The effect of sintering temperature variations on the development of electrically active interfaces in zinc oxide based varistors

A series of zinc oxide based varistors containing 0.5 wt.% Bi2O3 and 0.5 wt.% Mn2O3 were prepared by a conventional mixed oxide route and sintered at temperatures between 950 and 1300°C. All samples showed the varistor effect, although as the sintering temperature was increased above 1000°C, the non-linear coefficient decreased from 22 to 3 at 1300°C. Local grain boundary property measurements were carried out using remote electron beam induced current (REBIC) configuration conductive mode scanning electron microscopy. The proportions of electrically active interfaces and those showing strong resistive contrast were found to increase with sintering temperature.