K0.53Mn2.37Fe1.24(PO4)3

During an attempt to crystallize potassium manganese diiron phosphate KMnFe2(PO4)3 by the flux method, a new phase, potassium dimanganese iron triphosphate, K0.53Mn2.37Fe1.24(PO4)3, was isolated. This phase, whose composition was confirmed by ICP analysis, is isotypic with the alluaudite-like phosphates, thus it exhibits the (A2)(A′2)(A1)(A′1)(A′′1)(M1)(M2)2(PO4)3 general formula. The site occupancies led to the following cation distribution: 0.53 K on A′2 (site symmetry 2), 0.31 Mn on A′′1, 1.0 Mn on M1 (site symmetry 2) and (0.62 Fe + 0.38 Mn) on M2. The structure is built up from infinite chains of edge-sharing M1O6 and M2O6 octahedra. These chains run along [10] and are connected by two different PO4 tetrahedra, one of which exhibits 2 symmetry. The resulting three-dimensional framework delimits large tunnels parallel to [001], which are partially occupied by the K+ and Mn2+ cations.

[1]  A. Wattiaux,et al.  Structural investigation of the alluaudite-like mixed-valence iron phosphate: Na1.25Mg1.10Fe1.90(PO4)3 , 2008 .

[2]  S. Parkin,et al.  XABS2: an empirical absorption correction program , 1995 .

[3]  P. Tarte,et al.  Synthese et cristallochimie de NaCaCdMg 2 (PO 4 ) 3 , phosphate nouveau a structure alluaudite sans cation trivalent , 1995 .

[4]  Giovanni Luca Cascarano,et al.  Completion and refinement of crystal structures with SIR92 , 1993 .

[5]  C. Pico,et al.  Neutron diffraction, Mössbauer spectrum, and magnetic behavior of Ag2FeMn2(PO4)3 with alluaudite-like structure , 2001 .

[6]  Jacques Darriet,et al.  Characterization by X-ray diffraction, magnetic susceptibility and Mössbauer spectroscopy of a new alluaudite-like phosphate:: Na4CaFe4(PO4)6 , 2004 .

[7]  G. Stucky,et al.  Synthesis of open-framework transition-metal phosphates using organometallic precursors in acidic media. Preparation and structural characterization of Fe5P4O20H10 and NaFe3P3O12 , 1986 .

[8]  W. Schmahl,et al.  Combined X-ray Rietveld, infrared and Raman study of a new synthetic variety of alluaudite, NaCdIn2(PO4)3 , 1993 .

[9]  W. H. Baur.  The geometry of polyhedral distortions. Predictive relationships for the phosphate group , 1974 .

[10]  D. Seo,et al.  Structural and Electronic Factors Governing the Metallic and Nonmetallic Properties of the PyrochloresA2Ru2O7−y , 1997 .

[11]  G. Sheldrick.  A short history of SHELX. , 2008, Acta crystallographica. Section A, Foundations of crystallography.

[12]  R. D. Shannon.  Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides , 1976 .

[13]  I. D. Brown,et al.  Bond‐valence parameters obtained from a systematic analysis of the Inorganic Crystal Structure Database , 1985 .

[14]  A. Driss,et al.  The alluaudite-like phosphate Na1.79Mg1.79Fe1.21(PO4)3 , 2003 .