Enhanced voltage gradient and energy absorption capability in ZnO varistor ceramics by using nano-sized ZnO powders

In the present study, both enhanced voltage gradient of 803 V/mm and superior energy absorption capability of 400 J/cm³ were achieved in ZnO varistors prepared by nano-sized raw powders. Further analysis indicated that such improvement could be ascribed to the refined micromorphology. As shown by SEM pictures, the average grain size was dramatically decreased by the nano-sized powders, which contributed to the enhanced voltage gradient. Meanwhile, the homogeneous grain size distribution resulted in the improved energy absorption capability. The improved varistors in the present study showed high potential for ultra-high voltage applications. In addition, we proposed an effective approach to quantitatively evaluate the grain size distribution, which is the key parameter for the electrical properties of the varistors. It provided a guideline for further modifications on wide range of electronic ceramics.