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

A new phosphate, sodium calcium magnesium tetrakis(phosphate), Na₈Ca_1.5Mg_12.5(PO₄)₁₂, has been synthesized by a flux method. Its novel structure consists of MgO_x (x = 5 and 6) polyhedra and MO₇ (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 Mg₁₂MO₄₈ units. The connection of these units by the PO₄ tetrahedra induces cavities and crossing tunnels where the Na⁺ and Ca²⁺ cations are located. This structural model was supported by a ³¹P NMR spectroscopy study which confirmed the existence of 12 crystallographically independent sites for the P atoms.