A fabrication process has been developed for incorporating X-phase into mullite by the reaction of β-Sialon and mullite under firing. The composites were made by pressureless sintering at 1600-1750°C in vacuum atmosphere, covered with packing powder of mullite. The firing temperature was optimized to be 1700°C because the decomposition of X-phase occurs above 1720°C.
The amount of X-phase increased with the addition of β-Sialon(Z=2) powder, and there was no β-Sialon in the composite. It was guessed that the liquid phase in the mullite reacted with β-Sialon to produce X-phase. It was found that the composites (3-10% β-Sialon addition) were almost densified after firing for 2 hours at 1700°C.
