An investigation of the local environments of tin in tin-doped α-Fe2O3

The extended x-ray absorption fine structure (EXAFS) recorded from tin-doped alpha-Fe2O3, prepared by the mechanical milling of tin dioxide and alpha-Fe2O3 and by the hydrothermal processing of iron- acid tin-containing precipitates, can be interpreted in terms of a model in which tin occupies both substitutional octahedral sites and the interstitial octahedral sites in the corundum-related alpha-Fe2O3 structure. The EXAFS and Sn-119 Mossbauer spectra suggest that structural models derived from x-ray powder diffraction data do not adequately describe the complexity of the local environment of tin in alpha-Fe2O3. In particular, the EXAFS and Sn-119 Mossbauer spectra recorded from materials made by mechanical milling show evidence of more disorder. The Sn-119 Mossbauer spectra also indicate that the degree of order in the materials made by both methods is far from perfect and that the microstructural defects are highly sensitive to tin content and the preparative method.