Synthesis of .ALPHA.-SiAlON from Different Particle Size of .BETA.-Si3N4.

Abstract

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