Effect of starting composition, type of rare earth sintering additive and amount of liquid phase on alpha reversible arrow beta sialon transformation

Abstract

Five different alpha-beta sialon and alpha-sialon compositions have been prepared using different rare earth oxide additives namely, neodymium, samarium, dysprosium and ytterbium., Post-sintering heat treatments have been carried out at 1450 degrees C for up to 720 h (one month) to observe alpha --> beta sialon transformation. A combination of X-ray and microstructural observations has shown that the high-temperature stability of the alpha-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 beta-sialon grains in the initial sintered material