Dielectric ceramic for microwave applications

Description

FIELD OF THE INVENTION
This invention concerns a dielectric ceramic for microwave applications, and in particular, a dielectric ceramic composition for microwave applications having a high dielectric constant .epsilon. .sub.r, a high unloaded Q, and temperature coefficient .tau. .sub.f which can be made to vary above or below zero by varying the composition.
BACKGROUND OF THE INVENTION
It is known that in general, for dielectric resonators for microwave circuits or temperature compensation ceramic (porcelain) capacitors or the like, dielectric ceramic (porcelain) compositions are required to have a high dielectric constant .epsilon. .sub.r and unloaded Q (Q.sub.u =1/tan.delta.), and it must be possible to design them with any desired value for the temperature coefficient .tau. .sub.f of the resonant frequency above or below zero, i.e., with a positive or negative temperature coefficient. Conventionally, such compositions included Bao.TiO.sub.2 systems, MgTiO.sub.3.CaO systems, ZrO.sub.2.SnO.sub.2.TiO.sub.2 systems, and BaO.TiO.sub.2.Sm.sub.2 O.sub.3.La.sub.2 O.sub.3 systems (see for example Japanese Patent Kokoku Publication No. 61-14606).
When dielectric resonators or capacitors were manufactured with these compositions, however, their dielectric constant .epsilon. .sub.r was 60 to 80 when their temperature coefficient .tau. .sub.f was in the region of 0 (ppm/.degree.C.), and this value of dielectric constant was too small to permit the resonator to be made compact.
SUMMARY OF THE INVENTION
This invention was conceived to overcome the above problems. An objective of the invention is therefore to provide a dielectric ceramic for microwave applications with high dielectric constant .epsilon. .sub.r and unloaded Q even when the temperature coefficient is in the region of 0 (ppm/.degree.C.).
According to one aspect of the invention, a dielectric ceramic for microwave applications is comprised of barium oxide (BaO), titanium dioxide (TiO.sub.2), samarium oxide (Sm.sub.2 O.sub.3), lanthanum oxide (La.sub.2 O.sub.3) and neodymium oxide (Nd.sub.2 O.sub.3) represented by the formula:
X BaO.Y TiO.sub.2.Z {(Sm.sub.2 O.sub.3).sub.1-W1-W2 (La.sub.2 O.sub.3).sub.W1 (Nd.sub.2 O.sub.3).sub.W2 }
where X, Y, Z lie in the ranges:
11.0.ltoreq.X.ltoreq.22.0
60.0.ltoreq.Y.ltoreq.75.0
6.0.ltoreq.Z.ltoreq.28.0
X+Y+Z=100
expressed in mole %, and
0<W.sub.1 .ltoreq.0.35
0<W.sub.2 <1
0<(1-W.sub.1 -W.sub.2)<1
where W.sub.1, W.sub.2 and (1-W.sub.1 -W.sub.2) are mole ratios.
In addition to BaO, TiO.sub.2, Sm.sub.2 O.sub.3, La.sub.2 O.sub.3, and Nd.sub.2 O.sub.3, which are the main constituents, the dielectric ceramic may also contain MnO.sub.2 as a supplementary constituent to the extent of no more than 3 wt %.
In addition to BaO, TiO.sub.2, Sm.sub.2 O.sub.3, La.sub.2 O.sub.3, and Nd.sub.2 O.sub.3, which are the main constituents, the dielectric ceramic may also contain Al.sub.2 O.sub.3 as a supplementary constituent to the extent of no more than 3 wt %.
According to another aspect of the invention, a dielectric ceramic for microwave applications is comprised of barium oxide (BaO), titanium dioxide (TiO.sub.2), samarium oxide (Sm.sub.2 O.sub.3), lanthanum oxide (La.sub.2 O.sub.3), neodymium oxide (Nd.sub.2 O.sub.3) and bismuth oxide (Bi.sub.2 O.sub.3), represented by the formula:
X BaO.Y TiO.sub.2.Z {(Sm.sub.2 O.sub.3).sub.1-W1-W2 (La.sub.2 O.sub.3).sub.W1 (Nd.sub.2 O.sub.3).sub.W2 }.V Bi.sub.2 O.sub.3
where X, Y, Z and V lie in the ranges:
11.5.ltoreq.X.ltoreq.21.0
60.0.ltoreq.Y.ltoreq.76.0
6.5.ltoreq.Z.ltoreq.26.0
0.1.ltoreq.V.ltoreq.5.0
X+Y+Z+V=100
expressed in mole %, and
0<W.sub.1 <1
0<W.sub.2 <1
0<(1-W.sub.1 -W.sub.2)<1,
where W.sub.1, W.sub.2 and (1-W.sub.1 -W.sub.2) are mole ratios.
In addition to the above described main constituents, the dielectric ceramic may also contain MnO.sub.2 as a supplementary constituent, to the extent of no more than 2 wt %.
In addition to the above described main constituents, the dielectric ceramic may also contain cerium oxide (CeO.sub.2), as a supplementary constituent, to the extent of no more than 5 wt %, this amount corresponding to 0.0606 mole per mole of the main constituents.
In addition to the above described main constituents, the dielectric ceramic may also contain lead oxide (PbO), as a supplementary constituent, to the extent of no more than 5 wt %, this corresponding to 0.0463 mole per mole of the main constituents.
In addition to the above described main constituents, the dielectric ceramic may also contain aluminum oxide (Al.sub.2 O.sub.3), as a supplementary constituent, to the extent of no more than 3 wt %, this corresponding to 0.0609 mole per mole of the main constituents.
