Method of forming a glass-reacted-ceramic with cadmium
AssigneeSprague Electric Company
InventorGaleb H. Maher
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Abstract
A method for forming a cadmium-containing glass-reacted-ceramic body is described. This material is advantageously employed as the dielectric material in a capacitor. The method comprises mixing a barium-titanate alkaline-earth-metal-zirconate powder with glass powder, forming a cake or layer of the powder mix and firing the cake at from 1600.degree. to 2050.degree. F in a controlled cadmium containing atmosphere to sinter and densify the material. The cake is buried in an inert powder to which has been added a cadmium oxide powder to supply a source of cadmium external of the cake and to control the cadmium containing atmosphere during firing. Cadmium ions diffuse, during sintering, into the glass and further, into the ceramic grains to promote grain growth and to downwardly shift the Curie temperature.
Claims12
A method for making a glass-reacted-ceramic body comprising mixing a major proportion of a finely ground ceramic comprised of barium titanate and an alkaline-earth-metal zirconate and a minor proportion of a pulverized low temperature glass;
- forming a cake of said mixture;
- placing a quantity of cadmium oxide powder adjacent to said cake;
- and firing said cake and said cadmium oxide powder at a temperature of between 1600.degree. F to 2050.degree. F so that said cadmium oxide powder provides during said firing a controlled and enriched cadmium atmosphere external of said cake to transform said cake during said firing into a sintered body and to cause cadmium ions from said cadmium of said atmosphere to react with said ceramic and to diffuse into the titanate lattice thereof, whereby grain growth in said body is enhanced and the Curie temperature of said body is shifted downwardly.
A method for making a glass-reacted-ceramic body comprising mixing a major proportion of a finely ground ceramic comprised of barium titanate and an alkaline-earth-metal zirconate and a minor proportion of a pulverized low temperature glass;
- forming layers of said glass-ceramic mixture;
- coating said layers with an electroding paste, stacking said electroded layers to form a cake;
- placing a quantity of cadmium oxide powder adjacent to said cake;
- and firing said cake and said cadmium oxide powder at a temperature of between 1600.degree. and 2050.degree. F so that said cadmium oxide powder provides during said firing a controlled and enriched cadmium atmosphere external of said cake to transform said cake during said firing into a sintered body and to cause cadmium ions from said cadmium of said atmosphere to react with said ceramic and to diffuse into the titanate lattice thereof.
Dependencies are inferred from the claim text.