Effect of additive particle size on degradation behavior of ZnO varistors under high current surges

The impact of the additive particle size on the electrical properties, particularly the degradation behaviors of ZnO varistors under high current surges, was comprehensively explored. The particle size distribution of the additives was examined by analyzing particle size distribution curves. Additionally, the grain size distribution of the ZnO varistors was observed using scanning electron microscopy and fitted with the log-normal probability density function. The results indicated that the optimal average additive particle size was 256 nm, which exhibited the most uniform grain size distribution and the best degradation behaviors of the ZnO varistors under high current surges. The deviations of the forward and the backward breakdown voltage gradients were − 5.24% and − 1.43%, respectively. The current distribution of the varistors was simulated using a Voronoi network and the finite element method. The results revealed that the varistors made from the additive with particle size of 256 nm exhibited a uniform current distribution, which is beneficial for the stable degradation behavior.