The effect of sintering temperature on the development of grain boundary traps in zinc oxide based varistors

A series of zinc oxide based varistors containing 0.5 wt% Bi2O3 and 0.5 wt% Mn2O3 was prepared by a conventional mixed oxide route and sintered at temperatures between 950◦ and 1300◦C. All samples showed varistor behaviour, although as the sintering temperature was increased from 950◦C to 1300◦C, the non-linearity coefficient, α, decreased from 22 to 3. Deep level transient spectroscopy of the varistors showed that the main active electron trap migrated to shallower levels within the bandgap as the sintering temperature increased. At the lowest sintering temperature, where α attained the highest values, a second, shallower trap was also activated. C 2006 Springer Science + Business Media, Inc.