The point-defect structure of the doped oxide, (Mg1-xFex)O, was determined quantitatively by means of in situ high-temperature X-ray absorption spectroscopy at 1270 to 1470K. The spectra were recorded at the dopant K-edge, for a given O activity. The degree of oxidation, as a function of temperature and x-value, could be consistently explained by a simple defect model. The latter assumed that divalent Fe ions were randomly dissolved in the cation sub-lattice, and that a defect associate existed which involved 2 trivalent Fe ions and a cation vacancy. There were indications that trivalent ions which occupied interstitial sub-lattice sites were to be found near to the (Mg,Fe)O/Fe2MgO4 phase boundary.

A Quantitative in situ FeK-XAFS Study (T > 1270K) of the Oxidation Degree of Iron in (Mg,Fe)O. N.Hilbrandt, M.Martin: Journal of Synchrotron Radiation, 1999, 6[3], 489-91