Crystallization from Na2O-P2O5-Fe2O3-MIIO (MII = Mg, Ni) melts and the structure of Na4MgFe(PO4)3

We have studied general trends of phosphate crystallization from Na2O-P2O5-Fe2O3-(MO)-O-II (M-II = Mg, Ni) high-temperature solutions at Na/P = 1.0-1.4, M-II/Fe = 1.0, and Fe/P = 0.15 or 0.3, and identified the stability regions of the phosphates (Na4MFe)-Fe-II(PO4)(3) (M-II = Mg, Ni), NaFeP2O7, and Na2NiP2O7. The synthesized compounds have been characterized by X-ray powder diffraction and infrared spectroscopy. The structure of Na4MgFe(PO4)(3) (sp. gr. R (3) over barc, a = 8.83954(13) , c = 21.4683(4) ) has been determined by Rietveld powder diffraction analysis.