Synthesis, crystal Structure and temperature induced phase transition in Ba1/5Sr4/5NiMoO6 double perovskite oxide: : Study by X-ray diffraction and Raman spectroscopy

Abstract

BaCO 3 , SrCO 3 , NiO, MoO 3 precursors were used as starting materials in the synthesis of double perovskite Ba 1/5 Sr 4/5 NiMoO 6 , and their crystal structure at room tempertaure was solved using X-ray powder diffraction. The Rietveld analysis of X–ray powder diffraction patterns show that both compounds adopt a tetragonal structure with space group I4/m, with unit cell parameters a= 5.58537(1) A, c= 7.9066(2) A. The structure can be represented as a three-dimensional network of alternating NiO 6 and MoO 6 octahedra, with Ba and Sr atoms occupying the interstitial spaces. Temperature-induced phase transitions of Ba 1/5 Sr 4/5 NiMoO 6 were investigated by mean of Raman spectroscopy technique at high temperature up to 392 °C. remarkable in the behaviuor of temperature dependence of the modes has been interpreted as a phase transition from the tetragonal (I4/m) to the cubic ( ) structure.