Disordered but primitive gallosilicate hydro-sodalite: Structure and thermal behaviour of a framework with novel cation distribution

Abstract

The structure of a new gallosilicate sodalite |Na6.16(1)(H2O)8|[Ga1.04(1)Si0.96(1)O4]6 described in space group 4 ̅ 3 with lattice parameter a = 885.208(7) pm is reported. For such a sodalite with a deviation from a 1:1 ratio in the framework cations a body-centred structure in space group 4 ̅ 3 could be expected. The structure shows structural stress resulting from this unusual substitution by a high strain visible in reflections which are forbidden by symmetry in 4 ̅ 3. Distinct amounts of Ga and Si are redistributed on the opposite crystallographic position. The second coordination sphere of Si was examined by 29 Si MAS NMR, the absence of OHin the sodalites cages was checked by FTIR-and Raman spectroscopy. The intensity distribution of MAS NMR signal is modelled using a new technique to calculate the framework metal second neighbour coordination. The confirmed distribution leads to a low thermal stability of the cubic sodalite indicated by a new intermediated phase which could be regarded as a triclinic distorted cancrinite with three-time increased c lattice parameter. This intermediate phase decomposes at around 1000 K to a beryllonite-type sodium gallosilicate.

On the thermal stability of manganese(II) sulfate and its reaction with zeolite A to form the sodalite Na6Mn2[Al6Si6O24](SO4)2

“…Na 6 Mn 2 [Al 6 Si 6 O 24 ](SO 4 ) 2 as a monophasic material through the reaction between anhydrous MnSO 4 and zeolite A at 620 °C in a closed system. Furthermore, it should be informative to analyse pristine Na 6 Mn 2 [Al 6 Si 6 O 24 ](SO 4 ) 2 using 29 Si MAS NMR to help resolve the issue of Si-Al ordering, since this has been applied by certain workers to other sodalites[26].Our results suggest it should be possible to substitute other divalent tetrahedrally coordinated cations with ionic radii between 73−93 pm, for example Cd 2+ and Fe 2+ , for Ca 2+ in haüyne, Na 6 Ca 2 [Al 6 Si 6 O 24 ](SO 4 ) 2 by the method described in this paper, so long as the divalent metal sulfate is thermally stable under stagnant air at the temperature that is high enough for it to react with zeolite A.…”