Small-pore framework zirconium and hafnium silicates with the structure of mineral tumchaite


Small-pore framework sodium silicates (AV-14) Na2MSi4O11 (.) 2H(2)O (M = Zr and Hf) possessing the structure of the rare mineral tumchaite have been prepared via hydrothermal synthesis. The AV-14 framework consists of corner-sharing MO6 (M = Zr, Hf) octahedra and SiO4 tetrahedra. The [Si4O11] Silicate sheets may be described as a combination of the spiral chains formed from the corner-sharing SiO4 tetrahedra. These sheets are connected by MO6 octahedra, resulting in a three dimensional framework. AV-14 materials are the first examples of synthetic microporous zirconium and hafnium silicates whose structures are built up from silicate sheets. Hf- and Zr-AV-14 materials and the parakeldyshite-type phase, which forms at 1100 degreesC from the decomposition of Zr-AV-14, have been studied by bulk chemical analysis, powder X-ray diffraction, scanning electron microscopy, Na-23 and Si-29 magic-angle spinning NMR spectroscopy and thermogravimetry. (C) 2004 Elsevier Inc. All rights reserved.




Chemistry; Science & Technology - Other Topics; Materials Science


Lin, Z; Rocha, J

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