constant ∈_33τ/∈₀, dielectric loss tan δ, and Curie temperature Tc. Further, as will be understood from Table 20, the Samples D1 to D5 had high mechanical quality factors Qm of at least 50 while maintaining high piezoelectric d₃₁constants of at least 70 pm/V and therefore were superior in both the piezoelectric d₃₁constant and the mechanical quality factor Qm. Therefore, the Sample D1 to Sample D5 can be used as high performance piezoelectric elements.

Here, taking note of the piezoelectric d₃₁constant, as will be understood from Table 20, the piezoelectric d₃₁constant of the Sample D1 exhibited the highest value of 100.5 pm/V.

When using the composition as a charge detection type circuit or a current detection type circuit, in general the piezoelectric d₃₁constant is proportional to the output voltage of an accelerator sensor, weight sensor, impact sensor, knock sensor, and other piezoelectric type sensors. Seen from this point, it is possible to prepare a sensor with a charge sensor output larger the higher the piezoelectric d₃₁constant of the piezoelectric ceramic composition. Further, to fabricate a sensor having properties equal to or better than Sample C1, it can be said to be preferable to have a piezoelectric d₃₁constant of at least 30 pm/V. Further, to fabricate a high sensitivity sensor raised in the signal-to-noise ratio (SN ratio) and output voltage, the piezoelectric d₃₁constant should be at least 80 pm/V. More preferably it should be at least 100 pm/V.

Further, when using the composition as an actuator, in general the piezoelectric d₃₁constant is proportional to the generated distortion or displacement of the piezoelectric actuator. Seen from this point, it is possible to produce an actuator with a larger generated distortion or displacement the higher the piezoelectric d₃₁constant of the piezoelectric ceramic composition. Further, to fabricate an actuator having properties equal to or better than the comparison, it can be said preferable to have a piezoelectric d₃₁constant of at least 30 pmV. More preferably it should be at least 40 pm/V. Further, to fabricate an actuator with a large displacement, the piezoelectric d₃₁constant should be at least 80 pm/V. More preferably, it should be at least 100 pm/V.

Further, taking note of the electromechanical coupling coefficient Kp, as will be understood from Table 20, the electromechanical coupling coefficient Kp of Sample D2 exhibits its highest value of 0.496.

In general, the electromechanical coupling coefficient Kp is proportional to the electromechanical energy conversion efficiency of the piezoelectric transformer, ultrasonic motor, actuator, ultrasonic vibrator, etc. Seen from this viewpoint, it is possible to produce a piezoelectric transformer, ultrasonic motor, actuator, ultrasonic vibrator, etc. having a higher electromechanical energy conversion efficiency the higher the electromechanical coupling coefficient Kp of the piezoelectric ceramic composition. Further, to fabricate a piezoelectric transformer, ultrasonic motor, actuator, ultrasonic vibrator, etc. having properties equal to or better than the comparison Sample C1, it can be said to be preferable to have an electromechanical coupling coefficient Kp of at least 0.3. More preferably, it should be at least 0.34. Still more preferably, it should be at least 0.4. Most preferably, it should be at least 0.45.

Taking note of the mechanical quality factor Qm, as will be understood from Table 20, the mechanical quality factor Qm of Sample D5 exhibited the highest value of 136.5.

Taking note of the Curie temperature Tc, the Curie temperatures TC of Samples D1 to D5 are all high values of at least 200° C. Therefore, the piezoelectric ceramic compositions of the present examples (Samples D1 to D5) can be utilized as knock sensors or other high temperature sensors, actuators, ultrasonic motors, etc. able to be used stably over a long period at high temperature locations such as near an automobile engine.

For further long-term stable use as a high temperature sensor, actuator, ultrasonic motor, etc., the Curie temperature Tc is preferably at least 200° C. More preferably it should be at least 250° C.

Taking note of the piezoelectric g₃₁constant, as will be understood from Table 20, the piezoelectric g₃₁constant of Sample D2 exhibits its highest value at 8.63×10⁻³Vm/N.

The piezoelectric g₃₁constant, like the piezoelectric d₃₁constant, is proportional to the output voltage of a piezoelectric sensor, piezoelectric element, ultrasonic motor, etc. Therefore, it is possible to produce a sensor with a larger voltage sensor output the higher the piezoelectric g₃₁constant of the piezoelectric ceramic composition. Further, to fabricate a sensor having properties equal to or better than the comparison, it can be said to be preferable to have a piezoelectric g₃₁constant of at least 7×10⁻³Vm/N. More preferably, it should be at least 8×10⁻³Vm/N.

Taking note of the relative dielectric constant ∈_33τ/∈₀, the relative dielectric constants ∈_33τ/∈₀of the Samples D1 to D5 are extremely high values of at least 1000.

Taking note of the dielectric loss tan δ, the dielectric losses tan δ of the Samples D1 to D5 are extremely low values of not more than 0.22.

As explained above, the piezoelectric ceramic compositions (Sample D1 to Sample D5) of the present examples are of compositions not containing lead and have superior piezoelectric properties and dielectric properties. Therefore, they are safe to the environment and can be utilized for high performance piezoelectric elements and dielectric elements.

Further, the piezoelectric ceramic compositions of these examples, as explained above, are particularly superior in the mechanical quality factor Qm. Therefore, the piezoelectric ceramic compositions are particularly suitable for piezoelectric actuators, ultrasonic motors, piezoelectric transformers, piezoelectric vibrators, etc. with little heat generation.

EXAMPLE GROUP V

These examples are of compounds of the above general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃containing different amounts of NiO as additives in order to determine the critical range of content of the additive.

First, as the materials of the piezoelectric ceramic composition, over 99% purity high purity Li₂CO₃, Na₂CO₃, K₂CO₃, Nb₂O₅, Ta₂O₅, and Sb₂O₅and, as the additive, NiO were prepared.

Among these materials, the Li₂CO₃, Na₂CO₃, K₂CO₃, Nb₂O₅, Ta₂O₅, and Sb₂O₅were mixed by a stoichiometric ratio giving a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are x=0.04, y=0.5, z=0.1, and w=0.06, then the NiO serving as the additive was mixed in different amounts to obtain five types of formulations.

Regarding the amounts of incorporation of the NiO, the NiO of the additive was included in amounts of 0.001 mol to 0.08 mol with respect to 1 mol of the compound {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04)O₃expected to be obtained by formulation by the above stoichiometric ratio. At this time, the amount of Ni of the added element was 0.001 to 0.08 mol.

The formulations were kneaded by ball mills in acetone for 24 hours to fabricate mixtures.

Next, in the same way as Sample D1 to Sample D5 of the Example Group IV, the mixtures were calcined, granulated, shaped, sintered, and polarized to prepare five types of piezoelectric ceramic compositions. These were used as Sample G1 to Sample G5. The ratios of the materials and additive in the samples are shown in Table 21.

In these examples, to clarify the effects of the incorporation of Ni, samples were prepared by external addition to main ingredients compounds.

Further, in Samples G1 to G5 obtained here, the NiO of the additive may be contained in the grains or at the grain boundaries of the piezoelectric ceramic compositions in part in its inherent form or in the form of compounds such as perovskite structure compounds with at least one of the basic composition elements lithium, sodium, potassium, niobium, tantalum, and antimony and may be contained in part in a state with the nickel in the NiO substituting at least part of the lithium, potassium, and sodium of the {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04)O₂. In particular, when the amount added of the Ni as the added element included in the additive NiO exceeds 2 mol with respect to 1 mol of the compound of the above {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04)O₃, the NiO of the additive easily precipitates in the form of nickel and or NiO or a compound containing nickel at the grain boundaries of the piezoelectric ceramic compositions.

