Patent Application
20140036004
This is a continuation of International Application No. PCT/JP2013/002426, with an international filing date of Apr. 10, 2013, which claims priority of Japanese Patent Application No. 2012-172636, filed on August 3, Japanese Patent Application No. 2012-172637, filed on August 3, Japanese Patent Application No. 2012-172638, filed on August 3, and Japanese Patent Application No. 2012-172639, filed on August 3, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a piezoelectric film comprising a piezoelectric layer and a method of manufacturing the piezoelectric film. The present invention further relates to an ink jet head comprising the piezoelectric film and a method of forming an image by the head, to an angular velocity sensor comprising the piezoelectric film and a method of measuring an angular velocity by the sensor, and to a piezoelectric generating element comprising the piezoelectric film and a method of generating electric power using the element.
2. Description of the Related Art
Perovskite composite oxide [(Bi, Na)1-β Baβ] TiO3 (hereinafter, referred to as “NBT-BT”) has been recently researched and developed as a non-lead (lead-free) ferroelectric material.
Japanese Patent Publication No. Hei 4-60073B and T. Takenaka et al., Japanese Journal of Applied Physics, Vol. 30, No. 9B, (1991), pp. 2236-2239 disclose that a NBT-BT layer has high piezoelectric performance when the NBT-BT layer has a composition around the Morphotropic Phase Boundary (hereinafter, referred to as “MPB”) having a barium molar ratio β (=[Ba/(Bi+Na+Ba)]) of 3-15%.
Japanese Patent Publication No. 4140796B and E. V. Ramana et al., Solid State Sciences, Vol. 12, (2010), pp. 956-962 disclose (1-α)(Bi,Na,Ba)TiO3-αBiFeO3 where perovskite composite oxide NBT-BT is combined with perovskite oxide BiFeO3. The piezoelectric performance of the (1-α)(Bi,Na,Ba)TiO3-αBiFeO3 is maintained even at a solder reflow temperature of 180 degrees Celsius.
The (1-α) (Bi, Na, Ba) TiO3-αBiFeO3 has also been expected as a non-lead ferroelectric material capable of being used instead of PZT. However, the (1-α) (Bi, Na, Ba) TiO3-αBiFeO3 has lower piezoelectric performance than the PZT.
A ferroelectric material containing (Bi, Na, Ba) TiO3 or BiFeO3 has high dielectric loss. When the dielectric loss is high, the ferroelectric performance and the piezoelectric performance are deteriorated significantly.
An object of the present invention is to provide a non-lead piezoelectric film having high crystalline orientation, low dielectric loss, high polarization-disappear temperature, and high piezoelectric constant.
It is another object of the present invention to provide an ink jet head, an angular velocity sensor, and a piezoelectric generating element, each comprising the non-lead piezoelectric film. It is still another object of the present invention to provide a method of forming an image by this ink jet head, a method of measuring an angular velocity by this angular velocity sensor, and a method of generating electric power using this piezoelectric generating element.
The present invention provides a piezoelectric film comprising:
a NaxM1-x layer having a (001) orientation only; and
a (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer having a (001) orientation only; wherein
the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer is formed on the NaxM1-x layer;
M represents Pt, Ir, or PtIr;
Q represents Fe, Co, Zn0.5Ti0.5, or Mg0.5Ti0.5;
x represents a value of not less than 0.002 and not more than 0.02; and
α represents a value of not less than 0.20 and not more than 0.50.
The spirit of the present invention includes an ink jet head, an angular velocity sensor, and a piezoelectric generating element, each of which comprises the piezoelectric film.
The spirit of the present invention includes a method of measuring an angular velocity by the angular velocity sensor, a method of forming an image by the ink jet head, and a method of generating electric power using the piezoelectric generating element.
The present invention provides a non-lead piezoelectric film having high crystalline orientation, low dielectric loss, high polarization-disappear temperature, and high piezoelectric constant.
