Non-reducing dielectric ceramic, monolithic ceramic capacitor using the same, and method for making non-reducing dielectric ceramic
First Claim
1. A monolithic ceramic capacitor comprising:
- at least three dielectric ceramic layers;
at least one pair of internal electrodes each of which is disposed between a different pair of dielectric ceramic layers;
a pair of external electrodes, each of which is electrically connected to a different one of said pair of internal electrodes;
wherein the dielectric ceramic layers comprise a non-reducing dielectric ceramic comprising Ca, Zr and Ti as metallic elements, free of Pb, and having a perovskite primary crystal phase and other crystal phases;
wherein the ratio of the maximum peak intensity of secondary crystal phases to the maximum peak intensity at 2θ
=25°
to 35°
of the perovskite primary crystal phase in a CuKα
X-ray diffraction pattern is about 12% or less, wherein the secondary crystal phases include all the crystal phases other than the perovskite primary crystal phase; and
wherein the internal electrodes comprise a base metal.
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Abstract
A non-reducing dielectric ceramic contains Ca, Zr and Ti as metallic elements and does not contain Pb. In a CuKα X-ray diffraction pattern, the ratio of the maximum peak intensity of secondary crystal phases to the maximum peak intensity at 2θ=25° to 35° of a perovskite primary crystal phase is about 12% or less, the secondary crystal phases including all the crystal phases other than the perovskite primary crystal phase. The non-reducing dielectric ceramic exhibits superior insulating resistance and dielectric loss after firing in a neutral or reducing atmosphere and high reliability in a high-temperature loading lifetime test and is useful for producing compact high-capacitance monolithic ceramic capacitors.
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Citations
16 Claims
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1. A monolithic ceramic capacitor comprising:
-
at least three dielectric ceramic layers;
at least one pair of internal electrodes each of which is disposed between a different pair of dielectric ceramic layers;
a pair of external electrodes, each of which is electrically connected to a different one of said pair of internal electrodes;
wherein the dielectric ceramic layers comprise a non-reducing dielectric ceramic comprising Ca, Zr and Ti as metallic elements, free of Pb, and having a perovskite primary crystal phase and other crystal phases;
wherein the ratio of the maximum peak intensity of secondary crystal phases to the maximum peak intensity at 2θ
=25°
to 35°
of the perovskite primary crystal phase in a CuKα
X-ray diffraction pattern is about 12% or less, wherein the secondary crystal phases include all the crystal phases other than the perovskite primary crystal phase; and
wherein the internal electrodes comprise a base metal. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for making a non-reducing dielectric ceramic comprising Ca, Zr and Ti as metallic elements, free of Pb, and having a ratio of the maximum peak intensity of secondary crystal phases to the maximum peak intensity at 20=25°
- to 35°
of a perovskite primary crystal phase in a CuKα
X-ray diffraction pattern of about 12% or less, wherein the secondary crystal phases include all the crystal phases other than the perovskite primary crystal phase, the method comprising the steps of;(A) providing a calcined powder for providing the B-site component of a dielectric ceramic represented by the general formula ApBO3;
(B) providing powder for providing the A-site component;
(C) mixing the calcined B-site component powder and the A-site component powder to prepare an uncalcined primary material powder;
(D) calcining the uncalcined primary material powder to prepare a calcined primary material powder;
(E) adjusting the composition of the calcined primary material powder to realize the desired value of p by adding at least one of the A-site component powder and B-site component powder to the calcined primary material powder to prepare a secondary material powder; and
(F) molding and sintering the secondary material powder under a neutral or reducing atmosphere. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16)
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14. A method for making a non-reducing dielectric ceramic according to claim 13, wherein the secondary material powder is a ceramic powder having a composition represented by (Ca1-v-wSrvBaw)p(Zr1-x-yTixHfy)O3, and wherein p is adjusted to a value of about 0.98 to 1.02.
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15. A method for making a non-reducing dielectric ceramic according to claim 14, wherein p is adjusted to a value of about 0.98 to 1.02.
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16. A method for making a non-reducing dielectric ceramic according to claim 15, wherein the B-site component powder which is calcined has an average particle diameter of about 0.5 μ
- m or less.
- to 35°
Specification