Next, in these examples, to clarify the effects of the incorporation of NiO, a sample not containing NiO as an additive was prepared.

Specifically, first, at least 99% purity high purity Li₂CO₃, Na₂CO₃, K₂CO₃, Nb₂O₅, Ta₂O₄, and Sb₂O₅were prepared. These materials were mixed by a stoichiometric ratio giving a compound of {Li_0.04(K_0.5Na_0.5)_0.96}(Nb0.84Ta_0.1Sb_0.04)O₃then mixed by a ball mill in acetone for 24 hours to obtain a mixture. This mixture was calcined, granulated, shaped, sintered, and polarized in the same way as in Samples D1 to D5 of the Example Group IV to obtain a piezoelectric ceramic composition (Sample P1). The composition of the Sample P1 is shown in Table 21.

TABLE 21

Added

Additive
element

Composition ratio of

Am't

Am't

sample

added

added

Sample no.
x
y
z
w
Comp.
(mol)
Type
(mol)

Sample G1
0.04
0.5
0.1
0.4
NiO
0.001
Ni
0.001

Sample G2
0.04
0.5
0.1
0.4
NiO
0.01
Ni
0.01

Sample G3
0.04
0.5
0.1
0.4
NiO
0.02
Ni
0.02

Sample G4
0.04
0.5
0.1
0.4
NiO
0.04
Ni
0.04

Sample G5
0.04
0.5
0.1
0.4
NiO
0.08
Ni
0.08

Sample P1
0.04
0.5
0.1
0.4
—
0
—
0

Next, the Samples G1 to G5 and Sample P1 were measured for the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, mechanical quality factor Qm, relative dielectric constant ∈_33τ/∈₀, dielectric loss tan δ, and Curie temperature Tc in the same way as in Example Group I. The results are shown in Table 22. Note that Table 22 also shows the results of Sample C1 prepared in Example Group IV for comparison.

TABLE 22

g₃₁

d₃₁

(× 10⁻³

Tc

(pm/V)
Kp
Vm/N)
Qm
ε_33τ/ε₀
tanδ
(° C.)

Sample G1
97.2
0.487
7.91
65.2
1392.3
0.022
309

Sample G2
98.8
0.489
8.42
78.8
1266.5
0.021
312

Sample G3
100.5
0.489
8.11
75.3
1399.5
0.019
319

Sample G4
97.6
0.472
7.73
78.4
1411.5
0.020
322

Sample G5
94.7
0.462
7.65
93.3
1398.5
0.019
325

Sample C1
37.6
0.334
9.9
100.6
429
0.036
415

Sample P1
96.1
0.452
7.81
48.4
1389.3
0.026
308

As will be understood from Table 22, the Samples G1 to G5 had a superior piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, mechanical quality factor Qm, relative dielectric constant ∈_33τ/∈₀, dielectric loss tan δ, and Curie temperature Tc equal or better than the Sample C1 and Sample P1. In particular, the mechanical quality factor Qm was greatly improved in each of the Samples G1 to G5 compared with the Sample P1 not containing NiO as an additive.

As will be understood from Table 21 and Table 22, when the amount of the NiO added as an additive is 0.001 mol to 0.08 mol in content of the added element nickel with respect to 1 mol of the compound of the above general formula, the piezoelectric ceramic composition is particularly superior in the piezoelectric properties and dielectric properties. Note that while not shown in the tables, the same effects as in these examples were obtained for the other metal elements as well.

EXAMPLE GROUP VI

Next, the piezoelectric ceramic compositions of Example Group VI will be explained. In these examples, the above piezoelectric ceramic compositions were produced and measured in physical properties. The piezoelectric ceramic compositions of these examples were piezoelectric ceramic compositions containing as main ingredients compounds of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2. The piezoelectric ceramic compositions included added elements of at least one metal element selected from silver, aluminum, gold, boron, barium, bismuth, calcium, cerium, cobalt, cesium, copper, dysprosium, erbium, europium, iron, gallium, gadolinium, germanium, hafnium, holmium, indium, iridium, lanthanum, lutetium, magnesium, manganese, neodymium, nickel, palladium, praseodymium, platinum, rubidium, rhenium, ruthenium, scandium, silicon, samarium, tin, strontium, terbium, titanium, thulium, vanadium, yttrium, ytterbium, zinc, and zirconium. Further, the total of the contents of the added elements was 0.01 mol with respect to 1 mol of the compound of the above general formula. Further, the open porosity of the piezoelectric ceramic compositions was not more than 0.4 vol %.

The method of production of the piezoelectric ceramic compositions of these examples comprises mixing a compound containing lithium, a compound containing sodium, a compound containing potassium, a compound containing niobium, a compound containing tantalum, and a compound containing antimony by a stoichiometric ratio giving, after sintering, a compound of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2, mixing an additive containing at least one metal element selected from silver, aluminum, gold, boron, barium, bismuth, calcium, cerium, cobalt, cesium, copper, dysprosium, erbium, europium, iron, gallium, gadolinium, germanium, hafnium, holmium, indium, iridium, lanthanum, lutetium, magnesium, manganese, neodymium, nickel, palladium, praseodymium, platinum, rubidium, rhenium, ruthenium, scandium, silicon, samarium, tin, strontium, terbium, titanium, thulium, vanadium, yttrium, ytterbium, zinc, and zirconium, and sintering the result.

Next, the method of production of the piezoelectric ceramic compositions of these examples will be explained in more detail.

First, as the materials of the piezoelectric ceramic compositions, over 99% purity high purity Li₂CO₃, Na₂CO₃, K₂CO₃, Nb₂O₅, Ta₂O₅, and Sb₂O₅ZnO were prepared.

Next, these materials and at least one compound of Ag₂O, Al₂O₃, Au, Au₂O₃, B₂O₃, H₃BO₃, BaO, BaO₂, BaCO₃, Bi₂O₃, CaO, CaCO₃, CeO₂, Ce₂(CO₃)₃, CoO, Co₃O₄, CoCo₃, Cs₂CO₃, CuO, Cu₂O, Dy₂O₂, Er₂O₃, Eu₂O₃, Fe₂O₃, Ga₂O₃, Gd₂O₃, GeO₂, HfO₂, Ho₂O₃, In₂O₃, IrO₂, Ir₂O₃, La₂O₃, Lu₂O₃, MgO, MgC₂O₄, MnO, MnO₂, Mn₂O₃, Mn₃O₄, Nd₂O₃, Nd₂CO₃, NiO, NiCO₃, PdO, Pr₂O₃, Pr₆O₁₁, Pr₂(CO₃)₃), PtO₂, Rb₂O, Rb₂CO₃, Re₂O₇, RuO₂, Sc₂O₃, SiO₂, SiO, SiC, Sm₂O₃, SnO, SnO₂, SrO, SrCO₃, Tb₄O₇, TiO, Ti₂O₃, TiO₂, Tm₂O₃, V₂O₃, V₂O₄, V₂O₅, Y₂O₃, Y₂(CO₃)₃, Yb₂O₃, ZnO, and ZrO₂were mixed by compositions of the compound {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04))O₃containing the metal elements included in the above additives in the piezoelectric ceramic compositions to obtain 47 types of formulations. The elements added may be present in the crystal grains of the piezoelectric ceramic compositions or at the crystal grain boundaries.