In this invention, the constituents of the dielectric ceramic for microwave applications are specified within the above limits, as a result, as will be clear from the following experimental results, the dielectric constant .epsilon. .sub.r and unloaded Q are high even if said temperature coefficient .tau. .sub.f is in the region of 0 (ppm/.degree.C.), and the temperature coefficient .tau. .sub.f can also be given any desired value above or below 0, i.e., positive or negative, by varying the composition.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
We shall now described this invention in more detail with reference to specific examples.
In the following description, Tables B1, B2, C1, A1, A2, D1, D2 and D3 that form the last part of the specification will be referred to. These Tables shows the results of the experiments or measurements on the examples according to the invention, and comparative examples.
In the attached Tables, sample numbers marked with the symbols "*" are comparative samples which are outside the scope of the invention, and other samples are examples according to the invention. Also, in the Tables, as well as in the following description, "wt %" denote percentage in weight.
EXAMPLE B
BaCO.sub.3, TiO.sub.2, Sm.sub.2 O.sub.3, La.sub.2 O.sub.3, Nd.sub.2 O.sub.3 and MnCO.sub.3 of high purity were taken as starting materials, and mixed in the proportions shown in the attached Table B1 and Table B2. This mixture was calcined in air at 1060.degree. C. for 2 hours. The calcined material was pulverized in a pot mill with pure water, dewatered and dried to obtain a powder. To the powder was added a binder to obtain a granule, which was then classified by passing through a 32 mesh sieve. The granule obtained was molded by a die at a pressure of 1 to 3 ton/cm.sup.2 to form a circular plate of diameter 16 mm and thickness 9 mm. This molded product was then placed in a high purity alumina case and fired at a suitable temperature in the range 1250.degree. C. to 1500.degree. C. for 2 hours so as to obtain a dielectric ceramic material.
The dielectric constant .epsilon. .sub.r and Q.sub.u of the material were measured by the Hakki-Coleman method. Further, the temperature coefficient .tau. .sub.f of the resonant frequency was found by equation (1) below from the resonant frequencies at the temperatures -40.degree. C. and +85.degree. C., and the resonant frequency at the temperature 20.degree. C. taken as a reference, and the experimental results were shown in Tables B1 and B2 attached. The resonant frequency in these measurements was 3 to 4 GHz. ##EQU1## where: f (20.degree. C.)=resonant frequency at 20.degree. C.
f (85.degree. C.)=resonant frequency at 85.degree. C.
f (-40.degree. C.)=resonant frequency at -40.degree. C.
.DELTA. T=measured temperature difference. In this case, .DELTA. T=85-(-40)=125.degree. C.
According to the results of Table B1, if the amount of BaO in the composition is less than 11.0 mole % or greater than 22.0 mole %, or alternatively if the amount of TiO.sub.2 is less than 60.0 mole % or greater than 75.0 mole %, the unloaded Q (Q.sub.u) becomes small and the temperature coefficient .tau. .sub.f increases, which is undesirable. Further, if the total amount Z of rare earth oxides (Sm.sub.2 O.sub.3, La.sub.2 O.sub.3, Nd.sub.2 O.sub.3) is less than 6.0 mole % or greater than 28.0 mole %, the dielectric constant .epsilon. .sub.r and unloaded Q (Q.sub.u) again become small and the temperature coefficient .tau. .sub.f increases, which is undesirable. Further, if the mole ratio W.sub.1 (La.sub.2 O.sub.3) exceeds 0.35, the temperature coefficient .tau. .sub.f is too large which is undesirable. Further, if the mole ratio W.sub.2 (Nd.sub.2 O.sub.3) or (1-W.sub.1 -W.sub.2) (Sm.sub.2 O.sub.3) is zero, the temperature coefficient .tau. .sub.f is either too negative or too positive, which is undesirable.
From the above results, therefore, it was found that if the composition of the main constituents is represented by:
X BaO.Y TiO.sub.2.Z {(Sm.sub.2 O.sub.3).sub.1-W1-W2 (La.sub.2 O.sub.3).sub.W1 (Nd.sub.2 O.sub.3).sub.W2 }
where
11.0.ltoreq.X.ltoreq.22.0
60.0.ltoreq.Y.ltoreq.75.0
6.0.ltoreq.Z.ltoreq.28.0
X+Y+Z=100
where the mole ratios are specified respectively by:
0<W.sub.1 .ltoreq.0.35
0<W.sub.2 <1
0<(1-W.sub.1 -W.sub.2)<1
the composition is suitable for a dielectric ceramic for microwave applications.
Table B2 shows the results of measurements carried out on dielectric ceramics comprised of BaO, TiO.sub.2, Sm.sub.2 O.sub.3, La.sub.2 O.sub.3 and Nd.sub.2 O.sub.3 as main constituents with the further addition of MnO.sub.2, together with the results for comparative examples. By increasing the amount of MnO.sub.2, the unloaded Q (Q.sub.u) can be increased and the temperature coefficient .tau. .sub.f of the resonant frequency can be controlled.
If the amount of MnO.sub.2 exceeds 3 wt %, however, the unloaded Q (Q.sub.u) decreases and the temperature coefficient .tau. .sub.f increases which is undesirable.
EXAMPLE C
BaCO.sub.3, TiO.sub.2, Sm.sub.2 O.sub.3, La.sub.2 O.sub.3, Nd.sub.2 O.sub.3 and Al.sub.2 O.sub.3 of high purity were taken as starting materials, weighed out in the compositional proportions shown in the attached Table C1 (In Table C1, and other tables, the marks .sub." signify "same as above"), and mixed with pure water in a pot mill. In this Example, the main constituents, i.e. BaCO.sub.3, TiO.sub.2, Sm.sub.2 O.sub.3, La.sub.2 O.sub.3 and Nd.sub.2 O.sub.3, were mixed in two different proportions, and the amount of Al.sub.2 O.sub.3 added as a supplementary constituent was varied.
