Zinc oxide ceramics and method for producing the same and zinc o

Details Zinc oxide ceramics and method for producing the same and zinc o Zinc oxide ceramics and method for producing the same and zinc o

1996-08-29

1998-04-14

Tso, Edward

Electrical resistors

Resistance value responsive to a condition

Current and/or voltage

264617, H01C 710, H01C 713

Patent

active

057397422

ABSTRACT:
A zinc oxide ceramic and a method for producing the zinc oxide ceramics are provided wherein a zinc oxide varistor for a high voltage which has excellent electric characteristics and great reliability for DC loading and surge can be produced in high yield by performing sintering at a temperature of 750.degree. to 1050.degree. C. At least one of B.sub.2 O.sub.3, Cr.sub.2 O.sub.3, GeO.sub.2, LaO.sub.3, MgO, Nb.sub.2 O.sub.5, Nd.sub.2 O.sub.3, PbO, PrO, Sb.sub.2 O.sub.3, SiO.sub.2, SnO.sub.2, Ta.sub.2 O.sub.5, WO.sub.3 and Y.sub.2 O.sub.3 powders and a Bi.sub.2 O.sub.3 powder are mixed. A mixture thus obtained is heat treated at a temperature of 400.degree. to 700.degree. C. and ground to prepare a synthetic powder. 0.5 to 20 parts by weight of the synthetic powder and 0.1 to 5.0 parts by weight of at least one of CoO, MnO.sub.2 and NiO powders are added and ground for 100 parts by weight of a zinc oxide powder. A binder is added to the ground powder to form a sheet. A silver paste is applied to the surface of the sheet to laminate four sheets. A lamination is integrally sintered at a temperature of 840.degree. C. A zinc oxide varistor of a lamination type comprises an internal silver electrode, an internal silver counter electrode, an effective layer, a noneffective layer, and an external silver electrode.

REFERENCES:
patent: 4111852 (1978-09-01), Ho et al.
patent: 4180483 (1979-12-01), Ho et al.
patent: 5004573 (1991-04-01), Oh et al.
Matsuoka, "Nonohmic Properties of Zinc Oxide Ceramic" Japanese Journal of Applied Physics, vol. 10, No. 6, pp. 736-746, Jun. 1971.
Chen et al., "Grain Growth Processes in Zno Varistors with Various Velence States of Manganese and Cobalt" Journal of Applied Physics, 69, pp. 8363-8367, Jun. 1991.

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