Regarding the amounts of incorporation of these additives, the the additives were included in the amounts shown in Table 23 and Table 24 with respect to 1 mol of the compound {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04))O₃expected to be obtained by formulation by the above stoichiometric ratio and sintering. At this time, the contents of the additives were set so that the amounts of the metal elements included in the additives became 0.01 mol no matter which of the additives included in.

The formulations were mixed by ball mills in acetone for 24 hours to fabricate mixtures.

In this way, 47 types of piezoelectric ceramic compositions (Samples H1 to H47) were prepared. The ratios of the materials and additives in the samples are shown in Table 23 and Table 24.

Note that as a method different from the method of production of these examples, it is also possible to fabricate piezoelectric ceramic compositions similar to the Samples H1 to H47 by fabricating a compound of the above {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04)O₃by sintering, pulverizing this, mixing the result with the above additives, then calcining, granulating, shaping, and sintering the results in the same way as the method of production of the present examples.

Next, in these examples, to clarify the superior properties of the piezoelectric ceramic compositions (Samples H1 to H47), three types of comparisons (Sample Q1 to Sample Q3) were fabricated as follows:

First, as materials of the comparisons, at least 99% purity high purity Li₂CO₃, Na₂CO₃, K₂CO₃, Nb₂O₅, Ta₂O₅, Sb₂O₅, MoO₃, and WO₃were prepared. Among these materials, the Li₂CO₃, Na₂CO₃, K₂CO₃, Nb₂O₅, Ta₂O₅, and Sb₂O₅were mixed by a stoichiometric ratio giving the general formula {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04)O₃to obtain a formulation.

The formulation was mixed by a ball mill in acetone for 24 hours, then, in the same way as Samples H1 to H47, was calcined, granulated, shaped, sintered, and polarized to obtain a piezoelectric ceramic composition for comparison (Sample Q1). This Sample Q1 was a piezoelectric ceramic composition not containing any of the above added elements.

Further, formulations obtained by mixing the ingredients by a stoichiometric ratio to give the above {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04)O₃had MoO₃or WO₃added to them as additives to prepare two types of formulations. The amounts of the additives added at that time were as shown in Table 24.

Next, these formulations were mixed by ball mills in acetone for 24 hours, then, in the same way as Samples H1 to H47, were calcined, granulated, shaped, sintered, and polarized to obtain piezoelectric ceramic compositions for comparison (Sample Q2 and Sample Q3). The Sample Q2 and Sample Q3 were compounds containing 0.01 mol of the MoO₃and WO₃in terms of metal elements with respect to 1 mol of the {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04)O₃.

Next, the apparent densities and the open porosities of the Samples H1 to H47 and the Samples Q1 to Q3 were measured. The results are shown in Table 23 and Table 24.

Note that the open porosity was measured by the following method:

(Open Porosity)

First, the weight of the sample was measured and this figure used as the dry weight. Next, the sample was completely immersed in water, bubbles were removed by vacuum, and the sample was made to sufficiently absorb water. The sample was weighed in the state with the sample immersed In water by the Archimedes method and this figure used as the weight in water. Next, the sample was pulled out from the water, the excess water was removed, then the weight of the sample was again measured. This figure was used as the weight containing water.

Next, the open porosity (vol %) of the sample was calculated from the thus obtained dry weight, weight in water, and weight containing water using the following equation (1):

Open porosity (vol %)=(weight containing water−dry weight)/(weight containing water−weight in water) (1)

TABLE 23

Apparent

Additive

density ρ
Open

Am't
Added element
after
porosity

added

Content
sintering
Pop

Comp.
(mol)
Type
(mol)
(g/cm3)
(vol %)

Sample H1
Ag₂O
0.005
Ag
0.01
4.752
0.077

Sample H2
Al₂O₃
0.005
Al
0.01
4.729
0.380

Sample H3
Au
0.01
Au
0.01
4.587
0.000

Sample H4
B₂O₃
0.005
B
0.01
4.719
0.076

Sample H5
BaO
0.01
Ba
0.01
4.730
0.076

Sample H6
Bi₂O₃
0.005
Bi
0.01
4.799
0.231

Sample H7
CaO
0.01
Ca
0.01
4.680
0.075

Sample H8
CeO₂
0.005
Ce
0.01
4.767
0.385

Sample H9
CoO
0.01
Co
0.01
4.750
0.078

Sample H10
Cs₂CO₃
0.005
Cs
0.01
7.726
0.384

Sample H11
CuO
0.01
Cu
0.01
4.722
0.076

Sample H12
Dy₂O₃
0.005
Dy
0.01
4.770
0.000

Sample H13
Er₂O₃
0.005
Er
0.01
4.767
0.000

Sample H14
Eu₂O₃
0.005
Eu
0.01
4.747
0.230

Sample H15
Fe₂O₃
0.005
Fe
0.01
4.774
0.156

Sample H16
Ga₂O₄
0.005
Ga
0.01
4.721
0.076

Sample H17
Gd₂O₃
0.005
Gd
0.01
4.773
0.077

Sample H18
GeO₂
0.01
Ge
0.01
4.705
0.151

Sample H19
HfO₂
0.01
Hf
0.01
4.757
0.077

Sample H20
Ho₂O₃
0.005
Ho
0.01
4.776
0.077

Sample H21
In₂O₃
0.005
In
0.01
4.710
0.000

Sample H22
IrO₂
0.01
Ir
0.01
4.757
0.248

Sample H23
La₂O₃
0.005
La
0.01
4.766
0.380

Sample H24
Lu₂O₃
0.005
Lu
0.01
4.751
0.000

Sample H25
MgO
0.01
Mg
0.01
4.731
0.378

Sample H26
MnO
0.01
Mn
0.01
4.729
0.153

Sample H27
Nd₂O₃
0.005
Nd
0.01
4.749
0.154

Sample H28
NiO
0.01
Ni
0.01
4.737
0.077

TABLE 24

Apparent

Additive

density ρ
Open

Am't
Added element
after
porosity

added

Content
sintering
Pop

Comp.
(mol)
Type
(mol)
(g/cm3)
(vol %)

Sample H29
PdO
0.01
Pd
0.01
4.720
0.077

Sample H30
Pr₂O₃
0.005
Pr
0.01
4.805
0.078

Sample H31
PtO₂
0.01
Pt
0.01
4.774
0.166

Sample H32
Rb₂O
0.005
Rb
0.01
4.730
0.000

Sample H33
Re₂O₇
0.005
Re
0.01
4.664
0.152

Sample H34
RuO₂
0.01
Ru
0.01
4.758
0.153

Sample H35
Sc₂O₃
0.005
Sc
0.01
4.731
0.076

Sample H36
SiO₂
0.01
Si
0.01
4.721
0.000

Sample H37
Sm₂O₃
0.005
Sm
0.01
4.709
0.000

Sample H38
SnO₂
0.01
Sn
0.01
4.741
0.000

Sample H39
SrCO₃
0.01
Sr
0.01
4.501
1.004

Sample H40
Tb₄O₇
0.0025
Tb
0.01
4.752
0.000

Sample H41
TiO₂
0.01
Ti
0.01
4.691
0.000

Sample H42
Tm₂O₃
0.005
Tm
0.01
4.778
0.077

Sample H43
V₂O₂
0.01
V
0.01
4.696
0.000

Sample H44
Y₂O₃
0.005
Y
0.01
4.767
0.000

Sample H45
Yb₂O₃
0.005
Yb
0.01
4.769
0.155

Sample H46
ZnO
0.01
Zn
0.01
4.751
0.308

Sample H47
ZrO₂
0.01
Zr
0.01
4.744
0.076

Sample Q1
—
—
—
—
4.617
0.408

Sample Q2
MoO₃
0.01
Mo
0.01
4.458
4.969

Sample Q3
WO₃
0.01
W
0.01
4.500
3.258

As will be understood from Table 23 and Table 24, the piezoelectric ceramic compositions of Samples H1 to H47 exhibited equal or higher apparent densities compared with Sample Q1 to Sample Q3 provided as comparisons and exhibited low values of open porosities of not more than 0.4 vol %.

