Berry, Frank; Helgason, Om; Moore, Elaine; Mosselmans, Frederick and Ren, Xiaolin
The Magnetic hyperfine field in tin-doped Fe3O4: variations during oxidation and subsequent phase transformations.
Journal of Physics: Condensed Matter, 16(28),
Tin K-edge EXAFS recorded in situ at 498 K from tin-doped Fe3O4 show that the octahedral coordination of tin in the inverse spinel-related structure remains essentially unchanged as it is oxidized to structurally-related γ-Fe2O3. Changes in the magnetic hyperfine field distributions in the tin-119 Mossbauer spectra recorded in situ between 285 and 500 K show that at the higher temperatures some of the tin-doped Fe3O4 is converted to structurally-related tin-doped γ-Fe2O3. Comparison with data recorded from similar materials by 57Fe Mossbauer spectroscopy show that the phase transition is sensitive to the partial pressure of oxygen and the period of time at the elevated temperatures. The changes in the magnetic hyperfine field distributions show that conversion of tin-doped Fe3O4 to tin-doped γ-Fe2O3 is largely completed at 600K and occurs without the segregation of tin. At 700 K some tin segregates to form tin dioxide as the conversion of tin-doped Fe3O4 to tin-doped γ-Fe2O3 is completed. At
higher temperatures the inverse spinel-related γ-Fe2O3 phase is converted to the corundum-related α-Fe2O3 structure.
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