Densification and Surge Current Performance of SnO_2-Sb_2O_3 Based Varistor Ceramics

Influence of TiO2,Co3O4,Cr2O3,Ni2O3 and MnO dopings on the microstructure and electrical properties of SnO2-Sb2O3 based varistor ceramic materials was investigated. It is found that TiO2 and Co3O4 are effective dopants for improving densification of SnO2 ceramics. According to XRD analysis,Co2SnO4 crystal phase are formed by the reaction between Co3O4 and SnO2,and TiO2 is dissolved into the SnO2 phase. Doping of Sb2O3 can improve the semiconducting processes of SnO2 grains. Co-doping Cr2O3,Ni2O3 and MnO is efficient to improve the nonlinear property and surge current withstanding performance of the materials. The samples with a diameter of 14mm have a nonlinear coefficient (α) of about 50,a breakdown electric filed of about 350V/mm and a leakage current of less than 5μA,and the withstanding surge peak current of 8/20μs waveshape is about 2kA,which meet practical requirement.