The self-diffusion of 59Fe parallel to the c-axis in single crystals of the oxide was measured at 1150 to 1340C, under O partial pressures of between 2 x 10−3 and 1atm. The temperature dependence of the cation diffusivity in air (table 99) was given by:

D (cm2/s) = 1.9 x 109 exp[-141.4(kcal/mol)/RT]

The unusually large value of D0 was explained in terms of the values of the pre-exponential terms in the reaction constants for the creation of defects in Fe2O3. The O partial-pressure dependence of the diffusivity indicated that cation self-diffusion occurred via an interstitial-type mechanism. The simultaneous diffusion of 52Fe and 59Fe was measured, and the small value of the isotope effect suggested that Fe ions diffused via a non co-linear interstitialcy mechanism. This was consistent with the crystal structure of Fe2O3.

Cation Self-Diffusion and the Isotope Effect in Fe2O3. K.Hoshino, N.L.Peterson: Journal of Physics and Chemistry of Solids, 1985, 46[3], 375-82