Comparison of the effectiveness of rare-earth sintering additives on the high-temperature stability of α-sialon ceramics

α-sialon starting compositions with m=1 and n=1.7 have been densified by either hot-pressing or pressureless sintering using Y₂O₃ and Ln₂O₃ additions where Ln is neodymium, samarium, dysprosium or ytterbium. The resulting materials have been heat treated at 1450°C to crystallize the grain-boundary liquid into crystalline oxynitride phases. The effect of sintering additive on the design of final properties has been studied and Dy₂O₃ was found to be the best sintering additive to obtain desirable properties for α-sialon and also α-β sialon materials.