SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF MICROPOROUS YTTRIUM AND CALCIUM SILICATES

The synthesis and structural characterization of AV-1 (Aveiro micropor ous solid no. 1), the first synthetic microporous yttrium silicate con taining stoichiometric amounts of framework sodium (and yttrium) catio ns, are reported. AV-1, Na2K2Y2Si16O38. 10H(2)O, possesses the structu re of the rare mineral montregianite. The synthesis and structural cha racterization of AV-2, an alkali calcium silicate hydrate (ideal compo sition HKCa2Si8O19.6H2O) analogue of the rare mineral rhodesite, are a lso reported. The structures of AV-1 and AV-2 are characterized by the same type of double silicate layers, but important differences exist with respect to the constitution of the octahedral layers and channel species. AV materials have been characterized by a range of techniques , viz., scanning electron microscopy (SEM), powder X-ray diffraction ( XRD), Si-29 and Na-23 single- and triple-quantum (3Q) magic-angle spin ning (MAS) NMR spectroscopy, Fourier transform spectroscopy (FTIR), an d thermogravimetric analysis (TGA).