Abstract
In this study, self-reinforced Y-α-SiAlON was prepared by two-step phase transformation using single or dual rare-earth oxide addition. The process was implemented by a two-step sintering technique. The mechanism of two-step phase transformation and microstructure evolution of Y-α-SiAlON with or without Ce2O3 addition were investigated in detail. The predominant phase of the sample after the first step (i.e., pressureless sintering at low temperature) comprised elongated β-SiAlON grains. By contrast, the majority phase of sample after the second step (i.e., gas pressure sintering at high temperature) included coarse, elongated α-SiAlON grains. The driving force for β-to-α SiAlON phase transformation and liquid viscosity decreased, whereas the amount of liquid phase increased because of Ce2O3 addition, which contributed to anisotropic growth and resulted in more elongated α-SiAlON grains. The sample co-doped with Y and Ce exhibited the best mechanical properties with fracture toughness of 7.8 MPa m1/2 and Vickers hardness of 19.81 GPa.
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