Effect of heating rate on microwave sintering of nanocrystalline zinc oxide

In this study, the effect of heating rates on microwave sintered ZnO was investigated at heating rates ranging from 50 to 100 °C/min. The relative density and heating rate of microwave sintered samples were found to be independent, and faster heating rates were found to result in smaller ZnO grain sizes. The activation energy of grain growth was calculated and showed a tendency to decrease with increasing heating rates. The main microwave sintering mechanism that prevails during ZnO sintering is grain boundary diffusion, and the nonthermal effect is believed to occur particularly at the beginning of sintering.