Dense SiC ceramics prepared by using amorphous sintering additives

Spark plasma sintered SiC-based ceramics with amorphous Y₂O₃–Al₂O₃–SiO₂ and CaO–Al₂O₃ sintering additives prepared by melt-quench approach, were compared with those with the direct addition of raw Y₂O₃–Al₂O₃–SiO₂ and CaO–Al₂O₃ mixture. The relative densities of SiC-based with raw Y₂O₃–Al₂O₃–SiO₂ and CaO–Al₂O₃ were 95.3% and 94.3%, respectively. In spite of the same composition of sintering additive, the relative densities of SiC-based ceramics reached the values of 98.9% and 99.5% by using the glassy additives of Y₂O₃–Al₂O₃–SiO₂ and CaO–Al₂O₃, respectively, and the hardness of SiC-based ceramics was improved by about 22.2% and 17.2%, respectively. The amorphous sintering additive effectively improved the densification and hardness of SiC ceramics.