Structural studies of nanocrystalline SnO2 doped with antimony:: XRD and Mossbauer spectroscopy

A series of Sb-doped SnO2 samples, with doping levels 0, 3.1, 6.2, 11.9 and 14.0 at% Sb, has been hydrothermally prepared and characterized by X-ray powder diffraction. Diffraction lines were broadened, the line broadening being anisotropic. Both the line broadening and line anisotropy were dependent on the Sb doping level. The samples are tetragonal, space group P4(2)/mnm and isostructural with TiO2(rutile). Sb doping of SnO2 causes the increase of unit-cell parameters. The structure of pure SnO2 and of samples containing 6.2 and 11.9 at% Sb has been refined by the Rietveld method. Crystal structure indicated that both Sb3+ and Sb5+ are substituted for Sn4+ in the SnO2 structure, Sb3+ being dominant for the investigated doped samples. The samples were also examined by Sn-119- and Sb-121-Mossbauer spectroscopy. Mossbauer spectroscopy confirmed the XRD results. Also, the values of the isomer shifts and quadrupole coupling constants indicated that the configuration around the Sb3+ Site includes the presence of the stereochemically active lone pair electrons. (C) 2002 Elsevier Science Ltd. All rights reserved.