This mixture was calcined in air at 1060.degree. C. for 2 hours. The calcined material was processed in the same manner as in Example B to obtain the molded circular plate. The molded product was then placed in a high purity alumina case and fired at a suitable temperature in the range 1250.degree. C. to 1400.degree. C. so as to obtain a dielectric ceramic.
The dielectric constant .epsilon. .sub.r and unloaded Q (Q.sub.u) of the material were measured in the same manner as in the Embodiment B, and the temperature coefficient .tau. .sub.f of the resonant frequency was found by equation (1).
The results of the experiments were shown in the attached Table C1.
According to the experimental results of Table C1, if the amount of Al.sub.2 O.sub.3 added to the composition is no greater than 3 wt % with respect to the main constituents, there is not much change of dielectric constant .epsilon. .sub.r and unloaded Q (Q.sub.u), and in particular, if the amount is 0.2 wt %, unloaded Q (Q.sub.u) increases. Further, as the amount of Al.sub.2 O.sub.3 added increases, the temperature coefficient .tau. .sub.f varies largely in the negative direction. If on the other hand the amount of Al.sub.2 O.sub.3 is greater than 3 wt %, i.e. in the case of Sample No. 5 and No. 10, the dielectric constant .epsilon. .sub.r and unloaded Q (Q.sub.u) becomes smaller and the temperature coefficient .tau. .sub.f becomes highly negative, which is undesirable.
From the above results, therefore, it was found that if the composition is represented by:
X BaO.Y TiO.sub.2. Z {(Sm.sub.2 O.sub.3).sub.1-W1-W2 (La.sub.2 O.sub.3).sub.W1 (Nd.sub.2 O.sub.3).sub.W2 }
with respect to the main constituents, where:
11.0.ltoreq.X.ltoreq.22.0
60.0.ltoreq.Y.ltoreq.75.0
6.0.ltoreq.Z.ltoreq.28.0
X+Y+Z=100
expressed in mole %, where the mole ratios are specified respectively by:
O<W.sub.1 .ltoreq.0.35
O<W.sub.2 <1
O<(1-W.sub.1 -W.sub.2)<1.00
and where Al.sub.2 O.sub.3 is added to the main constituents to the extent of no more than 3 wt % (excluding 0 wt %), the composition is suitable as a dielectric ceramic for microwave applications. The 3 wt % of Al.sub.2 O.sub.3 corresponds to 0.0563 mole of Al.sub.2 O.sub.3 per mole of the main constituents, consisting of BaO, TiO.sub.2, Sm.sub.2 O.sub.3, La.sub.2 O.sub.3 and Nd.sub.2 O.sub.3.
EXAMPLE A
BaCO.sub.3, TiO.sub.2, Sm.sub.2 O.sub.3, La.sub.2 O.sub.3, Nd.sub.2 O.sub.3 and Bi.sub.2 O.sub.3 of high purity were taken as starting materials, and mixed with pure water for 20 to 24 hours in a pot mill in the proportions shown in the attached Table A1 and Table A2. After dewatering the mixture and drying it, the mixed powder was calcined in a high purity alumina case at 1060.degree. C. for 2 hours. The calcined material was processed in the same manner as in Example B to obtain the molded circular plate. This molded product was then placed in a high purity alumina case and fired at a suitable temperature in the range 1250.degree. C. to 1450.degree. C. for 2 hours so as to obtain a dielectric ceramic.
The dielectric constant .epsilon. .sub.r and unloaded Q (Q.sub.u) of the material were measured in the same manner as in the Embodiment B, and the temperature coefficient .tau. .sub.f of the resonant frequency was found by equation (1).
The results of the experiments were shown in the attached Table A1.
According to the results of Table A1, if the amount of BaO in the composition is less than 11.5 mole % or greater than 21.0 mole %, or alternatively if the amount of TiO.sub.2 is less than 60.0 mole % or greater than 76.0 mole %, the unloaded Q (Q.sub.u) becomes small and the temperature coefficient .tau. .sub.f increases, which is undesirable. Further, if the amount Z of rare earth oxides (Sm.sub.2 O.sub.3, la.sub.2 O.sub.3, Nd.sub.2 O.sub.3) is less than 6.5 mole % or greater than 26.0 mole %, the dielectric constant .epsilon. .sub.r and unloaded Q (Q.sub.u) again become small and the temperature coefficeint .tau. .sub.f increases, which is undesirable.
Further, as the amount of Bi.sub.2 O.sub.3 increases, dielectric constant .epsilon. .sub.r and unloaded Q (Q.sub.u) improve, but if it exceeds 5 mole %, unloaded Q (Q.sub.u) decreases which is undesirable. Further, if the mole ratio W.sub.1 (La.sub.2 O.sub.3), W.sub.2 (Nd.sub.2 O.sub.3) or (1-W.sub.1 -W.sub.2) (Sm.sub.2 O.sub.3) are zero, the unloaded Q (Q.sub.u) is small or the temperature coefficient .tau. .sub.f is high, which is undesirable.
From the above results, therefore, it was found that if the composition of the main constituents is represented by:
X BaO.Y TiO.sub.2.Z {(Sm.sub.2 O.sub.3).sub.1-W1-W2 (La.sub.2 O.sub.3).sub.W1 (Nd.sub.2 O.sub.3).sub.W2 }.V Bi.sub.2 O.sub.3
where
11.5.ltoreq.X.ltoreq.21.0
60.0.ltoreq.Y.ltoreq.76.0
6.5.ltoreq.Z.ltoreq.26.0
0.1.ltoreq.V.ltoreq.5.0
X+Y+Z+V=100
where the mole ratios are specified respectively by:
0<W.sub.1 <1
0<W.sub.2 <1
0<(1-W.sub.1 -W.sub.2)<1
the composition is suitable for a dielectric ceramic for microwave applications.
