Ayub, I.; Berry, F. and Helgason, O.
Iron-57 Mossbauer spectroscopic studies of the high temperature properties of metal-doped iron oxides.
Hyperfine Interactions, 139-140(3-4),
Fe-57 Mossbauer spectra recorded in situ in vacuo from chromium- and gallium-doped Fe3O4 at elevated temperatures show the dopant ions to depress the Curie temperature of Fe3O4 by ca. 70 K. Spectra recorded from aluminium-doped. gamma-Fe2O3 show the onset of conversion to aluminium-doped alpha-Fe2O3 to begin at ca. 750 K, which is ca. 100 K above the conversion temperature for undoped. gamma-Fe2O3. The variation in magnetic hyperfine fields at temperatures exceeding ca. 750 K is similar to that recorded from alpha-Fe2O3 when doped with zinc or magnesium. At temperatures exceeding 900 K the zinc doped alpha-Fe2O3 partially converts to spinel-related ZnFe2O4.
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