X-ray diffraction and Raman spectroscopy studies of temperature and composition induced phase transitions in Ba2-xSrxZnWO6 (0 ≤ x ≤ 2) double perovskite oxides

X-ray diffraction and Raman spectroscopy studies of Sr doped double perovskites compound Ba2-xSrxZnWO6 with (0 <= x <= 2) were investigated. As a function of composition while increasing strontium amount, the samples show two phase transitions from cubic to tetragonal phase and from tetragonal to monoclinic structure. Both Rietveld refinements and Raman studies showed that the first phase transition occurs between x = 1 and 1.2; the second phase transition is observed around x = 2. Furthermore, increasing the temperature for the compositions (1.2 <= x <= 2), manifests the tetragonal to cubic phase transition. For x = 2 two phase transitions were observed as a function of temperature. For this series, the phase transitions are illustrated by considerable changes in the composition and temperature dependence of the modes. All the Raman modes show a linear behavior when the composition or temperature is increased, then the slope change indicating the symmetry change. (C) 2012 Elsevier B.V. All rights reserved.