Table A2 shows the results of measurements carried out on dielectric ceramics comprised of BaO, TiO.sub.2, Sm.sub.2 O.sub.3, La.sub.2 O.sub.3, Nd.sub.2 O.sub.3 and Bi.sub.2 O.sub.3 as main constituents with the further addition of MnO.sub.2, together with the results for Comparative Examples.
By increasing the amount of MnO.sub.2, the unloaded Q (Q.sub.u) can be increased and the temperature coefficient .tau. .sub.f of the resonant frequency can be controlled. The sinterability of this dielectric ceramic composition also improved.
If the amount of MnO.sub.2 exceeds 2 wt %, however, the unloaded Q (Q.sub.u) decreases and the sinterability of the composition also declines, which is undesirable.
EXAMPLE D1
BaCO.sub.3, TiO.sub.2, Sm.sub.2 O.sub.3, La.sub.2 O.sub.3, Na.sub.2 O.sub.3, Bi.sub.2 O.sub.3, and CeO.sub.2 of high purity were taken as starting materials, weighted out in the proportions shown in the attached Table D1, and mixed with pure water in a pot mill. In this Example, the main constituents, i.e. BaCO.sub.3, TiO.sub.2, Sm.sub.2 O.sub.3, La.sub.2 O.sub.3, Nd.sub.2 O.sub.3 and Bi.sub.2 O.sub.3, were mixed in two different proportions, and the amount of CeO.sub.2 added as a supplementary constituent was varied.
This mixture was calcined in air at 1060.degree. C. for 2 hours. The calcined material was processed in the same manner as in Example B to obtain the molded circular plate. This molded product was then placed in a high purity alumina case and fired at a suitable temperature in the range 1250.degree. C. to 1400.degree. C. for 2 hours so as to obtain a dielectric ceramic.
The dielectric constant .epsilon. .sub.r and unloaded Q (Q.sub.u) of the material were measured in the same manner as in the Embodiment B, and the temperature coefficient .tau. .sub.f of the resonant frequency was found by equation (1).
The results of the experiments were shown in the attached Table D1.
According to the measurement results of Table D1, as the amount of cerium oxide (CeO.sub.2) is increased with respect to the main constituents, dielectric constant .epsilon. .sub.r and unloaded Q (Q.sub.u) decrease after passing through a maximum, while the temperature coefficient .tau. .sub.f increases after passing through a minimum. The dielectric constant .epsilon. .sub.r exhibits a maximum of .epsilon. .sub.r =89.5 when addition of CeO.sub.2 is 0.2 wt %, and unloaded Q (Q.sub.u) exhibits a maximum of 2310 when addition of CeO.sub.2 is 3 wt %. Subsequently, both dielectric constant .epsilon. .sub.r and unloaded Q (Q.sub.u) decline. It was found that for compositions where the addition of CeO.sub.2 exceeds 5 wt %, i.e. Sample No. 6 and No. 12, dielectric constant .epsilon. .sub.r falls to a very low value of approx. 40, which is undesirable.
From the above results, therefore, it was found that if the composition is represented by:
X BaO.Y TiO.sub.2. Z {(Sm.sub.2 O.sub.3).sub.1-W1-W2 (La.sub.2 O.sub.3).sub.W1 (Nd .sub.2 O.sub.3).sub.W2 }.V Bi.sub.2 O.sub.3
with respect to the main constituents, where:
11.5.ltoreq.X.ltoreq.21.0
60.0.ltoreq.Y.ltoreq.76.0
6.5.ltoreq.Z.ltoreq.26.0
0.1.ltoreq.V.ltoreq.5.0
X+Y+Z+V=100
expressed in mole %, the mole ratios are specified respectively by:
0<W.sub.1 <1.0
0<W.sub.2 <1.0
0<(1-W.sub.1 -W.sub.2)<1.0,
and CeO.sub.2 is also added to the main constituents to the extent of no more than 5 wt % (excluding 0 wt %), the composition is suitable as a dielectric ceramic for microwave applications. This 5 wt % of CeO.sub.2 corresponds to 0.0606 mole of CeO.sub.2 per mole of the main constituents. The sinterability of this dielectric ceramic composition was also improved.
EXAMPLE D2
BaCO.sub.3, TiO.sub.2, Sm.sub.2 O.sub.3, La.sub.2 O.sub.3, Nd.sub.2 O.sub.3, Bi.sub.2 O.sub.3, and PbO of high purity were taken as starting materials, weighed out in the compositional proportions shown in the attached Table D1, and mixed with pure water in a pot mill. In this Example, the main constituents, i.e. BaCO.sub.3, TiO.sub.2, Sm.sub.2 O.sub.3, La.sub.2 O.sub.3, Nd.sub.2 O.sub.3 and Bi.sub.2 O.sub.3 were mixed in two different proportions, and the amount of PbO added as a supplementary constituent was varied.
This mixture was calcined in air at 1060.degree. C. for 2 hours. The calcined material was processed in the same manner as in Example B to obtain the molded circular plate. This molded product was then placed in a high purity alumina case and fired at a suitable temperature in the range 1250.degree. C. to 1400.degree. C. for 2 hours so as to obtain a dielectric ceramic.
The dielectric constant .epsilon. .sub.r and unloaded Q (Q.sub.u) of the material were measured in the same manner as in the Embodiment B, and the temperature coefficient .tau. .sub.f of the resonant frequency was found by equation (1).
The results of the experiments were shown in the attached Table D2.