In this way, it is learned that the piezoelectric ceramic compositions of Samples H1 to H47 are superior in mechanical strength.

Further, while not shown in Table 23 and Table 24, the piezoelectric properties and dielectric properties of the Samples H1 to H47 were measured by the resonance-antiresonance method using an impedance analyzer, whereupon it was found that the piezoelectric ceramic compositions of Samples H1 to H47 were superior in the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, mechanical quality factor Qm, relative dielectric constant, dielectric loss, Curie temperature, and other piezoelectric properties and dielectric properties.

Therefore, the piezoelectric ceramic compositions of these examples are superior in mechanical strength and can be utilizes as high performance piezoelectric elements and dielectric elements.

EXAMPLE GROUP VII

In these examples, samples of the general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃(where 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, 0<w≦0.2) containing additives in a state with at least part of the lithium, potassium, sodium, niobium, tantalum, and antimony substituted by the metal elements in the additives (hereinafter called “suitably substituted samples”) and samples containing the additives by external addition (hereinafter called “suitably externally added samples”) were prepared and their properties were compared.

First, as the externally added samples, the Sample H1, Sample H5, Sample H7, Sample H10, Sample H25, Sample H32, and Sample H39 prepared in Example Group VI were prepared. These Sample H1, Sample H5, Sample H7, Sample H10, Sample H25, Sample H32, and Sample H39 were obtained by externally adding to the compound {Li_0.4(K_0.5Na_0.5)_0.96}Nb_0.86Ta_0.1Sb_0.04)O₃as additives, Ag₂O, BaO, CaCO₃, Cs₂CO₂, MgO, Rb₂O, or SrCO₃.

Next, the samples with the above additives added by substitution were prepared in the following way.

First, as the materials of the basic composition of the piezoelectric ceramic compositions, at least 99% purity high purity Li₂CO₃, Na₂CO₃, K₂CO₃, Nb₂O₅, Ta₂O₅, Sb₂O₅, and the above additives Ag₂O, BaO, CaCO₃, Cs₂CO₃, MgO, Rb₂O, or SrCO₃were prepared.

Next, the materials of the basic composition and one type of the above additive were blended by a stoichiometric ratio giving the compound {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04)O₃in which the metal element in the additive is present in solid solution by substitution after sintering to thereby prepare seven types of formulations. Specifically, these became {Li_0.04(K_0.5Na_0.5)_0.95Ag_0.01}(Nb_0.86Ta_0.1Sb_0.04)O₃, {Li_0.04(K_0.5Na_0.5)_0.94Ba_0.01}(Nb_0.86Ta_0.1Sb_0.04)O₃, {Li_0.04(K_0.5Na_0.5)_0.94Ca_0.01}(Nb_0.86Ta_0.1Sb_0.04)O₃, {Li_0.04(K_0.5Na_0.5)_0.95Cs_0.02}(Nb_0.86Ta_0.1Sb_0.04)O₃, {Li_0.04(K_0.5Na_0.5)_0.95Mg_0.01}(Nb_0.86Ta_0.1Sb_0.04)O₃, {Li_0.04(K_0.5Na_0.5)_0.95Rb_0.01}(Nb_0.86Ta_0.1Sb_0.04)O₃, and {Li_0.04(K_0.5Na_0.5)_0.94Sr_0.01}(Nb_0.86Ta_0.1Sb_0.04)O₃.

Next, these formulations were mixed by ball mills in acetone for 24 hours to obtain mixtures.

Next, these mixtures were calcined, granulated, shaped, sintered, and polarized in the same way as Samples H1 to H47 of the Example Group VI.

In this way, piezoelectric ceramic compositions having the additives Ag₂O, BaO, CaCO₃, Cs₂CO₃, MgO, Rb₂O, and SrCO₃added by substitution were prepared. These were used as the Samples H1a, H5a, H7a, H10a, H25a, H32a, and H39a.

Sample H1 and Sample H1a, Sample H5 and Sample H5a, Sample H7 and Sample H7a, Sample H10 and Sample H10a, Sample H25 and Sample H25a, and Sample H32 and Sample H32a were piezoelectric ceramic compositions containing additives including the same metal elements with—the former being samples obtained by external addition and the latter being samples obtained by substitution.

Next, the samples were measured for apparent density and open porosity. The results are shown in Table 25. Table 25 also shows the apparent density and open porosity of the Sample Q1 prepared in Example Group VI for comparison.

TABLE 25

Apparent

density ρ after
Open

Added
sintering
porosity

Additive
element
(g/cm3)
Pop (vol %)

Sample H1
Ag₂O
Ag
4.752
0.077

Sample H1a
Ag₂O
Ag
4.748
0.075

Sample H5
BaO
Ba
4.730
0.076

Sample H5a
BaO
Ba
4.752
0.075

Sample H7
CaCO₃
Ca
4.680
0.075

Sample H7a
CaCO₃
Ca
4.704
0.081

Sample H10
Cs₂CO₃
Cs
4.726
0.384

Sample H10a
Cs₂CO₃
Cs
4.725
0.082

Sample H25
MgO
Mg
4.731
0.378

Sample H25a
MgO
Mg
4.731
0.081

Sample H32
Rb₂O
Rb
4.730
0.000

Sample H32a
Rb₂O
Rb
4.729
0.243

Sample H39
Sr₂CO₃
Sr
4.501
1.004

Sample H39a
Sr₂CO₃
Sr
4.729
0.163

Sample Q1
—
—
4.617
0.408

As will be understood from Table 25, Sample H1 and Sample H1a, Sample H5 and Sample H5a, Sample H7 and Sample H7a, Sample H10 and Sample H10a, Sample H25 and Sample H25a, and Sample H32 and Sample H32a exhibited apparent densities equal to or better than Sample Q1 and open porosities lower than Sample Q1.

From this, it is understood that the piezoelectric ceramic compositions of these examples are superior in apparent density and open porosity both when the additives are incorporated by external addition and incorporated by substitution.

Further, in the case of the Sample H41 and Sample H41a containing strontium, a high apparent density and low open porosity were obtained in the Sample H41a of the substitution composition.

EXAMPLE GROUP VIII

These examples are examples of piezoelectric ceramic compositions containing different amounts of an additive. First, as the materials of the basic composition of the piezoelectric ceramic compositions, over 99% purity high purity Li₂CO₃, Na₂CO₃, K₂CO₃, Nb₂O₅, Ta₂O₅, and Sb₂O₅and, as the additive, Bi₂O₃were prepared.