The present invention provides an ink jet head comprising the non-lead piezoelectric film and a method of forming an image by the head.
The present invention provides an angular velocity sensor comprising the non-lead piezoelectric film and a method of measuring an angular velocity by the sensor.
The present invention provides a piezoelectric generating element comprising the non-lead piezoelectric film and a method of generating electric power using the element.
Other features, elements, processes, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached drawings.
Embodiments of the present invention are described below with reference to the drawings. In the following description, the same reference numerals are used to designate the same elements and parts, and therefore the overlapping description thereof can be omitted.
The term used in the instant specification is defined as below.
The term “temperature Td” means the temperature at which a polarization included in the piezoelectric layer disappears completely by heating the piezoelectric layer. In other words, the piezoelectric layer completely loses its polarization at a temperature more than the temperature Td. The piezoelectric layer which does not have the polarization fails to serve as a piezoelectric layer. In view of the solder reflow, it is desirable that the temperature Td be not less than 180 degrees Celsius.
[Piezoelectric Film]
The (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 has a (001) orientation only. In other words, the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 does not have an orientation other than a (001) orientation. For example, the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 does not have a (110) orientation. See the comparative examples A1, A2, B1, B2, C1, C2, D1 and D2, which are described later.
Similarly, the NaxM1-x layer 13 has a (001) orientation only.
The character x represents a value of not less 0.002 and not more than 0.02. When the value of x is less than 0.002, the crystalline orientation, the polarization-disappear temperature, and the piezoelectric constant are low. Furthermore, the dielectric loss is high. See the comparative examples A1, B1, C1, D1, and D2, which are described later.
When the value of x is over 0.02, the crystalline orientation, the polarization-disappear temperature, and the piezoelectric constant are low. Furthermore, the dielectric loss is high. See the comparative examples A2, B2, C2, and D2, which are described later.
The value of α is not less than 0.20 and not more than 0.50. When the value of α is less than 0.20, the polarization-disappear temperature is low. See the comparative examples A3, B3, C3, and D3, which are described later.
When the value of α is over 0.50, the crystalline orientation, the polarization-disappear temperature, and the piezoelectric constant are low. Furthermore, the dielectric loss is high. See the comparative examples A4, B4, C4, and D4, which are described later.
It is desirable that these stacked layers be in contact with each other. The (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 serves as a piezoelectric layer. The (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 has a small leak current, high crystallinity, and a high (001) orientation. For this reason, the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 has high polarization-disappear temperature, low dielectric loss, and high piezoelectric performance, although it does not contain lead. The (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 has piezoelectric performance similar to that of the PZT layer.
Typically, the NaxM1-x layer 13 can be formed by sputtering. The NaxM1-x layer 13 can also be formed by a thin film formation technique such as pulsed laser deposition (PLD), chemical vapor deposition (CVD), sol-gel processing, or aerosol deposition (AD).
The thickness of the NaxM1-x layer 13 is not limited. As one example, the NaxM1-x layer 13 has a thickness of not less than approximately 2 nanometers.
The thickness of the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 is also not limited. The thickness thereof is at least 0.5 micrometers but not more than 10 micrometers, for example.
The (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 has a perovskite crystal structure represented by the chemical formula ABO3. The A site is Bi, Na, and Ba. The B site is Ti and Q. The (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 may contain a minute amount of impurities. The impurities typically may be Li and K to substitute for Na, and Sr and Ca to substitute for Ba, in the A site. The impurities typically may be Zr to substitute for Ti in the B site. Examples of the other impurities may include Mn, Co, Al, Ga, Nb, and Ta. Some of these impurities can improve the crystallinity and piezoelectric performance of the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15.
Typically, the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 can be formed by sputtering. The (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 can also be formed by another thin film formation technique such as PLD, CVD, sol-gel processing, or AD.
An example of the material of the second electrode layer 17 is a metal having a low electric resistance. Other examples of the material of the second electrode layer 17 include oxide conductors such as NiO, RuO2, IrO3, SrRuO3, and LaNiO3. The second electrode layer 17 may be composed of two or more kinds of these materials.
