Characterization of cancrinite synthesized in 1,3-butanediol by Rietveld analysis of powder neutron diffraction data and solid-state 23Na NMR spectroscopy

The framework structure and extraframework atoms of calcined and dehydrated cancrinite synthesized in 1,3-butanediol are characterized by powder neutron diffraction and Na-23 nuclear magnetic resonance (NMR) spectroscopy. The cancrinite structure is refined in the hexagonal space group P6(3) (No. 173) with lattice parameters a = 12.659 Angstrom and c = 5.153 Angstrom. Carbonate anions are found occluded in the pores of the cancrinite structure. Although there are two different crystallographic cation sites found by the Rietveld refinement, there are three peaks in the Na-23 magic-angle spinning (MAS) NMR spectrum. These peaks correspond to sodium cations found in site I inside the cancrinite cages, cations in site II inside the cancrinite pore without neighboring carbonates, and cations in site II with neighboring carbonates. Quadrupole coupling constants (QCC) obtained by a simple point-charge model agree well with the simulation of the Na-23 MAS NMR spectra. (C) 1999 Elsevier Science B.V. All rights reserved.