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 Ba2‐xSrxCaTeO6 (0≤x≤2) has been studied using X‐ray powder diffraction (XRD) and Raman spectroscopy. According to the Rietveld refinement three phase transitions induced by compositional changes are reported. The transition from the cubic symmetry to tetragonal (Fm m → I4/m) is observed for x between 0.4 and 0.6. The second transition from tetragonal symmetry to monoclinic symmetry with I2/m as a space group takes place between x = 0.6 and 0.8. The third phase transition, monoclinic to monoclinic (I2/m → P21/n), is located between x = 1.4 and 1.6. Furthermore, considerable changes of the compositional dependence of the Raman modes recorded at ambient conditions confirm occurance of the phase transitions revealed by the X‐ray studies.

Keywords

• Ba2‐xSrxCaTeO6 (0≤x≤2)
• X‐ray diffraction
• Raman spectroscopy
• Crystal structure
• Phase transition