Among these materials, the Li₂CO₃, Na₂CO₃, K₂CO₃, Nb₂O₅, Ta₂O₅, and Sb₂O₅were mixed by a stoichiometric ratio giving a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are x=0.04, y=0.5, z=0.1, and w=0.06, then the Bi₂O₃serving as the additive was mixed in different amounts to obtain formulations.

The additive Bi₂O₃was added in amounts of 0.0025, 0.0005, and 0.00025 mol with respect to 1 mol of the compound {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04)O₃expected to be obtained by formulation by the above stoichiometric ratio. That is, the metal element (bismuth) in the additive was included in amounts of 0.005, 0.001, and 0.0005 mol.

The formulations were mixed by ball mills in acetone for 24 hours to fabricate mixtures.

Next, in the same way as Sample H1 to Sample H47, the mixtures were calcined, granulated, shaped, sintered, and polarized to prepare three types of piezoelectric ceramic compositions (Sample H6x, Sample H6y, and Sample H6z). The types and amounts of the additive in the samples are shown in Table 26.

Next, the apparent densities and open porosities of the Sample H6x, Sample H6y, and Sample H6z were measured by the same method as in Example Group VI. The results are shown in Table 26.

Note that in Table 26, for comparison, the results of a Sample H6 prepared by the Example Group VI containing 0.01 mol of bismuth as the added element and a Sample Q1 not containing an added element are also shown.

TABLE 26

Apparent

Additive

density ρ
Open

Am't
Added element
after
porosity

added

Content
sintering
Pop

Comp.
(mol)
Type
(mol)
(g/cm3)
(vol %)

Sample H6
Bi₂O₃
0.005
Bi
0.01
4.799
0.231

Sample H6x
Bi₂O₃
0.0025
Bi
0.005
4.734
0.163

Sample H6y
Bi₂O₃
0.0005
Bi
0.001
4.738
0.164

Sample H6z
Bi₂O₃
0.00025
Bi
0.0005
4.757
0.246

Sample Q1
—

—
—
4.617
0.408

As will be understood from Table 26, the Sample H6, Sample H6x, Sample H6y, and Sample H6z exhibited higher apparent densities and lower open porosities compared with the Sample Q1. That is, in the piezoelectric ceramic compositions of these examples, by including the above additive in the amounts of 0.0005 mol to 0.01 mol in terms of content of the metal element in the additive with respect to 1 mol of the compound {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.5Sb_0.04)O₃, it is possible to improve the apparent density and open porosity of the piezoelectric ceramic compositions.

Further, in general, if the open porosity is large, the porosity becomes larger. Therefore, by adding the additive as in the present examples, the ability to reduce the open porosity can be said to reduce the porosity as well.

EXAMPLE GROUP IX

Next, piezoelectric ceramic compositions of Example Group IX will be explained. In these examples, piezoelectric ceramic compositions were produced and measured in physical properties. The piezoelectric ceramic compositions of these examples were piezoelectric ceramic compositions containing as main ingredients compounds of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦_0.2. The piezoelectric ceramic compositions included added elements of at least one metal element selected from magnesium, calcium, strontium, and barium. Further, the total of the contents of the added elements was 0.01 mol with respect to 1 mol of the compound of the above general formula.

The above additive may be added to the above piezoelectric ceramic composition having the general formula by substitutional addition or external addition.

Next, the method of production of the piezoelectric ceramic compositions of these examples will be explained in more detail.

First, as the materials of the basic composition of the piezoelectric ceramic compositions, over 99% purity high purity Li₂CO₃, Na₂CO₃, K₂CO₃, Nb₂O₅, Ta₂O₅, and Sb₂O₅and, as the additive, CaO, SrO, MgO, and BaO were prepared.

Among these materials, the Li₂CO₃, Na₂CO₃, K₂CO₃, Nb₂O₅, Ta₂O₅, and Sb₂O₅were mixed by a stoichiometric ratio giving a general formula {Li_x(L_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are x=0.04, y=0.5, z=0.1, and w=0.04, that is, a stoichiometric ratio whereby the general formula becomes

{Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04))O₃, then the CaO, SrO, MgO, and BaO serving as the additives were mixed to obtain eight types of formulations.

Regarding the amounts of incorporation of these additives, the CaO, SrO, MgO, and BaO of the additives were included in amounts of 0.01 mol and 0.005 mol each with respect to 1 mol of the compound {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04))O₃expected to be obtained by formulation by the above stoichiometric ratio. At this time, the amounts of the metal elements of the additives also became 0.01 mol and 0.005 mol.

Further, the CaO was also included 0.02 mol, 0.04 mol and 0.10 mol.

The formulations were kneaded by ball mills in acetone for 24 hours to fabricate mixtures.

In this way, eight types of piezoelectric ceramic compositions (Samples J1 to J4. Samples F1 to F4 and Samples L1 to L3) were prepared. The ratios of the materials and additives in the samples are shown in Table 27.

These examples were prepared by substitutional addition that part of (K_0.5Na_0.5) is substituted by the metal element in the additives. For example, sample J1 had a composition of {Li_0.04(K_0.5Na_0.5)_0.94Ca_0.01}(Nb_0.86Ta_0.1Sb_0.04)O₃.

Note that as a method different from the method of production of these examples, it is also possible to fabricate piezoelectric ceramic compositions similar to the Samples J1 to J4, Samples F1 to F4, and Samples L1 to L3 by fabricating a compound of the above pulverizing this, mixing the result with the above additives, then calcining, granulating, shaping, and Sintering the results in the same way as the method of production of the present examples.

Further, in Samples J1 to J4, Samples F1 to F4 and Samples L1 to L3 of these examples, the CaO, SrO, MgO, and BaO of the additives may be contained in the grains or at the grain boundaries of the piezoelectric ceramic compositions in part as oxides or perovskite structure compounds or other compounds and may be contained in part in a state with the calcium, strontium, magnesium, and barium atoms substituting at least part of the lithium, potassium, and sodium of the compound of the above {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04)O₃.

Among these materials, the K₂CO₃, Na CO₃, and Nb₂O₅were mixed by a stoichiometric ratio giving the above general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃wherein x=z=w=0 and y=0.5, that is, a stoichiometric ratio giving the above general formula (K_0.5Na_0.5)NbO₃, then mixed by a ball mill in acetone for 24 hours to obtain a mixture This mixture was calcined, granulated, shaped, sintered, and polarized in the same way as in Samples J3 to J4, Samples F1 to F4 and Samples L1 to L3 to obtain a piezoelectric ceramic composition as a comparison (Sample C1). The Sample C1 was a piezoelectric ceramic composition containing (K_0.5Na_0.5)NbO₃.

Next, the Sample C2 was fabricated as follows: First, the Li₂CO₃, Na₂CO₃, K₂CO₃, Nb₂O₅, Ta₂O₅, and Sb₂O₅of the above prepared materials were mixed by a stoichiometric ratio giving the above general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃wherein x=0.04, y=0.5, z=0.1, and w=0.04 after sintering, that is, a stoichiometric ratio giving the above general formula {Li_0.04(K_0.5Na_0.5)_0.96}Nb_0.86Ta_0.1Sb_0.04)O₃, then mixed by a ball mill in acetone for 24 hours to obtain a mixture. This mixture was calcined, granulated, shaped, sintered, and polarized in the same way as in Samples J1 to J4, Samples F1 to F4, and Samples L1 to L3 to obtain a piezoelectric ceramic composition as a comparison (Sample C2). The Sample C2, in the same way as the Samples J1 to J4, Samples F1 to F4, and Samples L1 to L3, was a piezoelectric ceramic composition which contained {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04)O₃as a main ingredient, but did not contain the above added elements.

