The synthesis and crystal structure of a hydrated magnesium phosphate Mg_3(PO_4)_2 centre dot 4H_2O

摘要

The synthesis and crystal structure of a novel hydrated magnesium phosphate is described. The crystal structure was solved from powder X-ray diffraction data. Mg_3(PO_4)_2 centre dot 4H_2O crystallizes in the orthorhombic space group Cmc2_1 (No.36) with a = 8.41087(9) A, b = 17.3850(2) A, c = 12.8034(1) A, V = 1872.15(4) A~3 and Z = 8. The structure consists of sheets stacked along (010), which are linked by edge sharing octahedral Mg_2O_6(H_2O)_4 dimers. Within the sheets there are infinite edge-sharing chains of Mg octahedra along (100). The compound has been further characterized by ~(31)P MAS NMR spectroscopy and thermogravimetric analysis. The crystal structure of two dehydrated variants existing around 200 (Mg_3(PO_4)_2 centre dot 2.5H_2O) and 275 deg C (Mg_3(PO_4)_2 centre dot 2H_2O) remain unknown.