Structural features of the oxidonitridophosphates K3MIII(PO3)3N (MIII= Al, Ga)

Abstract

Cubic crystals of tripotassium aluminium (or gallium) nitridotriphosphate, K3MIII(PO3)3N (MIII= Al, Ga), were grown by application of the self-flux method. In their isostructural crystal structures, all metal cations and the N atom occupy special positions with site symmetry 3, while the P and O atoms are situated in general positions. The three-dimensional framework of these oxidonitridophosphates is built up from [M IIIO6] octa hedra linked together via (PO3)3N groups. The latter are formed from three PO3N tetra hedra sharing a common N atom. The coordination environments of the three potassium cations are represented by two types of polyhedra, viz. KO9for one and KO9N for the other two cations. An unusual tetra dentate type of coordination for the latter potassium cations by the (PO3)3N6-anion is observed. These K3MIII(PO3)3N (MIII= Al, Ga) compounds are isostructural with the Na3M III(PO3)3N (M III= Al, V, Ti) compounds.