The compositions of the Sample C1 and Sample C2 are shown in Table 27.

TABLE 27

Added

Additive
element

Composition ratio of

Am't

Am't

sample

added

added

x
y
z
w
Comp.
(mol)
Type
(mol)

Sample J1
0.04
0.5
0.1
0.4
CaO
0.01
Ca
0.01

Sample J2
0.04
0.5
0.1
0.4
SrO
0.01
Sr
0.01

Sample J3
0.04
0.5
0.1
0.4
MgO
0.01
Mg
0.01

Sample J4
0.04
0.5
0.1
0.4
BaO
0.01
Ba
0.01

Sample F1
0.04
0.5
0.1
0.4
CaO
0.005
Ca
0.005

Sample F2
0.04
0.5
0.1
0.4
SrO
0.005
Sr
0.005

Sample F3
0.04
0.5
0.1
0.4
MgO
0.005
Mg
0.005

Sample F4
0.04
0.5
0.1
0.4
BaO
0.005
Ba
0.005

Sample L1
0.04
0.5
0.1
0.04
CaO
0.02
Ca
0.02

Sample L2
0.04
0.5
0.1
0.04
CaO
0.04
Ca
0.04

Sample L3
0.04
0.5
0.1
0.04
CaO
0.1
Ca
0.1

Sample C1
0
0.5
0
0
—
—
—
0

Sample C2
0.04
0.5
0.1
0.4
—
—
—
0

Next, the Samples J1 to J4, Samples F1 to F4, Samples L1 to L3, and Samples C1 and C2 were measured for the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, mechanical quality factor Qm, relative dielectric constant ∈_33τ/∈₀, dielectric loss tan δ, and Curie temperature Tc. The piezoelectric d₃₁constant, piezoelectric g₃₁constant, electromechanical coupling coefficient Kp, and mechanical quality factor Qm were measured by the resonance-antiresonance method using an impedance analyzer (Precision Impedance Analyzer 4294A made by Agilent Co.) The dielectric loss tan δ and relative dielectric constant ∈_33τ/∈₀were measured at a measurement frequency of 1 kHz using an impedance analyzer the same as the above. For the Curie temperature Tc, the temperature giving the highest relative dielectric constant ∈_33τ/∈₀was made the Curie temperature Tc. The results are shown in Table 28.

TABLE 28

g₃₁

d₃₁

(× 10⁻³

Tc

(pm/V)
Kp
Vm/N)
Qm
ε_33τ/ε₀
tanδ
(° C.)

Sample J1
106.3
0.484
7.63
41.8
1573.7
0.020
284

Sample J2
102.1
0.480
7.57
38.3
1522.9
0.034
292

Sample J3
97.9
0.467
8.11
59.4
1363.6
0.023
312

Sample J4
95.3
0.449
7.18
45.9
1498.5
0.027
295

Sample F1
110.6
0.500
7.86
49.1
1589.5
0.023
296

Sample F2
121.0
0.551
8.81
25.2
1550.5
0.030
300

Sample F3
85.9
0.432
7.30
47.9
1329.7
0.034
310

Sample F4
104.5
0.485
7.67
46.9
1538.9
0.022
302

Sample L1
102.0
0.468
7.62
65.2
1557.9
0.021
272

Sample L2
97.7
0.452
7.52
79.8
1542.1
0.019
260

Sample L3
70.2
0.436
7.42
75.3
1526.3
0.02
236

Sample C1
37.6
0.334
9.9
100.6
429
0.036
415

Sample C2
96.1
0.452
7.81
48.4
1389.3
0.026
308

As will be understood from Table 28, the Samples J1 to J4, Samples F1 to F4, and Samples L1 to L3 were improved over Sample C1 in the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, relative dielectric constant ∈_33τ/∈₀, and dielectric loss tan δ. Further, the Samples J1 to J4, Samples F1 to F4, and Samples L1 to L3 had equal or better properties even compared with the Sample C2 in at least one of the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, mechanical quality factor Qm, relative dielectric constant ∈_33τ/∈₀, dielectric loss tan δ, and Curie temperature Tc.

It was confirmed that the SrO, MgO, and BaO of the additives which were included in amounts of more than 0.01 mol (e.g. 0.10 mol) showed the same effect as that in CaO, while not shown in the present examples.

Here, taking note of the piezoelectric d₃₁constant, as will be understood from Table 28, the piezoelectric d₃₁constant of the Sample E2 exhibited the highest value of 121.0 pm/V.

- When using the composition as a charge detection type circuit or a current detection type circuit, in general the piezoelectric d₃₁constant is proportional to the output voltage of an accelerator sensor, weight sensor, impact sensor, knock sensor, and other piezoelectric type sensors. Seen from this point, it is possible to prepare a sensor with a charge sensor output larger the higher the piezoelectric d₃₁constant of the piezoelectric ceramic composition. Further, to fabricate a sensor having properties equal to or better than Sample C1, it can be said to be preferable to have a piezoelectric d₃₁constant of at least 30 pm/V. Further, to fabricate a high sensitivity sensor raised in the signal-to-noise ratio (SN ratio) and output voltage, the piezoelectric d₃₁constant should be at least 80 pm/V. More preferably it should be at least 100 pm/V.

Further, when using the composition as an actuator, in general the piezoelectric d₃₁constant is proportional to the generated distortion or displacement of the piezoelectric actuator. Seen from this point, it is possible to produce an actuator with a larger generated distortion or displacement the higher the piezoelectric d₃₁constant of the piezoelectric ceramic composition. Further, to fabricate an actuator having properties equal to or better than the comparison, it can be said preferable to have a piezoelectric d₃₁constant of at least 30 pm/V. More preferably it should be at least 40 pm/V. Further, to fabricate an actuator with a large displacement, the piezoelectric d₃₁constant should be at least 80 pm/V. More preferably, it should be at least 100 pm/V.

Further, taking note of the electromechanical coupling coefficient Kp, as will be understood from Table 28, the electromechanical coupling coefficient Kp of Sample F2 exhibits its highest value of 0.551.

In general, the electromechanical coupling coefficient Kp is proportional to the electromechanical energy conversion efficiency of the piezoelectric transformer, ultrasonic motor, actuator, ultrasonic vibrator, etc. Seen from this viewpoint, it is possible to produce a piezoelectric transformer, ultrasonic motor, actuator, ultrasonic vibrator, etc. having a higher electromechanical energy conversion efficiency the higher the electromechanical coupling coefficient Kp of the piezoelectric ceramic composition. Further, to fabricate a piezoelectric transformer, ultrasonic motor, actuator, ultrasonic vibrator, etc. having properties equal to or better than the comparison Sample C1, it can be said to be preferable to have an electromechanical coupling coefficient Kp of at least 0.3. More preferably, it should be at least 0.34. Still more preferably, it should be at least 0.4. Most preferably, it should be at least 0.45.

Taking note of the mechanical quality factor Qm, as will be understood from Table 28, the mechanical quality factors Qm of Samples J1 to J4 exhibited superior values equal to or better than the Sample C1 and Sample C2.

