Oxidation of pressureless sintered Si2N2O materials

Abstract The oxidation behaviour of pressureless sintered Si 2 N 2 O materials prepared from both amorphous and crystalline starting powders has been examined. The materials exhibited excellent oxidation resistance at temperatures of up to 1350°C. Thin protective oxide scales formed which had a duplex morphology after long exposures to air at high temperatures. Substantial crystallisation of the intergranular glass phase with formation of Y 2 Si 2 O 7 occurred during oxidation at 1200°C and 1350°C. Catastrophic oxidation occurred at temperatures ≥ 1400°C. This behaviour is enhanced by an oxidation-induced shift in the composition of the material to a liquid-forming region in the Y-Si-Al-O-N system.