Synthesis and structural study of a new iron phosphate K3Fe(PO4)2

Single crystals of a new iron monophosphate K3Fe(PO4)2 were synthesized by the flux method and characterized by X-ray diffraction, magnetic susceptibility and Mössbauer spectroscopy. The compound crystallizes in the monoclinic system with the space group P21/n and the parameters a=9.598(3)Å, b=11.086(2)Å, c=15.462(3)Å, β=90.30(2)° and Z=8. The crystal structure can be described in terms of [Fe2P4O17]∞ chains of FeO6 octahedra and PO4 tetrahedra sharing corners and edges. Adjacent chains are linked through common corners to form a three-dimensional framework containing crossing tunnels where the K+ ions are located. The magnetic measurements showed the compound to be antiferromagnetic with TN≈9K. The Mössbauer spectroscopy confirmed the occurrence of octahedral Fe3+ ions in a high spin state.