Influence of Fe2O3 doping on microstructural and electrical properties of ZnO–Pr6O11 based varistor ceramic materials

The doping effect of Fe2O3 on the microstructural and electrical properties of ZnO–Pr6O11 based varistor ceramic materials was investigated. Fe2O3 doping would inhibit the growth of ZnO grains, whose average sizes were found to decrease from 3.0 to 2.7 μm with the doping level of Fe2O3 increased from 0 to 1 mol%. When the doping level of Fe2O3 was 0.005 mol%, the varistors exhibited the optimum nonlinear electrical characteristics with nonlinear coefficient of about 26, breakdown voltage of approximately 571 V/mm and leakage current of less than 65 μA. With higher doping level of Fe2O3, more Fe atoms would segregate at grain boundaries, providing more extra electrical carriers, decreasing the resistances of the grain boundaries, and PrFeO3 would be formed, destroying the construction of grain boundaries. Therefore, the nonlinear electrical properties of the resultant varistor materials were deteriorated.

Research highlights▶ ZnO–Pr6O11 based varistor ceramic materials. ▶ Eliminating the few drawbacks due to the high volatility and reactivity of Bi2O3 during liquid sintering by Pr6O11 substituting Bi2O3. ▶ Optimizing doping of Fe2O3 in ZnO–Pr6O11 based varistor ceramic materials.