Besma Lajmi

Reinvestigation of the binary diagram Na3PO4–FePO4 and crystal structure of a new iron phosphate Na3Fe3(PO4)4

A new iron(III) phosphate Na{sub 3}Fe{sub 3}(PO{sub 4}){sub 4} has been synthesized and characterized. It decomposes before melting at 860 deg. C into FePO{sub 4} and Na{sub 3}Fe{sub 2}(PO{sub 4}){sub 3}. The structure of the compound was determined by single-crystal X-ray diffraction. The unit cell is monoclinic with the following parameters: a=19.601(8) A, b=6.387(1) A, c=10.575(6) A and {beta}=91.81(4) deg.; Z=4; space group: C2/c. Na{sub 3}Fe{sub 3}(PO{sub 4}){sub 4} exhibits a layered structure involving corner-linkage between FeO{sub 6} octahedra, and corner- and edge-sharing between FeO{sub 6} octahedra and PO{sub 4} tetrahedra. The Na{sup +} cations occupying the interlayer space are six- and seven-fold coordinated by oxygen atoms. The relationship between the structure of Na{sub 3}Fe{sub 3}(PO{sub 4}){sub 4} and the previous reported hydrate K{sub 3}Fe{sub 3}(PO{sub 4}){sub 4}{center_dot}H{sub 2}O will be discussed.

Crystal structure, magnetic properties and Mössbauer spectroscopy of NaCaFe3(PO4)4

Abstract A new sodium and calcium iron phosphate, NaCaFe 3 (PO 4 ) 4 , has been synthesized by a flux method and characterized by single crystal X-ray diffraction, magnetic susceptibility and Mossbauer spectroscopy. The compound crystallizes in the orthorhombic space group Pcab with the parameters a =8.706(4) A, b =9.410(1) A, c =29.211(6) A, V =2393 A 3 and Z =8. The structure consists of discrete FeO 6 octahedra and FeO 5 trigonal bipyramids, corner-sharing with PO 4 tetrahedra that form a [Fe 3 P 4 O 16 ] n three-dimensional framework with two distinct cavities which are the Na + and Ca 2+ sites. Mossbauer spectroscopy results confirm those obtained from X-ray diffraction. Magnetic susceptibility indicates an antiferromagnetic behavior with a Neel temperature T N ≈26 K.

The iron phosphate NaZnFe2(PO4)3

Crystals of sodium zinc diiron(III) triphosphate, NaZnFe(2)(PO(4))(3), have been synthesized and structurally characterized by single-crystal X-ray diffraction. The compound features a new structural type built up from ZnO(6) octahedra, FeO(6) octahedra and FeO(4) tetrahedra, linked together via the corners and edges of PO(4) tetrahedra to form a three-dimensional framework, with tunnels running along [100]. Within these tunnels, Na(+) cations occupy a highly distorted cubic site.

The iron phosphate K3Fe5(PO4)6

The crystal structure of tripotassium pentairon hexaphosphate has been determined by single-crystal X-ray diffraction. The structure contains one Fe atom on a center of symmetry, one K, two Fe and two P atoms on twofold axes, and one Fe, two P and one K atom in general positions. The K(3)Fe(5)(PO(4))(6) structure consists of a complex three-dimensional framework of corner-sharing between iron polyhedra, and corner- and edge-sharing between PO(4) tetrahedra and iron polyhedra (FeO(5) and FeO(6)). This linkage between iron and phosphorus forms intersecting channels containing the K atoms.