Gadolinium-doped SnO2-based Varistor Materials with High Nonlinear Coefficient and Low Leakage Current
By introducing Gd into the SnO2-Co3O4-Cr2O3-Ta2O5 system,this work prepared a SnO2 varistor ceramic material with a high nonlinear coefficient and low leakage current.The results show that the doping of Gd can promote grain growth,reduce the porosity of the sample,and obtain the best electrical performance when the doping amount is 0.25mol％,with a nonlinear coefficient reaching 55 and a leakage current as low as 7.74 mA/cm2.At the same time,the voltage gradient is also as high as 568 V/mm,and the dielectric constant is as high as 213 at a frequency of 50 Hz,showing its potential application prospects.However,oversaturated doping will deteriorate the electrical properties of varistor ceramics.We attribute the change in the nonlinear coefficient to the improvement of the grain boundary barrier.The decrease in leakage current is caused by the increase in grain boundary resistance and the decrease in electron mobility.The reason for the increase in grain boundary barrier was analyzed from the perspective of point defects,and the influence mechanism of Gd doping on the electrical properties and microstructure of SnO2 varistor ceramics was systematically explained.
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