Crystal structure and phase transitions in new series of double perovskite oxides Ba2-xSrxCaTeO6 (0≤x≤2): X-ray diffraction and Raman spectroscopy studies

Abstract

The structure stability of double perovskite ceramics Ba 2-x Sr x CaTeO 6 (0≤x≤2) has been studied using X-ray powder diffraction (XRD) and Raman spectroscopy. According to the Rietveld refinement three phases transition induced by composition were reported. The transition from the cubic symmetry to tetragonal ( F m m → I 4/ m ) is observed between x= 0.4 and 0.6. The second transition from tetragonal symmetry to monoclinic symmetry with I2/m as space group takes place between x = 0.6 and 0.8. The third phase transition monoclinic to monoclinic ( I 2/ m → P 2 1 / n ) is located between x = 1.4 and 1.6. Furthermore, considerable changes of the composition dependence of the Raman modes recorded at ambient conditions confirm the phase transitions reported by X-ray studies.