One-pot synthesis, X-ray diffraction and MAS NMR spectroscopic study of gallosilicate nitrate cancrinite Na8[GaSiO4]6(NO3)4(H2O)6

Abstract

One-pot synthetic gallosilicate nitrate cancrinite (CAN) framework topology have been synthesized under hydrothermal conditions at 100°C. The synthesized product was characterized by, X-ray powder diffraction, IR, Raman and 29Si, 23Na MAS NMR spectroscopy, SEM and thermogravimetry. The crystal structure refinement of pure nitrate cancrinite has been carried out from X-ray data using Rietveld refinement method. Gallosilicate cancrinite Na8[GaSiO4]6(NO3)4(H2O)6 crystalline hexagonal with space group P63 and a = 12.77981 Å (2), c = 5.20217 Å (1), (Rwp = 0.0696 Rp = 0.0527). The results by MAS NMR spectroscopy confirmed the alternating Si, Ga ordering of the gallosilicate framework for a Si/Ga ratio of 1.0. A distribution of the quadrupolar interaction of the sodium cations caused by the enclatherated water molecules and motional effects can be suggested from the 23Na MAS NMR. Thermogravimetric investigation shows the extent of nitrate entrapment, stability within the cancrinite cage and decomposition properties. SEM clearly shows the hexagonal needle shaped crystals of nitrate cancrinite.