Nonlinear electrical properties of SnO2·Li2O·Ta2O5 varistors

The electrical properties of (Ta, Li)-doped SnO2 ceramics as a new varistor material were investigated. The sample 98.90% SnO2·1.0% Li2O·0.10% Ta2O5 (mol fraction) sintered at 1500 °C possesses the highest density (ρ=6.63 g/cm3) and nonlinear electrical coefficient (α=10.8). Effect of dopants and sintering temperature on the properties of the samples were investigated. The substitution of Sn4+ with Li+ and the variation of sintering temperature play very important effects on the densities, dielectric constant, nonlinear electrical properties and other characteristics of the samples. The samples sintered at 1500 °C exhibit better physical and electrical properties than the samples sintered at 1400 °C. The properties of the grain-boundary defect barriers and the microstructural characteristics were investigated to ensure the effect of the dopants and the sintering temperature. A grain-boundary defect barrier model was used to illustrate the grain boundary barrier formation in SnO2·Li2O·Ta2O5 varistors. PACS numbers: 74.40.Lq; 72.20.Ht