Abstract: Grain growth and electrical properties in ZnO system with various valence states of manganese and cobalt were studied. The results were discussed by means of defects
produced by the additions. The grain growth was analyzed from the kinetic grian growth equation: Gⁿ=Dtexp(-E/RT). The results show that the grain growth kinetic exponent
n is 6 and activation energy is 224±17kJ/mol. The grain size increases with the valence states of manganese and cobalt. Raising the firing temperatures can decrease
the breakdown voltage, but the leakage current will increase and its nonlinear coefficient will decline when the firing temperature is too high. In general, the firing temperature is not
exceed 1250℃.

Key words: grain growth, electrical property, valence state