Synthesis and crystal structure of a new magnesium phosphate Na₃RbMg₇(PO₄)₆

A new magnesium phosphate, Na₃RbMg₇(PO₄)₆ [tris-odium rubidium hepta-magnesium hexakis(ortho-phosphate)], has been synthesized as single crystals by the flux method and exhibits a new structure type. Its original structure is built up from MgO (x = 5 and 6) polyhedra linked directly to each other through common corners or edges and reinforced by corner-sharing with PO₄ tetra-hedra. The resulting anionic three-dimensional framework leads to the formation of channels along the [010] direction, in which the Na⁺ cations are located, while the Rb⁺ cations are located in large inter-stitial cavities.