Microwave Sintering and Electric Properties of ZnO Varistor Ceramics

The ZnO varistor ceramics were fabricated from ZnO powder and Ti-doped ZnO powder by microwave sintering process at 800 similar to 1150 degrees C. The effects of milling time, sintering temperature and doping on microwave sintering technique have been studied. The results show that the powder is more homogeneously and smalle with the increasing of milling time, therefore the electric properties is improved. However the particle size and the electric properties tend towards stability after 20h milling time. The density and electric properties increase with the increasing of sintering temperature, but decrease sharply at 1100 degrees C. So the better sintering temperature is 1100 degrees C. TiO2 Doping improves the electric properties of ZnO, however the electric properties decrease with more than 2.5% doping.