Effect of oxygen vacancies in Ta2O5-doped SnO2 ceramics on thermal conductivity and varistor characteristics

The effects of Ta doping on the thermal and electrical properties of SnO2 varistors were researched. The results showed that the thermal conductivity is 2.01 WK(-1)m(-1), the nonlinearity coefficient is 43, and the leakage current density is 0.7 mu A/cm2 when the Ta doping level reaches 0.2 mol%. According to the measurement results of the EPR, SEM/EDS, and XRD, the Ta dopant can reduce the oxygen vacancy concentration, which was generated during the sintering. The decline of the oxygen vacancy concentration reduces the phonon scattering, then the thermal conductivity of the varistors is improved. On the other hand, the reduction of the oxygen vacancy concentration elevates the barrier height, so the nonlinearity coefficient is improved and the leakage current density is declined.