Na 1.85 Mg 1.85 in 1.15 (PO 4)3 and Ag 1.69 Mg 1.69 in 1.31 (PO 4)3 with alluaudite-type structures

Abstract

Single crystals of two new phosphates, sodium magnesium indium(III) tris(orthophosphate) and silver magnesium indium(III) tris(orthophosphate), were obtained from solid-state reactions. The two phosphates are isotypic and exhibit alluaudite-type structures. They are characterized by a cationic disorder of the Mg and In sites and a partial occupation of the Na and Ag sites, respectively. The structure of both phosphates is made up of chains of edge-sharing [(Mg,In)O 6] octahedra extending parallel to [10]. Adjacent chains are linked by PO 4 tetrahedra to form a three-dimensional framework delimiting two types of channels parallel to [001] in which the monovalent cations are situated. The coordination numbers of the Na + cations are 6 and 8, and for both Ag + cations 6. The corresponding coordination spheres are considerably distorted.