In general, the mechanical quality factor Qm, like the electromechanical coupling coefficient Kp, is proportional to the electromechanical energy conversion efficiency of the piezoelectric transformer, ultrasonic motor, actuator, ultrasonic vibrator, etc. Seen from this viewpoint, it is possible to produce a piezoelectric transformer, ultrasonic motor, actuator, ultrasonic vibrator, etc. having a higher electromechanical energy conversion efficiency the higher the mechanical quality factor Qm of the piezoelectric ceramic composition. Further, to fabricate a piezoelectric transformer, ultrasonic motor, actuator, ultrasonic vibrator, etc. having properties equal to or better than the comparison Sample C1, it can be said to be preferable to have a mechanical quality factor Qm of at least 50.

Taking note of the Curie temperature Tc, the Curie temperatures Tc of Samples J1 to J4 and Samples F1 to F4 are all high values of at least 200° C. Therefore, the piezoelectric ceramic compositions of the present examples (Samples J1 to J4 and Samples F1 to F4) can be utilized as knock sensors or other high temperature sensors, actuators, ultrasonic motors, etc. able to be used stably over a long period at high temperature locations such as near an automobile engine.

Taking note of the piezoelectric g₃₁constant, as will be understood from Table 28, the piezoelectric g₃₁constant of Sample F2 exhibits its highest value at 8.81×10⁻³Vm/N.

Taking note of the relative dielectric constant ∈_33τ/∈₀, the relative dielectric constants ∈_33τ/∈₀of the Samples J1 to J4 and Samples L1 to L3 are extremely high values of at least 1300.

The relative dielectric constant ∈_33τ/∈₀is generally proportional to the electrostatic capacity of a multilayer capacitor or other capacitor. Seen from this point, it is possible to produce a capacitor with a larger electrostatic capacity the higher the relative dielectric constant of the piezoelectric ceramic composition. To fabricate a capacitor, it can be said to be preferable to have a relative dielectric constant of at least 400. More preferably, it should be at least 430, Still more preferably, it should be at least 1000.

Taking note of the dielectric loss tan δ, the dielectric losses tan δ of the Samples J1 to J4 are extremely low values of not more than 0.034.

As explained above, the piezoelectric ceramic compositions (Sample J1 to Sample J4 and Sample F1 to Sample F4) of the present examples are of compositions not containing lead and have superior piezoelectric properties and dielectric properties. Therefore, they are safe to the environment and can be utilized for high performance piezoelectric elements and dielectric elements.

EXAMPLE GROUP X

Next, piezoelectric ceramic compositions of Example Group X will be explained. In these examples, piezoelectric ceramic compositions were produced and measured in physical properties. The piezoelectric ceramic compositions of these examples were piezoelectric ceramic compositions containing as main ingredients compounds of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2. The piezoelectric ceramic compositions included added elements of at least one metal element selected from silicon, indium, and scandium. Further, the total of the contents of the added elements was 0.01 mol with respect to 1 mol of the compound of the above general formula.

Next, the method of production of the piezoelectric ceramic compositions of these examples will be explained in more detail.

Among these materials, the Li₂CO₃, Na₂CO₃, K₂CO₃, Nb₂O₅, Ta₂O₅, and Sb₂O₅were mixed by a stoichiometric ratio giving a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are x=0.04, y=0.5, z=0.1, and w=0.04, that is, a stoichiometric ratio whereby the general formula becomes {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04))O₃, then the SiO₂, Sc₂O₃, and In₂O₃serving as the additives were mixed to obtain three types of formulations.

Regarding the amounts of incorporation of these additives, the SiO₂, ScO₃, and In₂O₃of the additives were included in amounts of 0.01 mol, 0.005 mol, and 0.005 mol with respect to 1 mol of the compound {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04))O₃expected to be obtained by formulation by the above stoichiometric ratio. That is, the amounts of the additives incorporated were set to give 0.01 mol amounts of the added elements silicon, scandium, and indium.

The formulations were kneaded by ball mills in acetone for 24 hours to fabricate mixtures.

Next, in the same way as Samples J1 to J4 of Example Group IX, the mixtures were calcined, granulated, shaped, sintered, and polarized to obtain three types of piezoelectric ceramic compositions (Sample J5 to J7). The ratios of the materials and additives in the samples are shown in Table 29.

Note that as a method different from the method of production of these examples, it is also possible to fabricate piezoelectric ceramic compositions similar to the Samples J5 to J7 by fabricating a compound of the above {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04)O₃by sintering, pulverizing this, mixing the result with the above additives, then calcining, granulating, shaping, and sintering the results in the same way as the method of production of the present examples.

Further, in Samples J5 to J7 of these examples, the SiO₂, Sc₂O₃, and In₂O₃of the additives may be contained at the grain boundaries of the piezoelectric ceramic compositions in part as oxides or perovskite structure compounds or other compounds and may be contained in part in a state with the silicon, scandium, and indium atoms substituting at least part of the niobium, tantalum, and antimony of the compound of the above {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04)O₃.

TABLE 27

Added

Additive
element

Composition ratio of

Am't

Am't

sample

added

added

x
y
z
w
Comp.
(mol)
Type
(mol)

Sample J5
0.04
0.5
0.1
0.4
SiO₂
0.01
Si
0.01

Sample J6
0.04
0.5
0.1
0.4
Sc₂O₃
0.005
Sc
0.01

Sample J7
0.04
0.5
0.1
0.4
In₂O₃
0.006
In
0.01

Next, in the same way as Example Group IX, the Samples J5 to J7 were measured for the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, pg₃₁c, mechanical quality factor Qm, relative dielectric constant ∈_33τ/∈₀, dielectric loss tan δ, and Curie temperature Tc.

The results are shown in Table 30. Note that Table 30 also shows, for comparison, the piezoelectric properties and dielectric properties of the Sample C1 and Sample C2 prepared in Example Group IX.

TABLE 30

d₃₁

g₃₁(×

ε_33τ/

Tc

(pm/V)
Kp
10⁻³Vm/N)
Qm
ε₀
tanδ
(° C.)

Sample J5
96.6
0.470
7.96
48.8
1370.3
0.024
304

Sample J6
101.9
0.489
7.95
50.4
1448.4
0.023
300

Sample J7
106.4
0.498
8.48
58.7
1416.5
0.020
311

Sample C1
37.5
0.334
9.9
100.6
429
0.036
415

Sample C2
96.1
0.452
7.81
48.4
1389.3
0.025
308

As well be understood from Table 30, the Samples J5 to J7 were remarkably improved over Sample C1 in the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, relative dielectric constant ∈_33τ/∈₀, and dielectric loss tan δ. Further, the Samples J5 to J7 were also improved over the Sample C2 in the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, mechanical quality factor Qm, and dielectric loss tan δ. The relative dielectric constant ∈_33τ/∈₀and the Curie temperature Tc were also equally or more superior.

It was confirmed that the additives which were included in amounts of 0.001-0.08 mol showed the same effect as shown in Table 30, while not shown in the present examples.

In this way, the piezoelectric ceramic compositions (Sample J5 to Sample J7) of the present examples are of compositions not containing lead and have superior piezoelectric properties and dielectric properties. Therefore, they are safe to the environment and can be utilized for high performance piezoelectric elements and dielectric elements.