A metal layer may be interposed between the second electrode layer 17 and the (Bi, Na)TiO3—BaTiO3 layer 15 to improve the adhesion therebetween. Examples of the material of the metal layer include titanium, tantalum, iron, cobalt, nickel, and chrome. Two or more kinds of metals may be used.
Examples of the substrate 11 are described below:
a silicon substrate;
an oxide substrate having a sodium chloride structure such as a MgO substrate,
an oxide substrate having a perovskite-type structure such as a SrTiO3 substrate, a LaAlO3 substrate, or a NdGaO3 substrate;
an oxide substrate having a corundum-type structure such as a Al2O3 substrate;
an oxide substrate having a spinel-type structure such as a MgAl2O4 substrate;
an oxide substrate having a rutile-type structure such as a TiO2 substrate; and
an oxide substrate having a crystal structure of cubic system such as a (La, Sr) (Al, Ta) O3 substrate or an yttria-stabilized zirconia (YSZ) substrate.
Desirably, a silicon monocrystalline substrate or a MgO monocrystalline substrate may be used.
An interlayer may be formed on the surface of the substrate 11 by an epitaxial growth method. An example of the material of the interlayer is yttria-stabilized zirconia (YSZ).
Other examples of the material of the interlayer are described below:
materials having a fluorite-type structure such as CeO2,
materials having a sodium chloride structure such as MgO, BaO, SrO, TiN, and ZrN,
materials having a perovskite-type structure such as SrTiO3, LaAlO3, (La, Sr) MnO3, and (La, Sr) CoO3; and
materials having a spinel-type structure such as γ-Al2O3 and MgAl2O4.
Two or more kinds of these materials may be used. As one example, the substrate 11 may be a laminate of CeO2/YSZ/Si.
A metal layer is interposed between the substrate 11 and the NaxM1-x layer 13 to improve the adhesion therebetween. Examples of the material of the metal layer include Ti, Ta, Fe, Co, Ni, and Cr. Ti is desirable.
The following examples describe the present invention in more detail.
The following examples are composed of the example A, the example B, the example C, and the example D.
In the example A, Q of the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 is Fe. The example A is composed of the example A1—the example A10 and the comparative example A1—the comparative example A4.
In the example B, Q of the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 is Co. The example B is composed of the example B1—the example B10 and the comparative example B1—the comparative example B4.
In the example C, Q of the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 is Zn0.5Ti0.5. The example C is composed of the example C1—the example C10 and the comparative example C1—the comparative example C4.
In the example D, Q of the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 is Mg0.5Ti0.5. The example D is composed of the example D1—the example D10 and the comparative example D1—the comparative example D4.
A piezoelectric film shown in
First, a NaxM1-x (x=0.01, M=Pt) layer 13 having a (001) orientation only was formed on a MgO (100) monocrystalline substrate 11 by a sputtering method. The NaxM1-x (x=0.01, M=Pt) layer 13 had a thickness of 250 nanometers. The condition of the sputtering method is described below:
Target: Same composition as above
Gas atmosphere: Argon
RF power: 15 W
Substrate temperature: 300 degrees Celsius
The formed NaxM1-x (x=0.01, M=Pt) layer 13 was subjected to an X-ray diffraction analysis (XRD). As a result, it was observed that the NaxM1-x (x=0.01, M=Pt) layer 13 had a (001) orientation only.
The composition of the NaxM1-x (x=0.01, M=Pt) layer 13 was analyzed by an energy dispersive X-ray spectroscopy (SEM-EDX). It was confirmed that the composition of Na and Pt contained in the NaxM1-x (x=0.01, M=Pt) layer 13 was the same as the composition of the target.
