Metal oxide varistors typically are made by bulk ceramic technology. The ho
mogeneity of ceramics and the grain interface profile are of primary concer
n in varistor design and processing. The nonohmic property in the ZnO varis
tor is attributed to the Bi enrichment at ZnO grain boundaries and Bi-rich
intergranular layer. The Bi susceptibility for formation of agglomerates an
d volatilization during varistor sintering is a problem. To overcome it, we
decided to pre-react Bi2O3 with Ba and add the varistor mixture with BaBiO
2.77 instead of Bi2O3 AS it appeared, BaBiO2.77 addition benefits varistor
ceramics in many ways. Varistors have better electrical properties. The ori
gin of nonohmic behaviour takes place at a lower temperature, 1100 instead
of 1250 degreesC. The Bi phase distribution in the ceramics is homogenous.
Also, the volume of not contributing with break-down voltage intergranular
phase is restrained. Taking into account that due to it the amount of addit
ives decrease and that at lower sintering temperature, less volatile Bi is
liberated to ambient, BaBiO2.77 addition benefits varistors not only techno
logically but also from the point of view of economics and environment prot
ection. (C) 2001 Published by Elsevier Science Ltd.