Nonlinear I-V characteristics of Ta2O5-, Nb2O5-, V2O5-Doped SnO2 based varistor ceramics

The influence of doping on the nonlinear electric properties of Nb2O5, Ta2O5, V2O5 doped SnO2+CoO+ZnO varistor ceramics has been studied by measuring the nonlinear coefficient, the breakdown field, the barrier height and ac conductivity as functions of the temperature, the electric field and the frequency. The un-doped SCZ ceramics showed varistor characteristics, such as a nonlinear coefficient (alpha = 2.94) and breakdown electric field (E-B = 1760 V/cm) at the room temperature. The TA(2)O(5) and V2O5 doped SCZ:Ta and SCZ:V ceramics displayed no varistor characteristics at the room temperature. However, the Nb2O5 doped SCZ:Nb ceramics exhibited enhanced varistor characteristics (alpha = 17.2, E-B = 5064 V/cm) at the room temperature. The advanced varistor characteristics of SCZ:Nb ceramics can be explained by the formation of oxygen species, such as O', O ''.