Reversible a to b transformation in a textured Sm-sialon ceramic
A preferential orientation was observed in a Sm-sialon ceramic, of the composition Sm0.4Si9.6Al2.4O1.2N14.8, after hot pressing at 1800 °C for 2 h. Post-sintering heat treatment was performed at 1450 °C for 384 h, resulting in the forward α′ → β′ transformation, accompanied by the formation of M′SS and an increase in the 21R phase. Subsequent heat treatment at 1800 °C for 2 h resulted in the reverse β′ → α′ transformation, with a corresponding decrease in the M′SS and 21R phases. This confirms the fully reversible reaction of α′+liquid ↔ β′+M'ss+21R in Sm-sialon ceramics. In addition, the texture introduced by hot pressing was maintained after all heat treatments, indicating that there is a crystallographic relationship between the transformation phases. The microstructure and mechanical properties were also found to be mostly reversible, contrary to the behaviour of the α′ lattice parameters and bulk density.
Carman, A., Pereloma, E. and Cheng, Y. (2011). Reversible α′ → β′ transformation in a textured Sm-sialon ceramic. Journal of the European Ceramic Society, 31 (6), 1165-1175.