119Sn Mössbauer studies on ferromagnetic and photocatalytic Sn–TiO2 nanocrystals

Diluted Sn doped TiO 2 nanocrystals (Sn/Ti ratio: x ≤ 1.37 %) were synthesized by a simple hydrothermal method using pure reagents without any surfactant and dispersant material. The XRD of these samples showed an anatase phase, anatase and rutile mixed phases, and a rutile phase of TiO 2 and SnO 2 with the increase of Sn dopant concentrations. 119 Sn Mössbauer spectra gave the broad peaks, which were decomposed into doublets and sextets because almost all these samples showed magnetic hysteresis even at room temperature. The titanium oxides doped with x ≤ 0.12 % showed the relatively large magnetic hysteresis and high photocatalytic activity. Mössbauer spectra of samples doped with x > 0.3 % were analyzed by one doublet and two sextets although the samples showed weak ferromagnetism. Three kinds of Sn species may be distinguished as Sn 4+ substituted TiO 2 and two different magnetic arrangements of Sn doped TiO 2 : one with more oxygen defects and other at the interface of TiO 2 and precipitated SnO 2 containing Ti atoms. The correlation between various amounts of Sn sites and photocatalytic activity and/ or magnetic property was discussed.