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 alpha-SiAlON nuclei, a combination of stabilizing cations, Y + Yb, was used; to encourage formation of acicular alpha-SiAlON grains, a small amount of an extra liquid (similar to3 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 degreesC). 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.