Synthesis and characterization of a new iron phosphate KSrFe2(PO4)3 with a langbeinite type structure

Synthesis, crystal structure, Mössbauer spectroscopy and magnetic susceptibility of a new phosphate KSrFe2(PO4)3 are described. This compound crystallizes with the unit cell parameter a = 9.809(2) Å of the cubic space group P213 and four formula units per cell. Its structure belongs to the well known langbeinite type. It consists of a 3D framework resulting from a corner-sharing between FeO6 octahedra and PO4 tetrahedra. This framework delimits two distinct cavities, statistically occupied by the K+ and Sr2+ ions. The Mössbauer spectroscopy gave clear evidence of the exclusive presence of octahedral Fe3+ ions. The magnetic susceptibility measurements revealed that the compound follows the Curie–Weiss behavior with an experimental effective moment per unit formula μ = 8.16 μB, consistent with the ideal spin only value of 8.37 μB.