EFFECT OF DIFFERENT NUCLEATION TEMPERATURES ON THE GRAIN MORPHOLOGY OF ALPHA-SiAlON CERAMICS

Nitrogen-rich yttrium-cerium-containing multi-cation alpha-SiAlON starting compositions were prepared by gas pressure sintering using conventional alpha-Si3N4 powder. Microstructural characterisation of the two stage sintered materials showed elongated alpha-SiAlON grains in various conditions. The effect of different nucleation temperatures (1400, 1500 and 1600 C) and times (5 and 20 min) on the grain morphology of the alpha-SiAlON ceramics was examined. It was found that needle-like grains were formed in all circumstances. In order to control the properties by tailoring the microstructure, a fundamental understanding of the nucleation and growth of the elongated grains is necessary. 9 refs.