Synthesis and crystal structure of a new microporous silicate with a mixed octahedral-tetrahedral framework: Cs3ScSi8 O19
- Autor(en)
- Uwe Kolitsch, Ekkehart Tillmanns
- Abstrakt
During investigations of the System Sc2O3-Al 2O3-TiO2-SiO2, a new, unusual microporous compound, Cs3ScSi8O 19, was synthesized as colourless plates from a CsF-MoO3 flux. The crystal structure was determined from single-crystal X-ray diffraction data (Mo-Ka radiation, CCD area detector). The compound is orthorhombic, space group Pnma, with a = 11.286(2), b = 7.033(1), c = 26.714(5) A°, and Z = 4 (R1(F) = 2.6% and wR2a11(F2) = 7.3%, using 3066 'observed' reflections with Fo > 4s(Fo)). The crystal structure of Cs3ScSi8O19 represents a new microporous framework structure type ('MCV-1'), and the compound is exceptional in being the first representative of a mixed octahedral-tetrahedral framework structure, in which the [TO 4]:[MO6] ratio is >6:1. The structure is based on isolated, nearly regular ScO6 octahedra [d av(Sc-O) = 2.112 A°] sharing corners with SiO 4 tetrahedra to form an open framework with four-, six- and eight-membered rings; the latter are formed by SiO4 tetrahedra only. Two fully occupied Cs positions are located in large framework voids close to the six-membered rings, whereas four partly occupied and disordered Cs positions are close to very large framework voids bordered by the puckered eight-membered rings. The cavities are linked into channels parallel to [100] and [010]. The structure is compared with that of Cs2TiSi6O15 and related microporous scandium-, REE-, titano- and zirconosilicate minerals and compounds. Cs3ScSi8O19 or derivatives may be important in the context of immobilization of radioactive 137Cs waste, cationic conductivity or catalysis. Œ 2004 The Mineralogical Society.
- Organisation(en)
- Institut für Mineralogie und Kristallographie
- Journal
- Mineralogical Magazine
- Band
- 68
- Seiten
- 677-686
- Anzahl der Seiten
- 10
- ISSN
- 0026-461X
- Publikationsdatum
- 2004
- Peer-reviewed
- Ja
- ÖFOS 2012
- 1051 Geologie, Mineralogie
- Link zum Portal
- https://ucrisportal.univie.ac.at/de/publications/781a8df0-4a74-412a-8be1-c9e1a8772029