Effect of HfO2 Addition on Mechanical Properties of SiAlON-Based ceramics

α/β-SiAlON-based ceramics were fabricated by sintering a mixture of Si 3 N 4 and Ln-α-SiAlON powder prepared from imide-derived amorphous Si 3 N 4 (where Ln=Y, Er and Yb). The effect of HfO 2 addition on the microstructure and thermomechanical properties of Ln-SiAlON-based ceramics was studied. A small amount of HfO 2 addition had a substantial influence on the development of inhomogeneous microstructure including grain growth and broadening of grain size distribution, which resulted in the increase of bending strength and fracture toughness, K IC . Yb-SiAlON-based ceramics doped with a small amount of HfO 2 exhibited excellent hightemperature strength and oxidation resistance which were controlled by the ionic radii of Ln-elements.