Self-Reinforced α-SiAlON Ceramics with Improved Damage Tolerance Developed by a New Processing Strategy

Alpha-SiAlON ceramics with a refined self-reinforced microstructure, i.e., containing acicular grains with dimensions much smaller than those obtained in previous studies, embedded in a matrix consisting of submicrometer-sized isotropic grains, were prepared by applying a rapid one-step sintering procedure. To suppress the overabundant formation of α-SiAlON nuclei, a combination of stabilizing cations, Y + Yb, was used; to encourage formation of acicular α-SiAlON grains, a small amount of an extra liquid (∼3 vol%) was introduced; to avoid abnormal grain coarsening resulting from dynamic ripening, the final sintering temperature was set to just slightly above the minimum temperature threshold for activating grain growth (1700°C). The fully dense compacts obtained exhibited excellent thermal-shock resistance, and hardness and fracture toughness values of 20 GPa and 5.1 MPa·m^1/2, respectively.