Iron Diffusion in Iron‐Aluminate Spinels

Abstract

The diffusion coefficient of 59 Fe in iron‐aluminate spinels (Fe 3 O 4 ‐FeAl 2 O 4 ) was measured by serial sectioning. The results were analyzed with a defect model, assuming that the predominant defects were cation vacancies and interstitials. At 1380°C, diffusion occurs in Fe 3 O 4 and Fe(Fe 1.51 Al 0.49) )O 4 by an interstitial mechanism at low P O2 and a vacancy mechanism at high P O2 * Diffusion of iron is by the vacancy mechanism for higher hercynite concentrations, except that the results for the end‐member, FeAl 2 O 4 , suggest an interstitial mechanism. At 10 −6 atm O 2 , an Arrhenius plot of D Fe exhibits a minimum for Fe 3 O 4 and Fe(Fe 1.51 A1 0.49 )O 4 . This effect is explained in terms of a mechanism change. The D Fe is essentially independent of temperature in Fe(Fe 1.03 Al 0.97 )O 4 and Fe(Fe 0.54 Al 1.46 )O 4 .