The Influence of Excess Precipitate on the Non-Ohmic Properties of SnO2-Based Varistors

Based on our background in the field of nonlinear electrical properties of SnO₂-based varistors, we have been observing the influence of microstructural heterogeneities, e.g., the precipitate phase at triple points of the grain boundary region. In this study, we have prepared a SnO₂-based varistor system with excess precipitates at triple points in the grain boundary region in order to discuss their influence on the system's non-ohmic properties, including thermal treatment at oxidizing atmospheres. Our results indicate that an excessive amount of such precipitates may be deleterious to the non-ohmic properties because they may create adjacent regions at grain boundaries with lower concentrations of segregated metal atoms, thus increasing the presence of a non-active potential barrier and increasing leakage current paths. Under these circumstances, the effect of thermal treatment in oxidizing atmospheres is to decrease the leakage current density instead of increasing the nonlinear coefficient.