Abstract

Tin-doped α-FeOOH (goethite) has been prepared directly by the hydrothermal processing of a precipitate. The morphology of the crystals, which is reflected in the ⁵⁷Fe Mössbauer spectra, depends on the pH of the precipitating media. The ¹¹⁹Sn Mössbauer spectra are consistent with a complex microstructure around the octahedrally coordinated tin ions in the goethite structure and are sensitive to the changes in the magnetic structure of α-FeOOH resulting from tin doping. ⁵⁷Fe Mössbauer spectroscopy and electron microscopy show acicular tin-doped α-FeOOH to be converted to tin-doped α-Fe₂O₃ with identical morphology by mild heating in air.