Imfluence of α-Alumina Seeds on Transformation of Aluminium Hydroxide and Morphology of Alumina Grain in Hot-Pressing

Abrasives as seeds were introduced to the starting materials of aluminium hydroxide by wet-grinding of high-purity alumina milling balls. The phase transformation from aluminium hydroxide to α-Al2O3 was completed at 1100℃ for 2h by seeds added. The size of alumina particle derived from calcined aluminium hydroxide was reduced and narrow particle size distribution was obtained with increasing amount of the seeds. Alumina grain shapes changed with the amount of introduced seeds: equiaxed grains were observed for the samples without seeds introduction, hexagonal platelets were developed after seeds addition. Finally the grain shape showed a trend to elongated grains with seed concentration up to 20wt%.