Synthesis, structural characterizations and vibrational spectroscopy studies of Ba2 -xPbxSr(PO4)2; (0 ≤ x ≤ 2)

This work aims at synthesizing by reaction in the solid state orthophosphate type compounds usable in different applications (electrochemical performances, laser materials, magnetic materials, ionic conductors, potential in optics, catalysts, sensors, ceramics, etc.). The optimal operating conditions have been determined. The characterization of the materials obtained was carried out from a structural point of view by X-ray diffraction, Raman, and infrared spectroscopies, and morphologically, by scanning electron microscopy coupled with analysis by energy dispersive X-ray spectroscopy and transmission electron microscopy. The Rietveld procedure was used for the refinement investigation, and the findings reveal that the observed and calculated patterns are in excellent agreement. In the complete composition range (0 <= x <= 2), the Ba-2 -xPbxSr(PO4)(2) compounds crystallize in the hexagonal system at space group R (3) over bar m with multiple units per crystal lattice Z = 3 and produce a solid solution. In solid solutions, the a and c lattice parameters varied, with a reduction in the a and c parameters proportional to the radius of the corresponding replaced ions. The M(1) and M(2) positions in the lacunar anionic orthophosphate structure were shown to be preferentially occupied by Pb2+/Ba2+/Sr2+ ions in solid solutions. The vibrational spectra of this solid solution series of crystalline orthophosphate are assigned by comparison with other orthophosphate materials and interpreted based on factor group analysis in space group R (3) over bar m (D-3d(5)). Raman and IR spectroscopy studies give results justifying the crystal symmetry already demonstrated by X-ray diffraction.