The (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 having a (001) orientation only was formed on the NaxM1-x (x=0.01, M=Pt) layer 13 by RF magnetron sputtering. In the example A1, Q was Fe. In the example A1, α was 0.2. The (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 had a thickness of 2.7 micrometers. This (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 had a composition around MPB.
The condition of the sputtering method of the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 is described below.
Target: Same composition as above
Atmosphere: Mixed gas of argon and oxygen (Flow ratio of Ar/O2:50/50)
RF power: 170 W
Substrate temperature: 650 degrees Celsius
The formed (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 was subjected to an X-ray diffraction analysis to analyze the crystal structure thereof. The X-ray diffraction analysis was carried out in such a manner that an X-ray beam was made incident from above the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15.
Then, a gold layer (thickness: 100 nanometers) was formed by evaporation on the surface of the (1-α) (Bi, Na, Ba)TiO3-αBiQO3 layer 15. This gold layer served as the conductive layer 17. In this way, the piezoelectric film according to the example A1 was fabricated.
Using a platinum layer and the gold layer, the ferroelectric performance and the piezoelectric performance of the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 were evaluated.
As shown in
The polarization-disappear temperature, namely, the temperature Td, of the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 was measured as below.
The (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 was set in a thermostatic oven. The P-E hysteresis curve of the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 was measured with an increase in temperature.
The temperature Td was measured in accordance with Journal of the American Ceramic Society 93 [4] (2010) 1108-1113.
The temperature Td of the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 according to the example A1 was a high value of 188 degrees Celsius. This means that the piezoelectric performance of the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 is maintained under a solder reflow temperature (180 degrees Celsius).
The piezoelectric performance of the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 was evaluated in the following manner. The (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 was cut into a strip with a width of 2 mm and worked into a cantilever shape. A potential difference was applied between the platinum layer and the gold layer, and the cantilever was displaced by the electric field generated between the two layers. The resulting displacement of the cantilever was measured with a laser displacement meter.
These results are shown in Table 1 and Table 2.
An example similar to the example A1 was conducted, except that x=0.002. The results are shown in Table 1 and Table 2.
An example similar to the example A1 was conducted, except that x=0.02. The results are shown in Table 1 and Table 2.
An example similar to the example A1 was conducted, except that α=0.3. The results are shown in Table 1 and Table 2.
An example similar to the example A1 was conducted, except that α=0.4. The results are shown in Table 1 and Table 2.
An example similar to the example A1 was conducted, except that α=0.5. The results are shown in Table 1 and Table 2.
An example similar to the example A1 was conducted, except that x=0.002 and α=0.5. The results are shown in Table 1 and Table 2.
An example similar to the example A1 was conducted, except that x=0.02 and α=0.5. The results are shown in Table 1 and Table 2.
An example similar to the example A1 was conducted, except that M=Ir. The results are shown in Table 1 and Table 2.
An example similar to the example A1 was conducted, except that M=Ir0.5Pt0.5. The results are shown in Table 1 and Table 2.
An example similar to the example A1 was conducted, except that x=0.
Similarly, the present inventors tried the evaluation of the ferroelectric performance and the piezoelectric performance of the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 in the comparative example A1. However, it was difficult to measure the P-E hysteresis curve accurately, since the leak current in the piezoelectric film was very high (see
The (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 according to the comparative example A1 had a tan δ of 36%. It was difficult to measure the accurate temperature Td and the accurate piezoelectric constant d31, since the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 of the comparative example A1 had such a high leak current. The estimated temperature Td was approximately 152 degrees Celsius.
An example similar to the example A1 was conducted, except that x=0.05.
The reflection peak derived from the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 having a (001) orientation was also observed in the comparative example A2. However, another reflection peak derived from another crystalline orientation (110) included in the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 was also observed.
An example similar to the example A1 was conducted, except that α=0.1.
An example similar to the example A1 was conducted, except that α=0.6.
As is clear from Table 1 and Table 2, if both of the following items (a) and (b) are satisfied, the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 (Q=Fe) has high crystalline orientation, low dielectric loss, high polarization-disappear temperature, and high piezoelectric constant.
