The Grain Growth Control of ZnO-V(2)O(5) Based Varistors by PrMnO(3) Addition

In this study, the grain growth behaviour of ZnO-V(2)O(5)-based ceramics with 0.25–0.75 mol% additions of PrMnO(3) was systematically investigated during sintering from 850 °C to 925 °C. with the aim to control the ZnO grain size for their application as varistors. It was found that with the increased addition of PrMnO(3), in addition to the decrease in the average grain size, the grain size distribution also narrowed and eventually changed from a bimodal to unimodal distribution after a 0.75 mol% PrMnO(3) addition. The grain growth control was achieved by a pinning effect of the secondary ZnCr(2)O(4) and PrVO(4) phases at the ZnO grain boundaries. The apparent activation energy of the ZnO grain growth in these ceramics was found to increase with increased additions of PrVO(4), hence the observed reduction in the ZnO grain sizes.