Oxidation behavior of liquid-phase sintered SiC with AlN and Er2O3 additives between 1200 °C and 1400 °C

The oxidation behavior of liquid-phase sintered SiC, with AlN and Er2O3 additives, was investigated in air between 1200 °C and 1400 °C, for up to 200 h. The material showed high oxidation resistance at and below 1300 °C, however, the oxidation resistance degraded significantly at 1400 °C. The parabolic weight gain versus oxidation time was measured only for the period of 30–200 h. The apparent oxidation activation energy, Q, was determined to be ≈600 kJ/mol. The major oxidation products consisted of SiO2 (α-cristobalite) and Er2Si2O7. These oxidation products crystallized from the surface amorphous silicate phase during oxidation. The morphology of the microstructure of the oxidized surfaces was shown to be dependent on oxidation temperature. The most probably rate-limiting step was the migration of additive cations along the residual intergranular amorphous phase to the interface between the oxide layer and the SiC bulk.