Cermet varistors
AssigneeAllen-Bradley Company, Inc.
InventorsAllan Kouchich, George W. Taylor
Life of this patent
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Abstract
The cermet varistors have electrodes applied to an improved varistor composition which includes a semi-conductive material having zinc oxide in admixture with at least one metal oxide selected from the group consisting of chromium oxide, cobalt oxide and manganese oxide and includes a glass matrix. The glass matrix is a borosilicate glass with at least one metal oxide selected from the group consisting of cobalt oxide and manganese oxide. The improved compositions are used in varistors of both the thick film and bulk types, the resulting varistors having enhanced device characteristics, particularly high exponents of nonlinearity.
Claims10
A varistor having a nonlinear current-voltage characteristic defined by the relation
- I = (V/C).sup..alpha.
- where I is the current flowing through the varistor, V is the voltage across the varistor, C is a constant proportional to the varistor, and .alpha. is a constant >
- 1 and is a measure of the nonlinearity of the varistor, said varistor having an .alpha. value in excess of 10, comprising:
- an inert substrate;
- a thick film associated with said inert substrate comprising a varistor composition consisting essentially of from about 75.0 to about 92.0 weight percent of a semi-conductive material and from about 25.0 to about 8.0 weight percent of glass matrix;
- said semi-conductive material consisting predominantly of zinc oxide in admixture with a small amount of at least one metal oxide selected from the group consisting of chromium oxide, cobalt oxide and manganese oxide;
- said glass matrix consisting primarily of a borosilcate glass with, as an additive, at least one metal oxide selected from the group consisting of cobalt oxide and manganese oxide;
- and
- a pair of electrodes applied to said thick film.
A varistor having a nonlinear current-voltage characteristic defined by the relation
- I = (V/C).sup..alpha.
- where I is the current flowing through the varistor, V is the voltage across the varistor, C is a constant proportional to the varistor, and .alpha. is a constant >
- 1 and is a measure of the nonlinearity of the varistor, said varistor having an .alpha. value in excess of 10, comprising:
- a bonded mass of particles comprising a varistor composition consisting essentially of from about 90.0 to about 99.0 weight percent of a semi-conductive material and from about 10.0 to about 1.0 weight percent of a glass matrix;
- said semi-conductive material consisting predominantly of zinc oxide in admixture with a small amount of at least one metal oxide selected from the group consisting of chromium oxide, cobalt oxide and manganese oxide;
- said glass matrix consisting primarily of a borosilicate glass with, as an additive, at least one metal oxide selected from the group consisting of cobalt oxide and manganese oxide;
- and
- a pair of electrodes applied to said bonded mass.
Dependencies are inferred from the claim text.