According to the measurement results of Table D2, as the amount of lead oxide (PbO) is increased with respect to the main constituents, dielectric constant .epsilon. .sub.r increases up to 5 wt %, passes through a maximum of .epsilon. .sub.r =95.2, and then decreases. Unloaded Q (Q.sub.u), on the other hand, decreases with increasing addition of PbO, and falls sharply when addition exceeds 5 wt %. Further, temperature coefficient .tau. .sub.f exhibits a minimum at an addition of 3 wt %, then it begins to increase and rises sharply when addition exceeds 5 wt %. As Sample No. 6 and No. 12, have an unloaded Q (Q.sub.u) no greater than 1000 and a highly positive temperature coefficient, it is seen that they are undesirable.
From the above results, therefore, it was found that if the composition is represented by:
X BaO.Y TiO.sub.2. Z {(Sm.sub.2 O.sub.3).sub.1-W1-W2 (La.sub.2 O.sub.3).sub.W1 (Nd.sub.2 O.sub.3).sub.W2 }.V Bi.sub.2 O.sub.3
with respect to the main constituents, where:
11.5.ltoreq.X.ltoreq.21.0
60.0.ltoreq.Y.ltoreq.76.0
6.5.ltoreq.Z.ltoreq.26.0
0.1.ltoreq.V.ltoreq.5.0
X+Y+Z+V=100
expressed in mole %, the mole ratios are specified respectively by:
0<W.sub.1 <1.0
0<W.sub.2 <1.0
0<(1-W.sub.1 -W.sub.2)<1.0,
and PbO is also added to the main constituents to the extent of no more than 5 wt % (excluding 0 wt %), the composition is suitable as a dielectric ceramic for microwave applications. This 5 wt % of PbO corresponds to 0.0463 of PbO per mole of the main constituents. The sinterability of this dielectric ceramic composition was also improved.
EXAMPLE D3
BaCO.sub.3, TiO.sub.2, Sm.sub.2 O.sub.3, La.sub.2 O.sub.3, Nd.sub.2 O.sub.3, Bi.sub.2 O.sub.3 and Al.sub.2 O.sub.3 of high purity were taken as starting materials, weighed out in the compositional proportions shown in the attached Table D1, and mixed with pure water in a pot mill. In this Example, the main constituents, i.e. BaCO.sub.3, TiO.sub.2, Sm.sub.2 O.sub.3, La.sub.2 O.sub.3, Nd.sub.2 O.sub.3 and Bi.sub.2 O.sub.3 were mixed in two different proportions, and the amount of Al.sub.2 O.sub.3 added as a supplementary constituent was varied.
This mixture was calcined in air at 1060.degree. C. for 2 hours. The calcined material was processed in the same manner as in Example B to obtain the molded circular plate. This molded product was then placed in a high purity alumina case and fired at a suitable temperature in the range 1250.degree. C. to 1450.degree. C. for 2 hours so as to obtain a dielectric ceramic.
The dielectric constant .epsilon..sub.r and unloaded Q (Q.sub.u) of the material were measured in the same manner as in the Embodiment B, and the temperature coefficient .tau. .sub.f of the resonant frequency was found by equation (1).
The results of the experiments were shown in the attached Table D3.
According to the measurement results of Table D3, if the addition of aluminum oxide (Al.sub.2 O.sub.3) is no greater than 3 wt %, with respect to the main constituents, the dielectric constant .epsilon. .sub.r becomes slightly less, but it does not decrease very much. Further, if the addition is not greater than 1 wt %, unloaded Q (Q.sub.u) increases. Further, as addition of Al.sub.2 O.sub.3 increases, the temperature coefficient .tau. .sub.f goes highly negative, and it is thus possible to change the sign of the coefficient from positive to negative by adjusting the addition of Al.sub.2 O.sub.3.
If on the other hand the addition of Al.sub.2 O.sub.3 is greater than 3 wt %, i.e. in the case of Sample No. 6 and No. 12, the dielectric constant .epsilon. .sub.r is no greater than 50, the unloaded Q (Q.sub.u) decreases to 1000 or less and the temperature coefficient .tau. .sub.f goes very highly negative. It is evident that these properties are undesirable.
From the above results, therefore, it was found that if the composition is represented by:
X BaO.Y TiO.sub.2. Z {(Sm.sub.2 O.sub.3).sub.1-W1-W2 (La.sub.2 O.sub.3).sub.W1 (Nd.sub.2 O.sub.3).sub.W2 }.V Bi.sub.2 O.sub.3
with respect to the main constituents, where:
11.5.ltoreq.X.ltoreq.21.0
60.0.ltoreq.Y.ltoreq.76.0
6.5.ltoreq.Z.ltoreq.26.0
0.1.ltoreq.V.ltoreq.5.0
X+Y+Z+V=100
expressed in mole %, the mole ratios are specified respectively by:
0<W.sub.1 <1.0
0<W.sub.2 <1.0
0<(1-W.sub.1 -W.sub.2)<1.0,
and Al.sub.2 O.sub.3 is also added to the main constituents to the extent of no more than 3 wt % (excepting 0 wt %), the composition is suitable as a dielectric ceramic for microwave applications. This 3 wt % of Al.sub.2 O.sub.3 corresponds to 0.0609 mole of Al.sub.2 O.sub.3 per mole of the main constituents.
It should be understood that this invention is not limited to the Examples given in the Tables, and compositions which have different amounts of supplementary constituents within the specified range with respect to other combinations of the main constituents within the specified range, will give similar results to those of the above Examples.
As is clear from the above description of the various embodiments or examples, in the microwave region, the dielectric constant .epsilon. .sub.r and unloaded Q (Q.sub.u) of the composition of this invention are high, and furthermore, the temperature coefficient .tau. .sub.f of the resonant frequency can be varied over a wide range by varying the composition.
