Synthesis, IR spectra, and structures of double metaphosphates MNi(PO3)(3)(M = Na or K)

Double metaphosphates of the composition MNi(PO3)(3) (M = Na or K) were pre pared by spontaneous crystallization from melts in the M2O-P2O5-NiO system. Their thermal properties were studied, and the IR spectra were analyzed. T he complete X-ray structure analysis of the compounds synthesized was perfo rmed. The NaNi(PO3)(3) crystals are orthorhombic with the unit-cell paramet ers a = 13.781(2) Angstrom, b = 10.584(2) Angstrom, c = 9.873(1) Angstrom, sp. gr. Pcca. The KNi(PO3)(3) crystals belong to the sp. gr. R3 with the un it-cell parameters a = 10.076(2) Angstrom and c = 9.623(5) Angstrom. The st ructures of the studied phosphates are compared with the structures of the related compounds. (C) 2000 MAIK "Nauka/Interperiodica".