Crystal structure, phonon modes and dielectric properties of B site ordered ABiLiTeO6 (A = Ba, Sr) double perovskites

ABiLiTeO6 (A = Ba, Sr) double perovskite oxides were synthesised through conventional solid - state ceramic route. X-Ray diffraction patterns indicated pseudocubic symmetry for both compounds. Deconvoluted Raman spectra using Lorentzian function gave 7 first order Raman modes for both BaBiLiTeO6 and SrBiLiTeO6 whereas Infrared spectroscopy gave 8 modes for BaBiLiTeO6 and 9 modes for SrBiLiTeO6. Observed phonon modes were in good agreement with the corresponding group theoretical predictions for space group I4/m for both compounds. Rietveld refinement of the XRD patterns also confirmed I4/m space group for ABiLiTeO6 (A = Ba, Sr) with 1:1 B site ordering of Te6+ and Li+ cations. The random occupancy of Ba2+ and Bi3+ at the A site in BaBiLiTeO6 whereas Sr2+ and Bi3+ in SrBiLiTeO6 were revealed from Rietveld refinement. Microstructure of both the compounds gave average grain size of less than 3 µm. At 1 MHz, BaBiLiTeO6 and SrBiLiTeO6 possess porosity corrected dielectric constants of 49.5 and 34.4 and dielectric losses of 0.029 and 0.028 respectively.