Thick film ZnO based varistors prepared by screen printing

Thick film varistors based on the system ZnO–Bi2O3–Sb2O3 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 Bi2O3 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.