(a) the value of x is not less than 0.002 and not more than 0.02.
(b) the value of α is not less than 0.2 and not more than 0.5.
As is clear from the example A2, the example A7, and the comparative example A1, it is necessary that the value of x is not less than 0.002.
As is clear from the example A3, the example A8, and the comparative example A2, it is necessary that the value of x is not more than 0.02.
As is clear from the example A1, the example A2, the example A3, and the comparative example A3, it is necessary that the value of α is not less than 0.2.
As is clear from the example A6, the example A7, the example A8, and the comparative example A4, it is necessary that the value of α is not more than 0.5.
An example similar to the example A was conducted, except that Co was used instead of Fe as Q of the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15. Table 3 and Table 4 show the results of the example B, which is composed of the example B1—the example B10 and the comparative example B1—the comparative example B4.
Similarly to the example A, as is clear from Table 3 and Table 4, if both of the following items (a) and (b) are satisfied, the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 (Q=Co) has high crystalline orientation, low dielectric loss, high polarization-disappear temperature, and high piezoelectric constant.
(a) the value of x is not less than 0.002 and not more than 0.02.
(b) the value of α is not less than 0.2 and not more than 0.5.
An example similar to the example A was conducted, except that Zn0.5Ti0.5 was used instead of Fe as Q of the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15. Table 5 and Table 6 show the results of the example C, which is composed of the example C1—the example C10 and the comparative example C1—the comparative example C4.
Similarly to the example A, as is clear from Table 5 and Table 6, if both of the following items (a) and (b) are satisfied, the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 (Q=Zn0.5Ti0.5) has high crystalline orientation, low dielectric loss, high polarization-disappear temperature, and high piezoelectric constant.
(a) the value of x is not less than 0.002 and not more than 0.02.
(b) the value of α is not less than 0.2 and not more than 0.5.
An example similar to the example A was conducted, except that Mg0.5Ti0.5 was used instead of Fe as Q of the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15. Table 7 and Table 8 show the results of the example D, which is composed of the example D1—the example D10 and the comparative example D1—the comparative example D4.
Similarly to the example A, as is clear from Table 7 and Table 8, if both of the following items (a) and (b) are satisfied, the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 (Q=Mg0.5Ti0.5) has high crystalline orientation, low dielectric loss, high polarization-disappear temperature, and high piezoelectric constant.
(a) the value of x is not less than 0.002 and not more than 0.02.
(b) the value of α is not less than 0.2 and not more than 0.5.
The ink jet head, the angular velocity sensor, and the piezoelectric generating element of the present invention each comprising the above-mentioned piezoelectric film are described. For more detail, see International publication No. 2010/047049. U.S. Pat. No. 7,870,787 and Chinese Laid-open patent application publication No. 101981718 are the United States patent publication and the Chinese laid-open patent application publication which correspond to International publication No. 2010/047049, respectively.
[Ink Jet Head]
An ink jet head of the present invention will be described below with reference to
A reference character A in
The actuator part B has piezoelectric films and vibration layers that are aligned over the corresponding pressure chambers 102 respectively in plan view. In
The ink passage member C has a plurality of common liquid chambers 105 arranged in stripes in plan view. In
In
As surrounded by the dashed-line in
[Image Forming Method by Ink Jet Head]
The image forming method of the present invention includes, in the above-described ink jet head of the present invention, a step of applying a voltage to the piezoelectric layer through the first and second electrodes (that is, the individual electrode layer and the common electrode layer) to displace, based on the piezoelectric effect, the vibration layer in its film thickness direction so that the volumetric capacity of the pressure chamber changes; and a step of ejecting the ink from the pressure chamber by the displacement.
