High voltage gradient and low residual-voltage ZnO varistor ceramics tailored by doping with In2O3 and Al2O3

Abstract This study determined the effect of indium doping on the electrical properties of Al-doped ZnO varistors. Scanning electron microscopy, current-voltage testing in a range from small to large current, capacitance-voltage testing, and X-ray diffraction pattern testing were carried out. The results show that both the voltage gradient and nonlinear coefficient of sintered ZnO varistors increase and then decrease with increasing indium dopant at a given aluminum content. Meanwhile, the leakage current and residual voltage ratio show an inverse relationship. The varistor ceramic with 0.015 mol% indium and 0.02 mol% aluminum has optimal performance. This work is helpful for improving the protective effects of ZnO varistors and increasing the safety of electrical systems.