The composition can therefore be used as a dielectric ceramic (porcelain) for microwave resonators or for temperature compensation capacitors, and it has a high industrial value.
TABLE B1__________________________________________________________________________ X Y Z .tau..sub.fNo. (mole %) (mole %) (mole %) 1-W.sub.1 --W.sub.2 W.sub.1 W.sub.2 .epsilon..sub.r Q.sub.u (ppm/.degree.C.)__________________________________________________________________________1* 15.9 68.2 15.9 1 0 0 78.4 2,510 -1402* 15.9 68.2 15.9 0.46 0.54 0 78.1 1,694 1593 15.9 68.2 15.9 0.70 0.15 0.15 74.2 2,597 -194 15.9 68.2 15.9 0.50 0.15 0.35 76.6 2,844 215 15.9 68.2 15.9 0.30 0.15 0.55 77.9 2,902 376 15.9 68.2 15.9 0.10 0.15 0.75 78.5 2,698 827 15.9 68.2 15.9 0.50 0.35 0.15 79.1 2,464 758 15.9 68.2 15.9 0.30 0.35 0.35 78.2 2,363 999 15.9 68.2 15.9 0.40 0.05 0.55 82.4 2,348 1410 15.9 68.2 15.9 0.30 0.05 0.65 82.5 2,357 3711* 15.9 68.2 15.9 0.13 0.52 0.35 78.3 1,863 17312* 15.9 68.2 15.9 0 0.48 0.52 75.1 1,750 15413* 15.9 68.2 15.9 0 0 1 84.1 2,210 12014 16.7 66.6 16.7 0.20 0.05 0.75 83.1 2,263 5615 16.7 66.6 16.7 0.10 0.05 0.85 83.3 2,303 7216* 16.7 66.0 16.7 0.03 0 0.97 79.5 2,128 12117 19.0 75.0 6.0 0.5 0.15 0.35 72.3 2,200 4318* 25.0 72.5 2.5 0.50 0.35 0.15 51.2 1,218 10619* 9.0 71.0 20.0 0.50 0.35 0.15 55.7 1,139 14320* 18.0 50.0 32.0 0.50 0.35 0.15 54.2 872 13121 11.0 61.0 28.0 0.50 0.15 0.35 72.3 1,800 3122* 11.0 80.0 9.0 0.50 0.35 0.15 59.3 1,132 11623 22.0 60.0 18.0 0.24 0.23 0.53 58.8 1,790 74__________________________________________________________________________
TABLE B2__________________________________________________________________________ .tau..sub.fNo. X Y Z W.sub.1 W.sub.2 MnO.sub.2 .epsilon..sub.r Q.sub.u (ppm/.degree.C.)__________________________________________________________________________ 1* 19.2 67.5 13.3 0.25 0.35 0 74.5 1,852 192 19.2 67.5 13.3 0.25 0.35 0.5 75.1 2,133 153 19.2 67.5 13.3 0.25 0.35 1.5 76.6 2,427 254 19.2 67.5 13.3 0.25 0.35 3.0 75.0 2,111 47 5* 19.2 67.5 13.3 0.25 0.35 5.0 74.1 960 96__________________________________________________________________________
TABLE C1__________________________________________________________________________ Al.sub.2 O.sub.3 .tau..sub.fNo. X Y Z 1-W.sub.1 --W.sub.2 W.sub.1 W.sub.2 (wt %) .epsilon..sub.r Q.sub.u (ppm/%)__________________________________________________________________________1* 16.7 66.6 16.7 0.20 0.05 0.75 0 83.1 2260 562 " " " " " " 0.2 82.9 2410 453 " " " " " " 1 81.8 2170 154 " " " " " " 3 79.5 1950 -455* " " " " " " 10 43.1 750 -1506* 22.0 60.0 18.0 0.24 0.23 0.53 0 58.8 1790 747 " " " " " " 0.2 58.5 1920 668 " " " " " " 1 57.8 1830 239 " " " " " " 3 55.9 1630 -2110* " " " " " " 10 38.5 600 -125__________________________________________________________________________
TABLE A1__________________________________________________________________________ BaO TiO.sub.2 RE Sm.sub.2 O.sub.3 La.sub.2 O.sub.3 Nd.sub.2 O.sub.3 Bi.sub.2 O.sub.3 .tau..sub.fNO X Y Z 1-W.sub.1 --W.sub.2 W.sub.1 W.sub.2 V .epsilon..sub.r Q.sub.u (ppm/.degree.C.)__________________________________________________________________________1 15.63 66.71 15.63 0.835 0.133 0.032 2.03 77.0 2010 -862 15.63 66.71 15.63 0.624 0.122 0.254 2.03 82.2 1810 -513 15.63 66.71 15.63 0.435 0.168 0.397 2.03 85.5 1910 -354 15.63 66.71 15.63 0.281 0.196 0.423 2.03 88.1 1890 -205 15.63 66.71 15.63 0.118 0.178 0.704 2.03 91 2015 56* 14.63 68.23 14.63 0.240 0.760 0 2.51 77.5 1010 1177* 14.63 68.23 14.63 0 0.644 0.356 2.51 75.4 1205 1238 14.0 72.0 14.0 0.333 0.541 0.126 4.62 87.0 1750 599 14.0 72.0 14.0 0.180 0.470 0.350 4.62 91.4 1510 6810* 14.0 72.0 14.0 0.440 0 0.560 4.62 73.6 1770 11611* 26.5 71.5 2.0 0.340 0.280 0.380 1.05 53.1 960 11012* 11.5 84.0 4.5 0.340 0.280 0.380 1.05 51.2 1060 13613 21.0 72.5 6.5 0.340 0.280 0.380 1.05 54.2 1790 6314 21.0 60.0 19.0 0.340 0.280 0.380 1.05 68.2 1670 5115* 21.0 53.5 25.5 0.16 0.37 0.47 1.51 54.2 880 11316* 8.0 60.0 32.0 0.16 0.37 0.47 1.51 53.9 940 12117 11.5 76.0 12.5 0.16 0.37 0.47 1.51 71.3 1860 6118 12.0 60.0 26.0 0.16 0.37 0.47 1.51 73.6 1790 3319* 15.74 68.52 15.74 0.58 0.31 0.11 0 81.7 1830 5520 15.71 68.40 15.71 0.58 0.31 0.11 0.10 88.6 1860 4721 15.05 65.51 15.05 0.58 0.31 0.11 4.40 94.5 1960 1622 14.31 66.38 14.31 0.58 0.31 0.11 5.00 85.1 1570 5323* 13.12 63.76 13.12 0.58 0.31 0.11 10.00 80.9 960 115__________________________________________________________________________
