Effect of sintering temperature on microstructure and electrical properties of nano Zinc Oxide varistor

Nanometer-sized ZnO powder was synthesized at low decomposing temperature by polyacrylamide-gel method where Acrylamide was used as monomer, and N,N-methylenebisacrylamide as lattice reagent. The characteristic of powders were studied by X-ray diffraction and scanning electron microscope (SEM). The results indicated uniform distribution of nano ZnO particles. Also electrical properties were investigated at different sintering temperatures of 800, 900 and 1000 degrees C. It was observed that increase in sintering temperature, resulted in increase in the grain size of the varistor ceramics. The observed nonlinearity in current - voltage characteristic was explained by the existence of potential barrier at the grain boundaries and lowering of the barriers.