FT-Raman and FT-IR vibrational spectroscopic studies of Sr2RESbO6 (RE=La to Lu and Y) double perovskites

► 14 double perovskites Sr2RESbO6 were synthesized. ► Crystal lattice parameters have been obtained. ► IR and Raman spectra have been obtained. ► The crystal structure has been studied. The Sr2RESbO6 double perovskites (RE=La to Lu and Y) were synthesized by ceramic method. The structure and phase purity of the prepared double perovskites were examined by X-ray diffraction pattern and vibrational spectroscopy. A systematic analysis of the compounds structure was carried out for the first time by Raman and IR spectroscopies. A simple inspection of the diffraction patterns shows that these compounds have lower symmetry than the cubic which can be usually found in the Ba2RESbO6 double perovskites. The four active modes (A1g, Eg, and two T2g) in the Raman spectra and the active mode (T1u) in the IR spectra previously described in the spectroscopic data of Ba compounds have changed. In the Sr compounds these modes have been split into its components, in some cases, being active in both types of spectra. According to our data the Sr2RESbO6 double perovskites can be described by a monoclinic symmetry cell, space group P21/n. However, in the cases of Sr2LaSbO6 and Sr2PrSbO6 an alternative structure should be searched by neutron diffraction technique.