The synthesis and crystal structure of a hydrated magnesium phosphate Mg3(PO4)2·4H2O

The synthesis and crystal structure of a novel hydrated magnesium phosphate is described. The crystal structure was solved from powder X-ray diffraction data. Mg3(PO4)2·4H2O crystallizes in the orthorhombic space group Cmc21 (No. 36) with a=8.41087(9) Å, b=17.3850(2) Å, c=12.8034(1) Å, V=1872.15(4) Å3 and Z=8. The structure consists of sheets stacked along [010], which are linked by edge sharing octahedral Mg2O6(H2O)4 dimers. Within the sheets there are infinite edge-sharing chains of Mg octahedra along [100]. The compound has been further characterized by 31P MAS NMR spectroscopy and thermogravimetric analysis. The crystal structure of two dehydrated variants existing around 200 (Mg3(PO4)2·2.5H2O) and 275 °C (Mg3(PO4)2·2H2O) remain unknown.