Reduction-resistant dielectric ceramic compact and laminated ceramic capacitor

• US 6,522,521 B2
• Filed: 07/31/2001
• Issued: 02/18/2003
• Est. Priority Date: 07/31/2000
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Miki, Hisashi, Mizuno, Shinobu, Sano, Harunobu
• Primary Examiner(s): Reichard, Dean A.
• Assistant Examiner(s): Ha, Nguyen T
• Application Number:
  US09/919,409
• Publication Number:
  US 20020039272A1
• Time in Patent Office: 567 Days
• Field of Search: 361/321.4, 361/320, 361/321.1, 361/321.2, 361/321.3, 361/321.5, 361/311, 361/313, 361/306.3, 361/321, 361/309, 501/137, 501/138, 501/139
• US Class Current: 361/321.4
• CPC Class Codes: C04B 35/4682 based on BaTiO3 perovskite phase
• CPC Class Codes: H01G 4/1227 based on alkaline earth titanates
• CPC Class Codes: H01G 4/232 electrically connecting two or more layers of a stacked or rolled capacitor

Abstract

A dielectric ceramic compact is provided which can decrease loss and heat generation under high frequency and high voltage or large current conditions, which exhibits a stable insulating resistance by AC or DC loading, and which can form a laminated ceramic capacitor using nickel or the like as an internal electrode material. The reduction-resistant dielectric ceramic compact is formed of an auxiliary sintering agent and a solid solution containing barium titanate as a primary component represented by the formula ABO₃+aR+bM, where R is a compound containing an element such as La, and M is a compound containing an element such as Mn. In addition, 1.000<A/B≦1.035, 0.005≦a≦0.12, and 0.005≦b≦0.12. Furthermore, in the ceramic, the crystalline axis ratio c/a obtained by x-ray diffraction in a temperature range of −25° C. or above satisfies 1.000≦c/a≦1.003, and in temperature dependence of relative dielectric constant measured at an electric field of 2 Vrms/mm or less and at a frequency of 1 kHz, the maximum peak is present at a temperature of below −25° C.

Claims

1. A reduction-resistant dielectric ceramic compact comprising:

a solid solution comprising barium titanate as a primary component and an auxiliary sintering agent which has an x-ray diffraction crystalline axis ratio c/a in a temperature range of −

25°

C. or above of 1.000≦

c/a≦

1.003 and a maximum peak for temperature dependence of a dielectric constant measured at an electric strength of 2 Vrms/mm or less and at an AC frequency of 1 kHz at a temperature of below −

25°

C.,

wherein the primary component is represented by the formula

2. A reduction-resistant dielectric ceramic compact according to claim 1, wherein the auxiliary sintering agent is about 0.2 to 4 parts by weight with respect to 100 parts by weight of the primary component.

3. A reduction-resistant dielectric ceramic compact according to claim 1, wherein the primary component comprises X(Zr,Hf)O₃ in which X is at least one element selected from the group consisting of Ba, Sr and Ca.

4. A reduction-resistant dielectric ceramic compact according to claim 3, wherein the amount of X(Zr,Hf)O₃ is greater than zero up to about 0.20 mole with respect to 1 mole of the ABO₃ in the primary component.

5. A reduction-resistant dielectric ceramic compact according to claim 1, wherein the primary component further comprises a compound D containing at least one element selected from the group consisting of V, Nb, Ta, Mo, W, Y, Sc, P, Al and Fe.

6. A reduction-resistant dielectric ceramic compact according to claim 5, wherein the amount of D is more than zero up to about 0.02 mole with respect to 1 mole of the ABO₃ in the primary component.

7. A reduction-resistant dielectric ceramic compact according to claim 5, wherein the primary component comprises X(Zr,Hf)O₃ in which X is at least one element selected from the group consisting of Ba, Sr and Ca.

