Fabrication of high-field zinc oxide varistors by sol-gel processing

Advanced ceramic processing techniques were used to fabricate ZnO varistors having grain sizes in the 3 to 4 ..mu..m range, compared to 7 to 13 ..mu..m in commercial devices. The fine-grained varistors exhibited high breakdown fields, compared to commercial materials. Processing steps included synthesis of highly active powders by sol-gel techniques and hot pressing at temperatures below about 800/sup 0/C in a reducing environment to achieve high density. Heat treatment in air at temperatures up to 1000/sup 0/C fully developed the nonohmic electrical properties. 13 references, 6 figures, 4 tables.