Abstract
The doping effect of Fe 2O 3 on the microstructural and electrical properties of ZnO–Pr 6O 11 based varistor ceramic materials was investigated. Fe 2O 3 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 Fe 2O 3 increased from 0 to 1 mol%. When the doping level of Fe 2O 3 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 Fe 2O 3, more Fe atoms would segregate at grain boundaries, providing more extra electrical carriers, decreasing the resistances of the grain boundaries, and PrFeO 3 would be formed, destroying the construction of grain boundaries. Therefore, the nonlinear electrical properties of the resultant varistor materials were deteriorated.
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