Effect of step sintering on breakdown voltage of varistors prepared from nanomaterials by sol gel route

摘要

ZnO varistor materials were prepared by a sol gel route with subsequent drying and calcination.Varistor discs fabricated from these materials were subjected to a two step sintering schedule.Therefore in a typical experiment, the samples were heated to 1000uC, then allowed to cool for over30 min to 900uC and held there for 6 h. The results were compared with commercial varistor samplessintered in a similar way. Considerably higher breakdown voltages were obtained for the varistorsmadefrom nanosample (1192¡30 V mm21) compared with the commercial samples (723 ¡30 V mm21)sintered under the same experimental conditions. The sintered materials were characterised by X-raydiffraction (XRD), field emission scanning electron microscopy (FESEM) and density measurements.