High-temperature compressive deformation of β-SiAlON polycrystals containing minimum amount of intergranular glass phase

Abstract

The deformation of equiaxed dense β-SiAlON polycrystals with an average grain size of 0.83 μm was investigated by compression tests at temperatures ranging from 1823 K to 1973 K. The β-SiAlON ceramics were fabricated from β-SiAlON nano-powder (Si 3Al 3O 3N 5) using the Spark-Plasma Sintering technique without additives. The sintered body contained almost no intergranular phase. The deformation was characterized by stress exponent n ∼ 1 in the higher stress region and n ∼ 2 in the lower stress region. The observed values of stress exponent and activation energy, Q ∼ 940 kJ/mol, in the higher stress region were close to those of a SiAlON, which was fully crystallized by annealing for a long time. The possible deformation mechanism of β-SiAlON was attributed to diffusion-related mechanisms, such as grain boundary sliding accommodated by diffusional creep.