Influence Mechanism of Formulation System and Sintering Process on Macroscopic Proper-ties of ZnO Varistors
ZnO varistor is the core component of metal oxide surge arrester,which plays a crucial role in suppressing overvoltage in transmission and distribution system.Optimizing the multivariate regulation technology and improving the sintering process are important means to develop high-performance varistors.At present,the systematic scientific research on the mechanism of its influence on the microstructure and macroscopic performance of varistors is rarely available in the literature.In order to address this problem,we experimentally performed the study and obtained the effects of differ-ent Y3+,Bi3+,Al3+contents and sintering temperatures on the average grain size S,grain inhomogeneities σg,voltage gradiant E1mA,non-linear coefficient α1mA,and leakage current IL of varistors,and established a Voronoi network model of varistor to obtain the characteristics of the changes in the macroelectrical properties.The experimental and computational results show that the addition of Y3+in the arrester can substantially improve E1mA,but facilitates α1mA and IL to deterio-rate,and reduces the working stability.The α1mA and IL values show U-shaped changes with the sintering temperature and Bi concentration.The best performance is achieved at the sintering temperature of 1100℃and the content of Bi of 1 mol%.The introduction of Al3+helps to improve the working stability,but facilitates E1mA,α1mA and IL to deteriorate.Op-timizing the process method to increase the proportion of Al3+solidly dissolved into the grains can reduce the macroscopic performance degradation.The results can provide important theoretical and experimental bases for the development of high-performance varistors.
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