Flash sintering preparation and electrical properties of ZnO-Bi₂O₃-M (M = Cr₂O₃, MnO₂ or Co₂O₃) varistor ceramics

The dense bulk ZnO-Bi2O3 based varistor ceramics were obtained via flash sintering at a low temperature. The effect of different additives such as Cr2O3, MnO2 and Co2O3 on flash sintering onset temperature and incubation time was investigated. All samples were fabricated under a constant heating rate with a DC electric field of 300 V/cm. At the same time, the onset temperature of all samples was below 750 degrees C. ZnO-Bi2O3-Cr2O3 was fabricated at the lowest temperature of 704 degrees C and the shortest incubation time among the specimens by a constant heating rate flash sintering. In addition, the nonlinear current-voltage and dielectric properties were analyzed. ZnO-Bi2O3-Co2O3 varistor ceramics showed the highest nonlinear coefficient of 39.5 and the lowest leakage current of 2.64 mu A. Therefore, flash sintering is a promising method for preparation of ZnO varistor ceramics efficiently.