PREPARATION AND GRAIN-BOUNDARY DEVITRIFICATION OF SAMARIUM ALPHA-SIALON CERAMICS

The reaction sequence and densification behaviour of Sm alpha-sialon c eramics have been studied. Sm2O3 is an effective sintering aid and den se Sm alpha-sialon ceramics can be prepared by pressureless sintering at 1800-degrees-C for 4 h. Post-sintering heat-treatment produces two different grain boundary phases depending on the heat-treatment temper ature. Below 1400-degrees-C SmAlO3 is stable, and between 1400 and 160 0-degrees-C an Al-containing melilite solid solution (M(SS)') appears at the grain boundaries. Microstructures of the materials before and a fter heat-treatment have been studied and the results are discussed.