The effect of cation type, intergranular phase amount and cation mole ratios on z value and intergranular phase crystallization of SiAlON ceramics

The chemical resistance of SiAlONs is controlled by various factors such as z value, microstructure, type and amount of sintering additives, and intergranular phase nature (amorphous or crystalline). In this study, the relationship between z value and intergranular phase crystallization of αı:βı-SiAlON composites reinforced with TiN (17 wt%) was investigated by using various dopant systems (Y:Sm:Ca, Yb:Sm:Ca, and Er:Sm:Ca) and various amounts of intergranular phase. The effect of TiN on densification, phase assemblage and microstructural evolution of composites was systematically investigated. Further, the effects of variations in the sintering aid amount and cation mole ratios on density, hardness and fracture toughness were determined in relation to z values. It was found that high z value (>0.5), crystalline intergranular phase and appropriate mechanical properties can be achieved by selecting the type of sintering additive, its amount and ratio.