Crystal structure and Mössbauer spectroscopy of a new iron phosphate Mg2.88Fe4.12(PO4)6

[Display omitted] •This study reports the synthesis and characterization of a new iron phosphate.•The cationic distribution is supported by a Mössbauer spectroscopy study.•The magnetic susceptibility results are discussed. A new mixed valence iron phosphate Mg2.88Fe4.12(PO4)6 has been prepared as single crystals by the flux method and as a powder by solid state reaction and its crystal structure has been determined by X-ray diffraction. This compound crystallises in the triclinic system with space group P1¯ and a=6.325(5)Å, b=7.911(3)Å, c=9.271(3)Å, α=104.62(1)°, β=108.41(1)° and γ=101.24(1)° and Z=1. Its structure is similar to that of the mineral howardevansite. It consists of Fe2O10 bioctahedral units and MgO5 trigonal bipyramids sharing edges to form infinite zigzag chains. Such chains are linked to each other by MO6 (0.88Mg2++0.12Fe2+) octahedra and PO4 tetrahedra resulting in a 3D covalent framework. Magnetic measurements indicated two successive transitions at 46K and 22K. Mössbauer spectroscopy confirmed the mixed valence of iron and gave accurate information about its local environment.