A unique tuning effect of Mg on grain boundaries and grains of ZnO varistor ceramics

The effect of Mg doping on the structure and the comprehensive electrical properties of the ZnO varistors were systematically studied by comparing the doping methods of soluble salt and metal oxide. For the first time, we found that Mg as a neutral doping element could not only improve the nonlinearity but also decreased the residual voltage ratio, due to the unique tuning effect of Mg on the grain boundaries and the grains of the ZnO varistors. By appropriate Mg doping, the varistor showed excellent comprehensive electrical performance with breakdown voltage gradient of 197.1 V mm(-1), nonlinear coefficient of 88.4, leakage current of 0.8 mu A, residual voltage ratio of 1.68 under 5 kA 8/20 mu s surges, current carrying capacity of 18 shocks of 2 ms rectangular impulse current of 400 A, and the minimum power loss of 0.15 W at 135 degrees C under 85 % U-1mA/root 2 AC voltage.

Automated summary

Magnesium doping has a significant impact on the comprehensive electrical properties of ZnO varistors, improving nonlinearity, decreasing residual voltage ratio, and exhibiting excellent overall electrical performance.