The voltage to be applied to the piezoelectric layer is changed with the relative position between the ink jet head and an object like a sheet of paper, on which an image is to be formed, being changed, so as to control the timing of ink ejection from the ink jet head and the amount of ink ejected therefrom. As a result, an image is formed on the surface of the object. The term “image” used in the present description includes a character. In other words, according to the present method of forming an image, a letter, a picture, or a figure is printed to a print target such as a sheet of paper. With this method, a picturesque image can be printed.
[Angular Velocity Sensor]
The angular velocity sensor 21a shown in
The substrate 200 has a stationary part 200a and a pair of arms (vibration parts 200b) extending in a predetermined direction from the stationary part 200a. The direction in which the vibration parts 200b extend is the same as the direction in which the central axis of rotation L of the angular velocity detected by the angular velocity sensor 21 extends. More specifically, it is the Y direction in
The material of the substrate 200 is not limited. The material is, for example, Si, glass, ceramic, or metal. A monocrystalline Si substrate can be used as the substrate 200. The thickness of the substrate 200 is not limited as long as the functions of the angular velocity sensor 21a can develop. More particularly, the substrate 200 has a thickness of at least 0.1 mm but not more than 0.8 mm. The thickness of the stationary part 200a can be different from that of the vibration part 200b.
The piezoelectric film 208 is bonded to the vibration part 200b. The piezoelectric film 208 is the piezoelectric film described in the item titled as “Piezoelectric film”. As shown in
The second electrode 205 has an electrode group including a drive electrode 206 and a sense electrode 207. The drive electrode 206 applies a driving voltage that oscillates the vibration part 200b to the piezoelectric layer 15. The sense electrode 207 measures a deformation of the vibration part 200b caused by an angular velocity applied to the vibration part 200b. That is, the vibration part 200b usually oscillates in the width direction thereof (the X direction in
In the angular velocity sensor of the present invention, one of the first electrode and the second electrode selected therefrom can be composed of an electrode group including the drive electrode and the sense electrode. In the angular velocity sensor 21a shown in
The first electrode 202, the drive electrode 206, and the sense electrode 207 have connection terminals 202a, 206a, and 207a, respectively, formed at the end portions thereof. The shape and position of each of the connection terminals are not limited. In
In the angular velocity sensor shown in
The angular velocity sensor of the present invention may have two or more vibration part groups each consisting of a pair of vibration parts 200b. Such an angular velocity sensor can serve as a biaxial or triaxial angular velocity sensor capable of measuring angular velocities with respect to a plurality of central axes of rotation. The angular velocity sensor shown in
[Method of Measuring Angular Velocity By Angular Velocity Sensor]
The angular velocity measuring method of the present invention uses the angular velocity sensor of the present invention, and includes the steps of: applying a driving voltage to the piezoelectric layer to oscillate the vibration part of the substrate; and measuring a deformation of the vibration part caused by an angular velocity applied to the oscillating vibration part to obtain a value of the applied angular velocity. The driving voltage is applied between the drive electrode and one of the first electrode and the second electrode (the other electrode) that serves neither as the drive electrode nor as the sense electrode, and thus the driving voltage is applied to the piezoelectric layer. The sense electrode and the other electrode measure the deformation of the oscillating vibration part caused by the angular velocity.
Hereinafter, the angular velocity measuring method by the angular velocity sensor 21a shown in
When an angular velocity ω with respect to the central axis of rotation L is applied to the angular velocity sensor 21a in which the vibration parts 200b are oscillating, the vibration parts 200b are deflected respectively in their thickness direction (the Z direction) by Coriolis force. In the case where the respective vibration parts 200b are oscillating in the opposite direction mode, they are deflected in the opposite directions by the same degree. The piezoelectric layer 15 bonded to the vibration part 200b is also deflected according to this deflection of the vibration part 200b. As a result, a potential difference is generated between the first electrode 202 and the sense electrode 207 in accordance with the deflection of the piezoelectric layer 15, that is, the magnitude of the generated Coriolis force. The angular velocity ω applied to the angular velocity sensor 21a can be measured by measuring the magnitude of the potential difference.
