Improvement in Impact Stability of ZnO Varistors through Donor Doping

The effects of aluminum indium codoping on the microstructure and electrical properties of ZnO varistors, especially the surge impact stability, were studied. The microstructure was characterized by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrical properties were evaluated by using current-voltage test, pulsed current impulse test and capacitance-voltage test. The sample doped with 0.0008 mol% Al³⁺ and 0.0033 mol% In³⁺ exhibited excellent electrical properties, with breakdown voltage gradient of 95.3 V·mm⁻¹, nonlinear coefficient of 74 and residual voltage ratio of 2.43. In addition, after 20 shocks at 8/20 μs 10 kA current, the positive and negative voltage change rates were +3.30% and −6.67%, respectively.