Nonlinear electrical properties of cobalt doped SnO2 center dot Ni2O3 center dot Nb2O5 varistors

A new varistor system of SnO2. Ni2O3. Nb2O5 exhibits the relative dissatisf actory physical and electrical properties. The effect of cobalt oxide on th e properties of the SnO2. Ni2O3. Nb2O5 varistors was investigated by measur ing the densities, permittivities, the current-voltage properties and the p roperties of the defect barriers. It is found that the sample doped with 0. 25 mol% Co2O3 exhibits the abnormal poorer electrical properties than the s amples without Co2O3 dopants. However, the sample doped with 6.0 mol% Co2O3 exhibits the highest nonlinear coefficient (alpha = 17.24) and reference e lectrical field (E-B = 561 V/mm), although the sample doped with 1.0 mol% C o2O3 exhibits the highest densities (rho = 6.87 g/cm(3)) and permittivities . The sample with 6.0 mol% Co2O3 bears the highest barriers, but the sample with 1.0 mol% Co2O3 shows the narrowest barriers. The investigation of the sintering temperature shows that the samples sintered at 1450 degreesC exh ibit the better physical and electrical properties. The results were discus sed and the defect barrier model was also introduced to explain.