8. A reduction-resistant dielectric ceramic compact according to claim 3, wherein the amount of X(Zr,Hf)O₃ and the amount of D are each greater than zero up to about 0.20 mole with respect to 1 mole of the ABO₃ in the primary component.

9. A reduction-resistant dielectric ceramic compact according to claim 8, wherein

ABO₃ is a barium titanate-based perovskite compound represented by the formula {(Ba_1-x-ySr_xCa_y)O}_mTiO₂ in which 0≦

x+y≦

0.20 and 1.000<

m≦

1.035, and the auxiliary sintering agent is selected from the group consisting of a compound containing boron, a compound containing silicon and a compound containing boron and silicon, and

which further comprises, with respect to 100 parts by weight of the barium titanate-based perovskite compound, a positive amount up to about 0.5 part of a compound containing at least one element selected from the group consisting of S, Na and K, and a positive amount up to about 5 parts of a compound containing Cl.

10. A reduction-resistant dielectric ceramic compact according to claim 1, wherein

ABO₃ is a barium titanate-based perovskite compound represented by the formula {(Ba_1-x-ySr_xCa_y)O}_mTiO₂ in which 0≦

x+y≦

0.20 and 1.000<

m≦

1.035, and

further comprises, with respect to 100 parts by weight of the barium titanate-based perovskite compound, a positive amount up to about 0.5 part of a compound containing at least one element selected from the group consisting of S, Na and K, and a positive amount up to about 5 parts of a compound containing Cl.

11. A reduction-resistant dielectric ceramic compact according to claim 1, wherein the auxiliary sintering agent is selected from the group consisting of a compound containing boron, a compound containing silicon and a compound containing boron and silicon.

12. A reduction-resistant dielectric ceramic compact according to claim 11, wherein the compound containing silicon is silicon oxide.

13. A laminated ceramic capacitor comprising:

a plurality of dielectric ceramic layers;

a plurality of internal electrodes each of which sandwiches at least a part of a dielectric ceramic layer; and

a pair of external electrodes electrically connected to the internal electrodes,

wherein the dielectric ceramic layers comprise a reduction-resistant dielectric ceramic compact according to claim 9.

14. A laminated ceramic capacitor according to claim 13, wherein the internal electrodes comprise nickel, a nickel alloy, copper or a copper alloy.

15. A laminated ceramic capacitor according to claim 14, wherein each external electrodes comprises a first sintered layer comprising a powdered conductive metal and optionally glass frit, crystallized glass or ceramic;

and a second layer disposed on the first layer and which is a plating layer.

16. A laminated ceramic capacitor comprising:

a plurality of dielectric ceramic layers;

a plurality of internal electrodes each of which sandwiches at least a part of a dielectric ceramic layer; and

a pair of external electrodes electrically connected to the internal electrodes,

wherein the dielectric ceramic layers comprise a reduction-resistant dielectric ceramic compact according to claim 7.

17. A laminated ceramic capacitor according to claim 16, wherein the internal electrodes comprise nickel, a nickel alloy, copper or a copper alloy.

18. A laminated ceramic capacitor according to claim 17, wherein each external electrodes comprises a first sintered layer comprising a powdered conductive metal and optionally glass frit, crystallized glass or ceramic;

and a second layer disposed on the first layer and which is a plating layer.

19. A laminated ceramic capacitor comprising:

a plurality of dielectric ceramic layers;

a plurality of internal electrodes each of which sandwiches at least a part of a dielectric ceramic layer; and

a pair of external electrodes electrically connected to the internal electrodes,

wherein the dielectric ceramic layers comprise a reduction-resistant dielectric ceramic compact according to claim 1.

20. A laminated ceramic capacitor according to claim 19, wherein the internal electrodes comprise nickel, a nickel alloy, copper or a copper alloy.

21. A laminated ceramic capacitor according to claim 19, wherein each external electrodes comprises a first sintered layer comprising a powdered conductive metal and optionally glass frit, crystallized glass or ceramic;

and a second layer disposed on the first layer and which is a plating layer.