Effects of Y2O3 and In2O3 on the electrical properties of SnO2-based varistors

The effects of Y2O3 and In2O3 on the microstructure and electrical properties of SnO2-based varistors were investigated. It was observed that the grain size of the samples decreased with doping Y2O3 and In2O3 and accordingly, the breakdown electrical field E-B increased greatly. The measurements of barrier height phi(B) and grain size reveal that the variation of grain size was not the only reason for the change of electrical properties of the sample doped with In2O3 and, the improvement of nonlinear coefficient a may mainly attribute to the increase of barrier height. Some energy levels of different state defects on the grain boundary were obtained and the energy about 0.15 eV detected here of all the samples may be attributed to the activation of Sn-i(x+). The different effects of doping Y2O3 and In2O3 indicate that In2O3 is more effective to improve nonlinear electrical behavior and breakdown electrical field of SnO2-based varistors.