Preparation and characterisation of tin-doped alpha-FeOOH (goethite)

Tin-doped alpha-FeOOH (goethite) has been prepared directly by the hydrothe rmal processing of a precipitate. The morphology of the crystals, which is reflected in the Fe-57 Mossbauer spectra, depends on the pH of the precipit ating media. The Sn-119 Mossbauer spectra are consistent with a complex mic rostructure around the octahedrally coordinated tin ions in the goethite st ructure and are sensitive to the changes in the magnetic structure of alpha -FeOOH resulting from tin doping. Fe-57 Mossbauer spectroscopy and electron microscopy show acicular tin-doped alpha-FeOOH to be converted to tin-dope d alpha-Fe2O3 with identical morphology by mild heating in air.