Abstract
Silicon oxynitride (Si2N2O) ceramics were fabricated from equi-molar mixtures of Si3N4 and SiO2 with 5 wt % Al2O3 as a sintering aid by heating at 1650-1950°C for 1 h in 980 KPa N2. The initial stage of densification was due to the solution and repreci-pitation of Si3N4 through a liquid phase of SiO2-Al2O3 system. At>1750°C, further densification took place accompanied by Si2N2O formation and anisotropic grain growth. The thermal decomposition of Si2N2O at the surface of compact lowered the density at>1850°C. The stability of solid phases under sintering conditions was discussed in relation to calculated SiO partial pressures on solids.
