Crystal structure, Mössbauer spectroscopy, and magnetic properties of a new potassium iron oxyphosphate K11Fe15(PO4)18O related to the Langbeinite-like compounds

new potassium iron phosphate K11Fe15(PO4)18O has been synthesized by the flux method and characterized by single-crystal X-ray diffraction. The compound crystallizes in the cubic system with the space group P213 and the cell parameter a=9.917(2) Å. The unit cell contains one formula unit K7.33Fe10(PO4)12O0.66. The structure is closely related to that of the Langbeinite-like compounds, the main difference being the existence of a four-coordinated iron atom in the structure of the oxyphosphate. K11Fe15(PO4)18O adopts a complex three-dimensional network involving corner- and edge-linkage between iron polyhedra, and corner-sharing between phosphorus tetrahedra and iron polyhedra...