Abstract
β-Sialon (Si6−zAlzOzN8−z) withz = 0.5 was fabricated by hot-pressing of a spray dried mixture of α−Si3N4 and aluminium-isopropoxide solution. Phase composition, flexural strength and microstructure of a sintered body were investigated. Phases identified by XRD were β-Sialon and a small amount of O′-Sialon. The flexural strength (three-point bending) was about 1500 MN m−2. This value, about three times higher than that of β-Sialon fabricated from α-Si3N4 and α-Al2O3 powder, was mainly due to the homogeneous microstructure without large defects such like clusters of large grains. β-Sialon was heat treated at 2000 °C for 2 h in 4 M Pa N2 to develop elongated β-Sialon grains with high aspect ratio. Microstructure, flexural strength and fracture toughness (KIc) of it were investigated. Both strength andKIc were lower than those of hot-pressed sample, even though an elongated microstructure was achieved. This fact showed that the toughening of β-Sialon with elongated grains could not be achieved without grain boundary phase which resulted in a crack deflection.
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