An investigation of the local environments of tin in tin-dopedα-Fe2O3

Abstract

The extended x-ray absorption fine structure (EXAFS) recorded from tin-dopedα-Fe2O3, prepared by the mechanical milling of tindioxide and α-Fe2O3 and by the hydrothermal processing ofiron- and tin-containing precipitates, can be interpreted in terms of a modelin which tin occupies both substitutional octahedral sites and theinterstitial octahedral sites in the corundum-related α-Fe2O3 structure. The EXAFS and 119Sn Mössbauer spectra suggest thatstructural models derived from x-ray powder diffraction data do not adequatelydescribe the complexity of the local environment of tin in α-Fe2O3. In particular, the EXAFS and 119Sn Mössbauer spectrarecorded from materials made by mechanical milling show evidence of moredisorder. The 119Sn Mössbauer spectra also indicate that the degree oforder in the materials made by both methods is far from perfect and that themicrostructural defects are highly sensitive to tin content and thepreparative method.