SELF-DIFFUSION IN CR2O3 .2. OXYGEN DIFFUSION IN SINGLE-CRYSTALS

Oxygen self-diffusion in chromia (Cr2O3) single crystals was studied as a function of oxygen pressure at 1100-degrees-C, using the gas-solid isotope exchange method. The diffusion experiments were performed in H-2-(H2O)-O-18 atmospheres. After the diffusion anneal, the O-18 diffusion profiles were determined by secondary ion mass spectrometry and the diffusion coefficients were computed using a general solution for the Fick's second law, taking into account evaporation and exchange at the surface. Our results show that oxygen diffusion coefficients at 1100-degrees-C do not depend on the oxygen pressure and are smaller than values given in the literature. Comparison with results concerning chromium self-diffusion in the same Cr2O3 single crystals clearly indicates that oxygen diffusion is faster than chromium diffusion.