The crystal chemistry of iron (III) monophosphates with mono and divalent metallic cations

Abstract

Abstract.As a contribution to the study of alkaline iron (III) monophosphates, we recently investigated the A 3 PO 4 -M 3 (PO 4 ) 2 -FePO 4 (A: alkali metal; M: divalent cation) using both the flux method and the solid state reaction. This investigation led to the synthesis and structural characterization of twelve new compounds. Their structural analysis showed them to be constructed by PO 4 tetrahedra and FeO x polyhedra (x = 6, 5, 4). The Fe polyhedra are either isolated or forming finite units of corner-or edge-sharing, or infinite chains of edge-sharing octahedra. The resulting Fe structural units are linked by the PO 4 tetrahedra via corner or edge-sharing, giving rise to mixed covalent frameworks which can be either bi-or three-dimentionnel. The alkali cations occupy the interlayer space or tunnels and cavities.