SELF-DIFFUSION IN CR2O3 .1. CHROMIUM DIFFUSION IN SINGLE-CRYSTALS

Chromium self-diffusion coefficients in chromia (Cr2O3) single crystals were determined by both ion implantation and thick-film methods, using the Cr-54 and Cr-50 isotopes. The concentration profiles were established by secondary-ion mass spectrometry, and the diffusion coefficients were computed using a solution of Fick's law taking into account evaporation and exchange at the surface. Chromium diffusion was studied as a function of temperature T and oxygen pressure p(O2). Both methods lead to diffusion coefficients of the same order of magnitude. The diffusion coefficients are lower than those given in the literature and do not depend on the oxygen pressure; they are well described by the relation D(Cr) (cm2 s-1) = 5.84 x 10(-9) p(O2)0 exp (-280 kJ mol-1/RT).