Effects of In2O3 and Ta2O5 co-doping on microstructure and electrical properties of ZnO low-voltage varistor

In this work, ZnO-Bi2O3 based low-voltage varistors were prepared by co-doping of In2O3 and Ta2O5, which achieved a high nonlinear coefficient with a low breakdown voltage. By exploring the microstructure and electrical performance of the samples, it was found that the samples co-doped with In2O3 and Ta2O5 have uniform microstructure, and the threshold voltage decreased slightly while the leakage current decreased. The best performance of the varistor was obtained at 0.15 mol% Ta2O5 doping with a breakdown voltage of 184 V/mm, a nonlinear coefficient of 32.3 and a leakage current of 0.04 mu A. The grain boundary resistance of the varistor increased after the co-doping of In2O3 and Ta2O5, which was conducive to improving performance stability of the sample. All varistors could be aged, but the parameter change rate of doped varistors was significantly smaller.