EXAMPLE GROUP XI

Next, piezoelectric ceramic compositions of Example Group XI will be explained. In these examples, piezoelectric ceramic compositions were produced and measured in physical properties. The piezoelectric ceramic compositions of these examples were piezoelectric ceramic compositions containing as main ingredients compounds of a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w were in the ranges of 0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2. The piezoelectric ceramic compositions included bismuth as an added element. Further, the content of the added element was 0.0001 mol to 0.004 with respect to 1 mol of the compound of the above general formula.

Next, the method of production of the piezoelectric ceramic compositions of these examples will be explained in more detail.

Among these materials, the Li₂CO₃, Na₂CO₃, K₂CO₃, Nb₂O₅, Ta₂O₅, and Sb₂O₅were mixed by a stoichiometric ratio giving a general formula {Li_x(K_1-yNa_y)_1-x}(Nb_1-z-wTa_zSb_w)O₃where x, y, z, and w are x=0.04, y=0.5, z=0.1, and w=0.04, that is, a stoichiometric ratio whereby the general formula becomes {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04))O₃, then the Bi₂O₃serving as the additive was mixed in different amounts to obtain four types of formulations.

Regarding the amounts of incorporation of the additive, the Bi₂O₃of the additive was included in amounts of 0.00025 mol, 0.0005 mol, 0.0025 mol, and 0.005 mol with respect to 1 mol of the compound {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.96Ta_0.1Sb_0.04))O₃expected to be obtained by formulation by the above stoichiometric ratio. That is, the amounts of the additive incorporated were set to give 0.0005 mol, 0.001 mol, 0.005 mol, and 0.01 mol amounts of the bismuth.

The formulations were mixed by ball mills in acetone for 24 hours to fabricate mixtures.

Next, in the same way as Samples J1 to J4 and Samples F1 to F4 of Example Group IX, the mixtures were calcined, granulated, shaped, sintered, and polarized to obtain four types of piezoelectric ceramic compositions (Sample J8 to J11). The ratios of the materials and additives in the samples are shown in Table 31.

Note that as a method different from the method of production of these examples, it is also possible to fabricate piezoelectric ceramic compositions similar to the Samples J8 to J11 by fabricating a compound of the above {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04)O₃by sintering, pulverizing this, mixing the result with the above additives, then calcining, granulating, shaping, and sintering the results in the same way as the method of production of the present examples.

Further, in Samples J8 to J11 of these examples, the bismuth of the added element may be contained in the grains or at the grain boundaries of the piezoelectric ceramic compositions in part as oxides or perovskite structure compounds or other compounds and may be contained in part in a state with the bismuth atoms substituting at least part of the niobium, tantalum, and antimony of the compound of the above {Li_0.04(K_0.5Na_0.5)_0.96}(Nb_0.86Ta_0.1Sb_0.04)O₃.

TABLE 31

Composition ratio of Additive
Added

sample
element

Am't

Am't

added

added

x
y
z
w
Comp.
(mol)
Type
(mol)

Sample J8
0.04
0.5
0.1
0.4
Bi₂O₃
0.00025
Bi
0.0005

Sample J9
0.04
0.5
0.1
0.4
Bi₂O₄
0.005
Bi
0.001

Sample J10
0.04
0.5
0.1
0.4
Bi₂O₄
0.0025
Bi
0.005

Sample J11
0.04
0.5
0.1
0.4
Bi₂O₅
0.005
Bi
0.01

Next, in the same way as the Example Group IX, Samples J8 to J11 were measured for the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, piezoelectric g₃₁constant, mechanical quality factor Qm, relative dielectric constant ∈_33τ/∈₀, dielectric loss tan δ, and Curie temperature Tc. The results are shown in Table 32. note that Table 32 also shows for comparison the piezoelectric properties and dielectric properties of Sample C1 and Sample C2 prepared in Example Group IX.

TABLE 32

d₃₁

g₃₁(×

ε_33τ/

Tc

(pm/V)
Kp
10⁻³Vm/N)
Qm
ε₀
tanδ
(° C.)

Sample J8
115.2
0.502
7.73
44.1
1683.3
0.023
308

Sample J9
105.6
0.489
7.84
49.0
1521.2
0.027
308

Sample J10
61.2
0.290
4.40
75.3
1569
0.033
308

Sample J11
17.6
0.100
1.60
264.1
1227.3
0.029
308

Sample C1
37.6
0.334
9.9
100.6
429
0.036
415

Sample C2
96.1
0.452
7.81
48.4
1389.3
0.026
308

As will be understood from Table 32, the Samples J8 and J9 were remarkably improved over Sample C1 in the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, relative dielectric constant ∈_33τ/∈₀, and dielectric loss tan δ. Further, the Samples J8 and J9 were also improved over the Sample C2 in the piezoelectric d₃₁constant, electromechanical coupling coefficient Kp, and relative dielectric constant ∈_33τ/∈₀and were equally or more superior in the other properties as well.

On the other hand, the Sample J10 was remarkably improved over the Sample C1 in the piezoelectric d₃₁constant, the relative dielectric constant ∈_33τ/∈₀, and the dielectric loss tan δ. Further, it was improved over the Sample C2 in the mechanical quality factor Qm and relative dielectric constant ∈_33τ/∈₀. However, on the other hand, the electromechanical coupling coefficient Kp and piezoelectric g₃₁constant dropped considerably.

Further, the Sample J11 was improved over the Sample C1 in the mechanical quality factor Qm, the relative dielectric constant ∈_33τ/∈₀, and the dielectric loss tan δ. Further, it was improved over the Sample C2 in the mechanical quality factor Qm, but on the other hand the piezoelectric g₃₁constant, the electromechanical coupling coefficient Kp, the piezoelectric g₃₁constant, etc. dropped remarkably.

In this way, the piezoelectric ceramic compositions (Sample J8 and Sample J8) of the present examples are of compositions not containing lead and have superior piezoelectric properties and dielectric properties. Therefore, they are safe to the environment and can be utilized for high performance piezoelectric elements and dielectric elements.

According to our findings, the same effect as in these examples were obtained for the additives which were included in smaller amounts such as 0.0001 mol, while not shown in the present examples.

While the invention has been described with reference to specific embodiments chosen for purpose of illustration, it should be apparent that numerous modifications could be made thereto by those skilled in the art without departing from the basic concept and scope of the invention.

Number	Date	Country	Kind
2002-207208	Jul 2002	JP	national
2003-015282	Jan 2003	JP	national
2003-015283	Jan 2003	JP	national
2003-015284	Jan 2003	JP	national
2003-015285	Jan 2003	JP	national
2003-069060	Mar 2003	JP	national

Number	Name	Date	Kind
6514427	Nishida et al.	Feb 2003	B1
20020060306	Nishida et al.	May 2002	A1

Number	Date	Country
1 032 057	Aug 2000	EP
49-33907	Mar 1974	JP
58-060582	Apr 1983	JP
7-82024	Mar 1995	JP
10-53465	Feb 1998	JP
11-228226	Aug 1999	JP
11-228227	Aug 1999	JP
11-228228	Aug 1999	JP
2001-114560	Apr 2001	JP
2001-240471	Sep 2001	JP
2001-316182	Nov 2001	JP
A-2002-154872	May 2002	JP
2002-193663	Jul 2002	JP
2003-12373	Jan 2003	JP

Piezoelectric ceramic composition and method of production of same, piezoelectric element, and dielectric element

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