Phase relationships and microstructures of Ca and Al-rich α-sialon ceramics

Ca sialon compositions rich in Al and Ca were fabricated and characterised in this work. Sintered compositions are found to be dominated by AlN′ and AlN-polytypoid phases. Large quantities of grain boundary glass are also present. Analysis of crystalline phases provided phase assemblage information for compositions with high m and n values and led to the refinement of an existing phase behaviour diagram. A modified phase behaviour diagram incorporating the current work has been proposed. Microstructural and fracture surface features are examined by a scanning electron microscope (SEM). a Sialon grains in these compositions have been observed with an elongated morphology.