A study of the crystal structures and the phase transitions of Sr2FeSbO6, SrCaFeSbO6 and Ca2FeSbO6 double perovskite oxides

Abstract Sr 2 FeSbO 6 , SrCaFeSbO 6 and Ca 2 FeSbO 6 with the double perovskite structure have been synthesized by the conventional solid state reaction process. The crystal structures and phase transitions at low and high temperature were determined from Rietveld refinements of X-ray and neutron powder diffraction data. Sr 2 FeSbO 6 crystallizes at room temperature in a monoclinic system having a space group I 2 / m and not P 2 1 / n space group as was previously reported. The crystal structures of SrCaFeSbO 6 and Ca 2 FeSbO 6 are described with the P 2 1 / n space group. All compounds show partial order of the B-site Fe and Sb cations, with degree of ordering of 89% for Sr 2 FeSbO 6 and 94% for SrCaFeSbO 6 and Ca 2 FeSbO 6 .