SYNTHESIS, STRUCTURE, AND CHARACTERIZATION OF HALATE SODALITES - M(8)[ALSIO4](6)(XO(3))(X)(OH)(2-X) M=NA, LI, OR K, X=CL, BR, OR I

The halate sodalites of the compositions Na-8[AlSiO4](6)(ClO3)(1.91)(OH)(0.09) and Na-8[AlSiO4](6)(BrO3)(1.77)(OH)(0.23) have been prepared using low-temperature solution syntheses and the derivatives Na4.7Li3.3[AlSiO4](6)(ClO3)(1.91)(OH)(0.09), Na3.5K4.5[AlSiO4](6)(ClO3)(1.91)(OH)(0.09)Na3.3Li4.7[AlSiO4](6)(BrO3)(1.77)(OH)(0.23) and Na3.3K4.7[AlSiO4](6)(BrO3)(1.77)(OH)(0.23) obtained by aqueous cation exchange. All products crystallize with the cubic sodalite structure in the space group P43n. Rietveld profile refinement has been completed from powder neutron diffraction data collected at 4 and 300 K revealing a structure similar to that found for perchlorate sodalite, with the anion positioned slightly off the cage center. Infrared and Raman spectroscopy has verified the presence of the halate anions within the beta-cage, and Si-29 MAS n.m.r. has confirmed that the framework ordering is consistent with the space group. Thermogravimetric analyses have provided information on the extent of halate entrapment, stability within the cage, and decomposition properties.