Thermal stability of rare earth densified α-sialon ceramics

Typical α-sialon and mixed α-β sialon starting compositions were densified by either hot pressing or pressureless sintering using the oxides of Yb, Dy, Sm and Nd. The resulting materials were heat-treated at 1450°C for up to 720 hours (1 month) to observe α → β sialon transformation. The results of microstructural characteristics and the phase assembly showed that the high temperature stability of α-sialon phase depends on the starting composition, the type of rare earth sintering additives, the amount and viscosity of the liquid phase, and the presence or absence of ß-sialon grains in the initial sintered material.