Mössbauer effect study of the Fe-substituted NASICON

Fe-substituted NASICON was prepared by co-precipitation method and the content of iron at different oxidation states was estimated by Mössbauer spectroscopy (MS). Compounds with different phase composition were obtained depending on the preparation procedure. In the case of samples sintered in reducing atmosphere, NASICON containing di- and trivalent iron was detected. The lattice constants were calculated by Rietveld method. Higher values of the unit cell parameters for Na3Zr1−yFe1−y2+Fe2y3+P3O12 compared to the structural analogue γ-Na3Fe2P3O12 indicated the partial replacement of smaller Fe3+ ions by bigger Fe2+ and Zr4+ in the NASICON lattice. The validation of Mössbauer spectroscopy as the useful tool in the calculation of iron content was also performed. The sintering in air led to the multiphase product, which was identified by XRD and MS.