Si2N2O/Si3N4 composite ceramics were prepared by pressureless sintered a Si3N4 and SiO2 mixture with 2 mol% Sm2O3. The oxidation behavior and high-temperature strength of Si2N2O/Si3N4 composite materials have been examined. The typical oxidation isotherm of Si2N2O/Si3N4 ceramic is represented by an asymptotic law. The oxidation rate for Si2N2O/Si3N4 was low as compared with those for Si3N4 ceramic. Thin protective oxide scales formed after long exposures to air at 1400 oC and substantial crystallization of the intergranular glass phase with formation of Sm10(SiO4)6N2 occurred during oxidation. Besides, Si2N2O/Si3N4 composites showed excellent high-temperature strength like Si3N4 ceramic and the residual strength ratio can be up to 80 % at 1100 oC which is much higher than Si2N2O single-phase ceramic. The degradation of strength at higher temperature results from the increase of interganular glass phase due to diffusion of molecular oxygen.

Keywords: Si2N2O/Si3N4 composite ceramics, Oxidation resistance, High-temperature strength.