TABLE A2__________________________________________________________________________ BaO TiO.sub.2 RE Sm.sub.2 O.sub.3 La.sub.2 O.sub.3 Nd.sub.2 O.sub.3 Bi.sub.2 O.sub.3 MnO.sub.2 .epsilon..sub.r Q.sub.u .tau..sub.fNO. X Y Z 1-W.sub.1 --W.sub.2 W.sub.1 W.sub.2 V O -- -- (ppm/.degree.C.)__________________________________________________________________________ 1* 18.7 68.7 10.85 0.32 0.27 0.41 1.75 0 76.3 1790 342 18.7 68.7 10.85 0.32 0.27 0.41 1.75 0.3 77.8 2065 293 18.7 68.7 10.85 0.32 0.27 0.41 1.75 1.1 78.1 2130 234 18.7 68.7 10.85 0.32 0.27 0.41 1.75 2.0 77.6 2145 31 5* 18.7 68.7 10.85 0.32 0.27 0.41 1.75 3.5 75.9 1063 77__________________________________________________________________________
TABLE D1__________________________________________________________________________ BaO TiO.sub.2 RE Sm.sub.2 O.sub.3 La.sub.2 O.sub.3 Nd.sub.2 O.sub.3 Bi.sub.2 O.sub.3 CeO.sub.2 .tau..sub.fNo. X Y Z 1-W.sub.1 --W.sub.2 W.sub.1 W.sub.2 V (wt %) .epsilon..sub.r Q.sub.u (ppm/.degree.C.)__________________________________________________________________________1* 15.63 66.71 15.63 0.281 0.296 0.423 2.03 0 88.1 1890 282 " " " " " " " 0.2 89.5 1980 213 " " " " " " " 1 87.5 2050 84 " " " " " " " 3 83.2 2310 -165 " " " " " " " 5 75.3 1950 106* " " " " " " " 10 38.1 1310 657* 14.31 66.38 14.31 0.58 0.31 0.11 5.0 0 85.1 1570 538 " " " " " " " 0.2 86.3 1630 479 " " " " " " " 1 88.6 1890 2610 " " " " " " " 3 84.7 2140 1211 " " " " " " " 5 78.3 1710 2912* " " " " " " " 10 42.6 1290 92__________________________________________________________________________
TABLE D2__________________________________________________________________________ BaO TiO.sub.2 RE Sm.sub.2 O.sub.3 La.sub.2 O.sub.3 Nd.sub.2 O.sub.3 Bi.sub.2 O.sub.3 PbO .tau..sub.fNo. X Y Z 1-W.sub.1 --W.sub.2 W.sub.1 W.sub.2 V (wt %) .epsilon..sub.r Q.sub.u (ppm/.degree.C.)__________________________________________________________________________1* 15.63 66.71 15.63 0.281 0.296 0.423 2.03 0 88.1 1890 282 " " " " " " " 0.2 88.7 1840 213 " " " " " " " 1 89.9 1780 134 " " " " " " " 3 93.5 1670 55 " " " " " " " 5 95.2 1530 206* " " " " " " " 10 82.6 820 867* 14.31 66.38 14.31 0.58 0.31 0.11 5.0 0 85.1 1570 538 " " " " " " " 0.2 86.0 1540 469 " " " " " " " 1 87.2 1490 3410 " " " " " " " 3 89.7 1440 2611 " " " " " " " 5 92.5 1380 4112* " " " " " " " 10 81.3 720 103__________________________________________________________________________
TABLE D3__________________________________________________________________________ BaO TiO.sub.2 RE Sm.sub.2 O.sub.3 La.sub.2 O.sub.3 Nd.sub.2 O.sub.3 Bi.sub.2 O.sub.3 Al.sub.2 O.sub.3 .tau..sub.fNo. X Y Z 1-W.sub.1 --W.sub.2 W.sub.1 W.sub.2 V (wt %) .epsilon..sub.r Q.sub.u (ppm/.degree.C.)__________________________________________________________________________1* 15.63 66.71 15.63 0.281 0.296 0.423 2.03 0 88.1 1890 282 " " " " " " " 0.1 87.8 1980 173 " " " " " " " 0.5 86.2 2120 64 " " " " " " " 1 84.6 1980 -135 " " " " " " " 3 78.6 1780 -396* " " " " " " " 10 46.5 920 -1187* 14.31 66.38 14.31 0.58 0.31 0.11 5.0 0 85.1 1570 538 " " " " " " " 0.1 84.9 1690 399 " " " " " " " 0.5 83.6 1830 2310 " " " " " " " 1 82.2 1660 -811 " " " " " " " 3 76.7 1510 -2812* " " " " " " " 10 39.8 710 -89__________________________________________________________________________

Claims

1. A dielectric ceramic for microwave applications consisting essentially of the components barium oxide (BaO), titanium dioxide (TiO.sub.2), samarium oxide (Sm.sub.2 O.sub.3), lanthanum oxide (La.sub.2 O.sub.3) and neodymium oxide (Nd.sub.2 O.sub.3) represented by the formula:
x BaO.Y TiO.sub.2.Z {(Sm.sub.2 O.sub.3).sub.1-W1-W2 (La.sub.2 O.sub.3).sub.W1 (Nd.sub.2 O.sub.3).sub.W2 }
where X, Y, Z lie in the ranges:
11.0.ltoreq.X.ltoreq.22.0
60.0.ltoreq.Y.ltoreq.75.0
6.0.ltoreq.Z.ltoreq.28.0
X+Y+Z=100
expressed in mole %, and
0.ltoreq.W.sub.1 .ltoreq.0.35
0<W.sub.2 <1
0<(1-W.sub.1 -W.sub.2)<1
where W.sub.1, W.sub.2 and (1-W.sub.1 -W.sub.2) are mole ratios and wherein said components are present in sufficient amounts as to produce a dielectric ceramic having a high dielectric constant, a high unloaded Q and a temperature coefficient variable above and below Oppm/.degree.C.
