The Effect of MgO Doping on the Properties of SnO2-Based Varistor
The effects of different MgO contents on the microstructure and electrical properties of SnO2-based varistor were investigated by adopting the traditional SnO2+CoO+Nb2O5+Cr2O3 varistor system.The results show that the best electrical properties can be obtained when the MgO content is 0.5％(mole fraction),with the nonlinear coefficient of 32,the breakdown voltage gradient of 284.3 V/mm,and the leakage current density of 7.1 Μa.Because Mg2+acts as an acceptor dopant,increasing the surface state density,when the doping amount of MgO exceeds the solubility limit of the SnO2 sample,spinners are formed at the grain boundaries,which prevents the growth of ZnO grains due to the pinning effect.There-fore,the grain size is reduced and more grain boundaries are formed,which effectively improves the com-prehensive electrical properties of the SnO2 varistor.In addition,the doping of MgO makes the grain size distribution more uniform,reduces the porosity,and increases the sintered density of the samples.
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