High voltage SnO2 varistors prepared from nanocrystalline powders

In this study, SnO2-based varistors were prepared from mechanically activated nanocrystalline powders. Nanocrystalline powders were derived by subjecting the initial powders to intensive high-energy activation with different times and ball to powder ratio. The effect of activation parameters on the powder properties and sintering temperature, as well as microstructural, micro-electrical and macro-electrical properties of the final specimens was evaluated. Varistors derived from high-energy mechanical activation exhibit a higher density (98.3% relative density) and more refined microstructure upon sintering at 1,300 A degrees C in comparison varistors prepared from conventional powders. Breakdown voltage and nonlinear coefficient were increased up to 24 kV/cm and 45 respectively.