The title compound, Na2Co2Fe(PO4)3, was synthesized by a solid-state reaction. This new stoichiometric phase crystallizes in an alluaudite-like structure. In this structure, all atoms are in general positions except for four atoms which are located at the special positions of the C2/c space group. One Co atom, one P and one Na atom are all located on Wyckoff position 4e (2), while the second Na atom is located on an inversion centre 4a (-1). The other Co and Fe atoms occupy a general position with a statistical distribution. The open framework results from [(Co,Fe)2O10] units of edge-sharing [(Co,Fe)O6] octahedra, which alternate with [CoO6] octahedra that form infinite chains running along the [10-1] direction. These chains are linked together through PO4 tetrahedra by the sharing of vertices so as to build layers perpendicular to . The three-dimensional framework is accomplished by the stacking of these layers, leading to the formation of two types of tunnels parallel to  in which the Na+ cations are located, each cation being surrounded by eight O atoms.
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Document Type: Research Article
Laboratoire de Chimie du Solide Appliquée, Faculté des Sciences, Université Mohammed V, Avenue Ibn Battouta, BP 1014, Rabat, Morocco
Département de chimie, Faculté des Sciences, Université des Sciences et Techniques de Masuku, BP 943, Franceville, Gabon
January 1, 2015