Grain Growth in (Ga, Mn)-Codoped ZnO Ceramics
Grain growth in Ga2O3 and MnO co-doped ZnO was investigated for sintering from 950° to 1250°C in air. Microstructural observation revealed that the samples sintered at lower temperatures consist of uniform equiaxed grains while the samples sintered at higher temperatures consist of plat-like grains, implying that the grain growth mechanism for the examined ZnO ceramics changes when the sintering temperature increases above about 1150°C. The traditional kinetic grain growth equation was employed to analyze the variation of grain size with sintering temperature and sintering holding time. It was shown that the grain growth exponent, n, increases from 2.17 for samples with uniform equiaxed grain structure to 4.30 for samples with plate like grain structure, while the apparent activation energy, Q, increases from 237 kJ/mol for low-temperature-sintered sample to 405 kJ/mol for high-temperature-sintered samples. The increases in both n and Q were mainly attributed to the difference between the grain morphologies in low- and high-temperature ranges. The underestimation of the sizes of the plate-like grains was also considered to be another important origin for the higher values of n and Q for the high-temperature-sintered samples.
Yiwang Bao, Danyu Jiang, Li Tian and Jianghong Gong
B. Shen et al., "Grain Growth in (Ga, Mn)-Codoped ZnO Ceramics", Key Engineering Materials, Vol. 492, pp. 250-255, 2012