Morphology and Sinterability of Thermally Treated Carbothermally Synthesized Silicon Nitride Powders

Carbothermally produced alpha-Si₃N₄ powder is thermally treated (1400°-1500°C for 4-12 h) in nitrogen-gas to determine the impact of thermal treatment on powder composition, particle size, morphology, and sinterability. Thermal treatment reduces residual carbon and oxygen content and reduces internal porosity (lower surface area), which results in a rounding of the particles. The lower oxygen content of the heat-treated, carbothermally produced alpha-Si₃N₄ powder allows Y₂O₃-Al₂O₃-SiO₂ sintering formulation to be adjusted so that an improvement in the early stage of densification can be achieved.