Thick film ZnO based varistors prepared by screen printing

Abstract

Thick film varistors based on the system ZnO–Bi 2O 3–Sb 2O 3 have been prepared by screen printing technology on dense alumina substrates. Different processing strategies have been designed in order to control the excessive volatilization of Bi 2O 3 in varistor films during the sintering, due to the high area–volume ratio, and as a means to improving their electrical response. Starting powders were selected and pre-treated in different ways to obtain different phases and control the Bi-rich liquid phase formation. Significant differences have been observed in the electrical properties which are related to the selection of the starting powders.