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

Abstract 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 °C. ZnO–Bi2O3–Cr2O3 was fabricated at the lowest temperature of 704 °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 μA. Therefore, flash sintering is a promising method for preparation of ZnO varistor ceramics efficiently.