2. A dielectric ceramic according to claim 1 in which, MnO.sub.2 is also added, as a supplementary constituent, to the extent of no more than 3 wt %.
3. A dielectric ceramic according to claim 1 in which, Al.sub.2 O.sub.3 has also been added, as a supplementary constituent, to the extent of no more than 3 wt %, this corresponding to 0.0563 mole per mole of the main constituents.
4. A dielectric ceramic for microwave applications consisting essentially of the components barium oxide (BaO), titanium dioxide (TiO.sub.2), samarium oxide (Sm.sub.2 O.sub.3), lanthanum oxide (La.sub.2 O.sub.3), neodymium oxide (Nd.sub.2 O.sub.3) and bismuth oxide (Bi.sub.2 O.sub.3), represented by the formula:
X BaO.Y TiO.sub.2.Z {(Sm.sub.2 O.sub.3).sub.1-W1-W2 (La.sub.2 O.sub.3).sub.W1 (Nd.sub.2 O.sub.3).sub.W2 }.V Bi.sub.2 O.sub.3
where X, Y, Z and V lie in the ranges:
11.5.ltoreq.X.ltoreq.21.0
60.0.ltoreq.Y.ltoreq.76.0
6.5.ltoreq.Z.ltoreq.26.0
0.1.ltoreq.V.ltoreq.5.0
X+Y+Z+V=100
expressed in mole %, and
0<W.sub.1 <1
0<W.sub.2 <1
0<(1-W.sub.1 -W.sub.2)<1,
where W.sub.1, W.sub.2 and (1-W.sub.1 -W.sub.2) are mole ratios and wherein said components are present in sufficient amounts as to produce a dielectric ceramic having a high dielectric constant, a high unloaded Q and a temperature coefficient variable above and below 0.degree. C.
5. A dielectric ceramic according to claim 4 in which, to MnO.sub.2 is also added to the extent of no more than 2 wt %.
6. A dielectric ceramic according to claim 4, in which cerium oxide (CeO.sub.2) is also added, as a supplementary constituent, to the extent of no more than 5 wt %, this amount corresponding to 0.0606 mole per mole of the main constituents.
7. A dielectric ceramic according to claim 4 in which, to lead oxide (PbO) is also added, as a supplementary constituent, to the extent of no more than 5 wt %, this corresponding to 0.0463 mole per mole of the main constituents.
8. A dielectric ceramic according to claim 4, in which aluminum oxide (Al.sub.2 O.sub.3) is also added, as a supplementary constituent, to the extent of no more than 3 wt %, this corresponding to 0.0609 mole per mole of the main constituents.
9. A dielectric ceramic according to claim 1 in which the temperature coefficient is in the low temperature coefficient range.
10. A dielectric ceramic according to claim 4 in which the temperature coefficient is in the low temperature coefficient range.
11. A dielectric ceramic according to claim 1 in which the temperature coefficient is in the vicinity of Oppm/.degree.C.
12. A dielectric ceramic according to claim 4 in which the temperature coefficient is in the vicinity of Oppm/.degree.C.
13. A dielectric ceramic according to claim 9 in which the temperature coefficient is below Oppm/.degree.C.
14. A dielectric ceramic according to claim 10 in which the temperature coefficient is below Oppm/.degree.C.

Priority Claims (4)

Number	Date	Country
1-206566	Aug 1989	JPX
1-212641	Aug 1989	JPX
1-323226	Dec 1989	JPX
1-330677	Dec 1989	JPX

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Number	Name	Date
4330631	Kawashima et al.	May 1982
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4699891	Sato et al.	Oct 1987
4753906	Nishigaki et al.	Jun 1988
4987107	Narumi et al.	Jan 1991

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Number	Date	Country
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Entry
World Patents Index Latest Accession No. 80-85052C (Weed 48), Derwent Publications Ltd., London & JP55131901 (KCK KK) 15-01-1980.
Chemical Abstracts, vol. 107, No. 8, Aug. 24, 1987, Columbus, Ohio, U.S.A., K. Sasazawa: "Dielectric Ceramic Compositions", p. 689; left-hand column; ref. No. 69267N abstract & JP-A-6205509 (Taiyo Yuden Co., Ltd.).
Chemical Abstracts, vol. 103, No. 4, Jul. 1985, Columbus, Ohio U.S.A.,"Dielectric Ceramic Composition", p. 585; left-hand column; ref. No. 31271P & JP-A-6044905 (Matsushita Electric Industrial Co., Ltd.) abstract.
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Dielectric ceramic for microwave applications

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