Barrier layer ceramic dielectric capacitor containing barium plumbate

• US 4,761,711 A
• Filed: 06/05/1987
• Issued: 08/02/1988
• Est. Priority Date: 06/05/1987
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Biggers, James V., Cross, Leslie E., Newnham, Robert E., Hiremath, Basavaraj V.
• Primary Examiner(s): GRIFFIN, DONALD
• Application Number:
  US07/058,316
• Time in Patent Office: 424 Days
• Field of Search: 252/62.3 BT, 501/136-138, 264/61, 357/10, 427/79, 427/80, 29/25.42, 361/320, 361/321
• US Class Current: 361/321.5
• CPC Class Codes: H01G 4/1281 with grain boundary layer
• CPC Class Codes: Y10T 29/435 Solid dielectric type

Abstract

A barrier layer ceramic capacitor and a method of making the same, using barium plumbate or modified barium plumbate as the base material. The fabricating process is a one step process requiring a maximum sintering temperature of 1000° C.

Claims

1. A barrier layer ceramic capacitor, comprising:

a ceramic wafer having first and second major surfaces, said wafer having a grain structure;

a first conducting layer bonded to said first major surface;

a second conducting layer bonded to said second major surface;

a glass compound diffused into the grain structure of said ceramic wafer to force a boundary layer insulator in boundary areas of said grain structure; and

wherein said ceramic wafer comprises a solid solution of modified barium plumbate having the formula;

space="preserve" listing-type="equation">Ba(Bi.sub.x Pb.sub.1-x)O.sub.3 O≦

x≦

25 mole %.

2. A barrier layer ceramic capacitor as described in claim 1, wherein said glass compound diffused into said ceramic wafer comprises a range of 4 to 0.05% by weight of said wafer after diffusion.

3. A barrier layer ceramic capacitor as described in claim 2, wherein said ceramic wafer comprises a barium plumbate ceramic.

4. A barrier layer ceramic capacitor as described in claim 1, wherein said glass compound comprises a mixture of Pb, Ga, and Bi.

5. A barrier layer ceramic capacitor as described in claim 1, wherein each said conducting layer comprises an electrode bonded to each of said first and second major surfaces by an electrode bonding means.

6. A barrier layer ceramic capacitor as described in claim 5, wherein said electrode bonding means is selected from the group consisting of:

coating, dipping, spraying, and vapor deposition.

7. A method of producing a barrier layer ceramic of modified barium plumbate comprising the steps of:

preparing a wafer of a ceramic composition having the formula;

space="preserve" listing-type="equation">Ba(Bi.sub.x Pb.sub.1-x)O.sub.3 for O≦

x≦

25 mole %;

sintering said wafer;

coating a first and a second surface of said sintered wafer with a glass compound;

diffusing said glass into the grains of a boundary layer of said first and second surfaces of said wafer; and

applying an electrode to each of said first and second surfaces of said glass coated wafer.

8. A method as described in claim 7 wherein said step of preparing a wafer of a ceramic material comprises the steps of:

milling constituents of a modified barium plumbate into a homogeneous composition;

calcining said composition in an oxidizing atmosphere;

crushing said calcined composition into a fine powder;

ballmilling said fine powder;

mixing said ballmilled powder with a resin which will serve as a binder;

drying said mixture;

sieving said mixture; and

pressing said mixture into wafer forms.

9. A method as described in claim 8, wherein said constituents comprise:

a range of 46.5 to 47 wt % BaCO₃, a range of 39.5 to 53.1 wt % PbO, and a range of 0.0 to 14 wt % Bi₂ O₃.

10. A method as described in claim 8, wherein said glass compound comprises a mixture of Pb, Bi and Ga.

11. A method as described in claim 8 wherein said step of calcining comprises heating said composition at a temperature of 600°

-1050°

C. for 8-10 hours.

12. A method as described in claim 8 wherein said step of sintering comprises:

heating said wafer to a temperature of 800°

-1000°

C. for 2-24 hours.

13. A method as described in claim 8, wherein said step of diffusing comprises heating said glass coated wafers at a temperature of 400°

-900°

C. for 5 to 70 minutes.

14. A method as described in claim 8, wherein said step of applying an electrode comprises the steps of brushing a conducting paste on said first and said second surfaces of said wafer;

and

firing said wafer at 400°

-550°

C.

15. A method as described in claim 8, wherein said step of applying an electrode is accomplished by an electrode bonding means selected from the group consisting of:

coating, dipping, spraying and vapor depositing.