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.