The following relationship between a Coriolis force Fc and the angular velocity ω is true:
Fc=2mvω
where v is the velocity of the oscillating vibration part 200b in the oscillation direction, and m is the mass of the vibration part 200b. As shown in this equation, the angular velocity ω can be calculated from the Coriolis force Fc.
[Piezoelectric Generating Element]
The piezoelectric generating element 22a shown in
The substrate 300 has a stationary part 300a, and a vibration part 300b having a beam extending in a predetermined direction from the stationary part 300a. The material of the stationary part 300a can be the same as the material of the vibration part 300b. These materials may, however, be different from each other. The stationary part 300a and the vibration part 300b made of materials different from each other may be bonded to each other.
The material of the substrate 300 is not limited. The material is, for example, Si, glass, ceramic, or metal. A monocrystalline Si substrate can be used as the substrate 300. The substrate 300 has a thickness of, for example, at least 0.1 mm but not more than 0.8 mm. The stationary part 300a may have a thickness different from that of the vibration part 300b. The thickness of the vibration part 300b can be adjusted for efficient power generation by changing the resonance frequency of the vibration part 300b.
A weight load 306 is bonded to the vibration part 300b. The weight load 306 adjusts the resonance frequency of the vibration part 300b. The weight load 306 is, for example, a vapor-deposited thin film of Ni. The material, shape, and mass of the weight load 306, as well as the position to which the weight load 306 is bonded can be adjusted according to a desired resonance frequency of the vibration part 300b. The weight load 306 may be omitted. The weight load 306 is not necessary when the resonance frequency of the vibration part 300b is not adjusted.
The piezoelectric film 308 is bonded to the vibration part 300b. The piezoelectric film 308 is the piezoelectric film described in the item titled as “Piezoelectric film”. As shown in
In the piezoelectric generating element shown in
In the piezoelectric generating element shown in
When the piezoelectric generating element of the present invention has a plurality of vibration parts 300b, an increased amount of electric power can be generated. Such a piezoelectric generating element can be applied to mechanical vibrations containing a wide range of frequency components if the plurality of vibration parts 300b have different resonance frequencies.
[Method of Generating Electric Power Using Piezoelectric Generating Element]
The above-described piezoelectric generating element of the present invention is vibrated to obtain electric power through the first electrode and the second electrode.
When mechanical vibration is applied externally to the piezoelectric generating element 22a, the vibration part 300b starts vibrating to produce vertical deflection with respect to the stationary part 300a. The piezoelectric effect produced by this vibration generates an electromotive force across the piezoelectric layer 15. As a result, a potential difference is generated between the first electrode 302 and the second electrode 305 that sandwich the piezoelectric layer 15 therebetween. The higher piezoelectric performance of the piezoelectric layer 15 generates a larger potential difference between the first and second electrodes. Particularly in the case where the resonance frequency of the vibration part 300b is close to the frequency of mechanical vibration to be applied externally to the element, the amplitude of the vibration part 300b increases and thus the electric power generation characteristics are improved. Therefore, the weight load 306 is preferably used to adjust the resonance frequency of the vibration part 300b to be close to the frequency of mechanical vibration applied externally to the element.
A piezoelectric film comprising the (1-α) (Bi, Na, Ba) TiO3-αBiQO3 layer 15 can be used for an ink jet head, an angular velocity sensor and a piezoelectric generating element.
While the present invention has been described with respect to preferred embodiments thereof, it will be apparent to those skilled in the art that the disclosed invention may be modified in numerous ways and may assume many embodiments other than those specifically described above. Accordingly, it is intended by the appended claims to cover all modifications of the invention that fall within the true spirit and scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-172636 | Aug 2012 | JP | national |
| 2012-172637 | Aug 2012 | JP | national |
| 2012-172638 | Aug 2012 | JP | national |
| 2012-172639 | Aug 2012 | JP | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2013/002426 | Apr 2013 | US |
| Child | 14029638 | US |
