Structure and 31P NMR spectroscopy of a new phosphate, Na8Ca1.5Mg12.5(PO4)12.

A new phosphate, sodium calcium magnesium tetrakis(phosphate), Na(8)Ca(1.5)Mg(12.5)(PO(4))(12), has been synthesized by a flux method. Its novel structure consists of MgO(x) (x = 5 and 6) polyhedra and MO(7) (M = Mg or Na) octahedra linked directly through common corners or edges to form a rigid three-dimensional skeleton, reinforced by corner-sharing between identical Mg(12)MO(48) units. The connection of these units by the PO(4) tetrahedra induces cavities and crossing tunnels where the Na(+) and Ca(2+) cations are located. This structural model was supported by a (31)P NMR spectroscopy study which confirmed the existence of 12 crystallographically independent sites for the P atoms.