Transmission electron microscopy observation in a liquid-phase-sintered SiC with oxynitride glass

Using a pure alpha -SiC starting powder and an oxynitride glass composition from the Y-Mg-Si-Al-O-N system as a sintering additive, a powder mixture w as hot-pressed at 1850 degreesC for 1 h under a pressure of 20 MPa and furt her annealed at 2000 degreesC for 4 h in a nitrogen atmosphere of 0.1 MPa. High-resolution electron microscopy and x-ray diffraction studies confirmed that a small amount of beta -SiC was observed in the liquid-phase-sintered alpha -SiC with this oxynitride glass, indicating stability of beta -SiC e ven at high annealing temperature, due to the nitrogen-containing liquid ph ase.