Phase Transformations in Sm (α+β)-SiAlON Ceramics during Post-sintering Heat Treatments

摘要

Phase transformations in Sm (α + β)-SiAlON ceramics during post-sintering heat treatments at 1300 and 1450℃ were investigated using XRD, SEM, TEM and EDS techniques. The transformation from a to p SiAlON, (i.e. α' to β') phases was observed at both temperatures. However, other phase transformations occur simultaneously at grain boundaries of the materials and also involve the β' phase, namely, Glass → SmAlO_3 + β' and SmAlO_3 + β' → M'. Their effects on the amount of β' in the materials must therefore be considered in the study of the α' to β' transformation. It is thought that the increase in the β':(α' + β') ratio during a heat treatment process depends not only on the rate of the α' to β' transformation, but also on the amount and composition of the intergranular phases.