Synthesis of alpha-SiAlON from different particle size of beta-Si3N4

beta-Si3N4 powders with different particle size, AlN and Y2O3 were used as starting materials to fabricate alpha-SiAlON by hot-pressing. Five mass% of commercial alpha-SiAlON powder was also added as seeds to these mixtures t o increase the formation rate of alpha-SiAlON. No significant increase in t he alpha-SiAlON content was found by seed addition when coarse beta-Si3N4 p owder was used. However, in samples sintered from fine beta-Si3N4 powder, t he addition of seeds promoted alpha-SiAlON formation and a content of 100 m ass % (compared to the 60 mass % without seed) could be achieved. When the starting powder beta-Si3N4 was coarse, large alpha-SiAlON and beta-Si3N4 gr ains were obtained, the residual beta-Si3N4 phase being located within the alpha-SiAlON grains also could be found. In principle fine-grained beta-Si3 N4 and alpha-SiAlON could both form from fine beta-Si3N4 powder, residual b eta-Si3N4 was hardly deserved within alpha-SiAlON grains.