Microstructure and Electrical Properties of In2O3, La2O3 and Ga2O3 Doped ZnO-Bi2O3-MnO2-SiO2-TiO2 Varistor Ceramics

ZnO-Bi2O3-MnO2-SiO2-TiO2 varistor ceramics with addition of X2O3 (X = In, La, Ga) were manufactured through the conventional solid-state method and their phase transformation, microstructure, band gap, and electrical properties were investigated by X-ray diffractometer, Scanning electron microscopy, Fourier transform infrared spectroscopy, and solid UV absorption spectrometry, respectively. The results show that ZnO-Bi2O3-MnO2-SiO2-TiO2-0.15 mol% X2O3 ceramics can be successfully produced at a very low temperature of 875 °C. When X2O3, especially Ga2O3, is doped into ZnO varistors, the grain sizes of specimens are refined. The grain size of ZnO-based varistor ceramics with Ga2O3 doping decreases obviously from 4.31 to 3.10 μm, and the voltage gradient increases from 763.1 to 1047.5 V mm−1. The nonlinear coefficient of ZnO-based varistor ceramics with In2O3 doping increases from 26.5 to 36.7.