Liquid-phase sintered silicon carbide with aluminum nitride and rare-earth oxide additives

SiC was sintered with AlN and Y₂O₃ as sintering additives by spark plasma sintering (SPS). Using nano-sized β-SiC powder as the starting material, the sintered density reached about 95% of theoretical at 1800-2000°C for 10min. The β to a phase transformation of SiC was not found by XRD. The secondary phase such as Y₂O₃ decreased as the firing temperature was elevated, and β-SiC monophase was identified at 2000°C. It seems that the residual intergranular glassy phase is present between the SiC grains. Significant SiC grain growth was observed at 1800-1900°C by SEM. The grain size decreased with increasing amount of AlN additive. The maximum value of flexural strength of the sample reached approximately 800MPa. These results are discussed on the basis of the liquid-phase sintering mechanism in AlN-Y₂O₃ and AlOs ₂Os systems.