Dielectric ceramic composition and laminated ceramic capacitor using the same

• US 6,243,254 B1
• Filed: 08/06/1999
• Issued: 06/05/2001
• Est. Priority Date: 08/11/1998
• Status: Expired due to Term

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Shibata, Masamitsu, Hiramatsu, Takashi, Wada, Nobuyuki, Hamaji, Yukio
• Primary Examiner(s): Dinkins, Anthony
• Application Number:
  US09/369,988
• Time in Patent Office: 669 Days
• Field of Search: 361/321.1, 361/321.2, 361/321.3, 361/321.4, 361/321.5, 361/322, 361/311-313, 501/134-139
• US Class Current: 361/311
• CPC Class Codes: C04B 35/465 based on alkaline earth metal titanates
• CPC Class Codes: C04B 35/4684 containing lead compounds C04B35/472 takes precedence
• CPC Class Codes: H01G 4/1227 based on alkaline earth titanates

Abstract

Provided is a highly reliable laminated ceramic capacitor in which decrease of dielectric constant under a high electric field is small and which satisfies the B-grade and X7R grade characteristics, using Ni for the inner electrodes, wherein the dielectric material contains about 0.2 to 5.0 parts by weight of Li₂O—(Si, Ti)₂—MO oxides (MO is at least one of the compounds of Al₂O₃ and ZrO₂) or SiO₂—TiO₂—XO oxides (XO is at least one of the compounds of BaO, CaO, SrO, MgO, ZnO and MnO) relative to 100 parts by weight of a principal component represented by (Ba_1−xCa_xO)_mTiO₂+αRe₂O₃+βMgO+γMnO (Re₂O₃ represents at least one of Y₂O₃, Gd₂O₃, Tb₂O₃, Dy₂O₃, Ho₂O₃, Er₂O₃ and Yb₂O₃).

Claims

1. A dielectric ceramic comprising

2. A dielectric ceramic according to claim 1, wherein the (Ba₁₋

xCa_xO)_mTiO₂ has a mean particle size of about 0.1 to 0.7 μ

m.

3. A dielectric ceramic according to claim 1, wherein the first sub-component is present and comprises xLiO₂—

y(Si_wTi<sub>1−

w</sub>)O₂—

zMO, x, y and z are molar percentages and 30≦

w≦

1.0, and is within the area surrounded by straight lines connecting between succeeding two points represented by A (x=20, y=80, z=0), B (x=10, y=80, z=10), C (x=10, y=70, z=20), D (x=35, y=45, z=20), E (x=45, y=45, z=10) and F (x=45, y=55, z=0) or on said lines in a ternary composition diagram having apexes represented by the components LiO₂, (Si_wTi<sub>1−

w</sub>)O₂ and MO, provided that when the first sub-component is on the line A-F, 0.3≦

w<

1.0.

4. A dielectric ceramic according to claim 3, wherein comprising at least one of Al₂O₃ and ZrO₂ in a combined amount of about 20 parts by weight or less and in which the ZrO₂ is 10 parts by weight or less relative to 100 parts by weight of the Li₂O—

(Si,Ti)O₂—

MO oxide.

5. A dielectric ceramic according to claim 3, wherein said points are A (x=0, y=20, z=80), B (x=19, y=1, z=80), C (x=49, y=1, z=50), D (x=45, y=50, z=5), E (x=20, y=75, z=5) and F (x=0, y=80, z=20) and wherein the (Ba₁₋

xCa_xO)_mTiO₂ has a mean particle size of about 0.1 to 0.7 μ

m.

6. A dielectric ceramic according to claim 1, wherein the second sub-component is present and comprises xSiO₂—

yTiO₂—

zXO, x, y and z are molar percentages, and is within the area surrounded by straight lines connecting between succeeding two points represented by A (x=85, y=1, z=14), B (x=35, y=51, z=14), C (x=30, y=20, z=50) and D (x=39, y=1, z=60) or on said lines in a ternary composition diagram having apexes represented by the components SiO₂, TiO₂ and XO.

7. A dielectric ceramic according to claim 6, comprising at least one of Al₂O₃ and ZrO₂ in a combined amount of about 15 parts by weight or less and the ZrO₂ is 5 parts by weight or less relative to 100 parts by weight of the SiO₂—

TiO₂—

XO oxide.

8. A dielectric ceramic according to claim 6, wherein said points are A (x=1, y=14, z=85), B (x=20, y=10, z=70), C (x=30, y=20, z=50), D (x=40, y=50, z=10), E (x=20, y=70, z=10) and F (x=1, y=39, z=60) and wherein the (Ba₁₋

xCa_xO)_mTiO₂ has a mean particle size of about 0.1 to 0.7 μ

m.

9. A dielectric ceramic according to claim 1 in which the third sub-component is present.

10. A dielectric ceramic according to claim 2, wherein the molar ratio of (Ba+Ca)/Ti is about 0.99 to 1.035.

11. A laminated ceramic capacitor having:

a plurality of dielectric layers containing the dielectric ceramic according to claim 1;

a plurality of inner dielectric layers comprising Ni or a Ni alloy and existing among a plurality of said dielectric layers; and

external electrodes in electrical continuity to a plurality of said inner dielectric layers and being on the surface of said ceramic capacitor.

12. A laminated ceramic capacitor according to claim 11, wherein said external electrodes comprise a sintered layer of conductive metal powder or conductive metal powder and glass frit.

13. A laminated ceramic capacitor having:

a plurality of dielectric layers containing the dielectric ceramic according to claim 2;

a plurality of inner dielectric layers comprising Ni or a Ni alloy and existing among a plurality of said dielectric layers; and

external electrodes in electrical continuity to a plurality of said inner dielectric layers and being on the surface of said ceramic capacitor.

14. A laminated ceramic capacitor according to claim 13, wherein said external electrodes comprise a sintered layer of conductive metal powder or conductive metal powder and glass frit.

15. A laminated ceramic capacitor having:

a plurality of dielectric layers containing the dielectric ceramic according to claim 3;

a plurality of inner dielectric layers comprising Ni or a Ni alloy and existing among a plurality of said dielectric layers; and

external electrodes in electrical continuity to a plurality of said inner dielectric layers and being on the surface of said ceramic capacitor.

16. A laminated ceramic capacitor according to claim 15, wherein said external electrodes comprise a sintered layer of conductive metal powder or conductive metal powder and glass frit.

17. A laminated ceramic capacitor having:

a plurality of dielectric layers containing the dielectric ceramic according to claim 6;

a plurality of inner dielectric layers comprising Ni or a Ni alloy and existing among a plurality of said dielectric layers; and

external electrodes in electrical continuity to a plurality of said inner dielectric layers and being on the surface of said ceramic capacitor.

18. A laminated ceramic capacitor according to claim 17, wherein said external electrodes comprise a sintered layer of conductive metal powder or conductive metal powder and glass frit.

19. A laminated ceramic capacitor having:

a plurality of dielectric layers containing the dielectric ceramic according to claim 9;

a plurality of inner dielectric layers comprising Ni or a Ni alloy and existing among a plurality of said dielectric layers; and

external electrodes in electrical continuity to a plurality of said inner dielectric layers and being on the surface of said ceramic capacitor.

20. A laminated ceramic capacitor according to claim 19, wherein said external electrodes comprise a sintered layer of conductive metal powder or conductive metal powder and glass frit.