The crystal structures of three new complex silicates of scandium

Autor(en)

Maria Wierzbicka-Wieczorek, Uwe Kolitsch, Ekkehart Tillmanns

Abstrakt

Three new scandium silicates with framework structures made of octahedra and tetrahedra, KSrScSi2O7, NaBaScSi2O7 and RbBaScSi3O9, were obtained through a high-temp. flux-growth technique. Their crystal structures have been detd. from single-crystal intensity data (MoK.alpha. radiation, CCD area detector, 293 K; R(F) = 3.30, 1.82, 2.00%, resp.). The disilicate KSrScSi2O7 is monoclinic, P21/n, with a 9.446(2), b 5.478(1), c 12.537(3) .ANG., .beta. 104.39(3), V 628.4(2) .ANG.3, Z = 4. The disilicate NaBaScSi2O7 forms monoclinic crystals with space-group symmetry P21/m, with a 6.845(1), b 5.626(1), c 8.819(2) .ANG., .beta. 109.33(3), V 320.47(10) .ANG.3, Z = 2. The cyclosilicate RbBaScSi3O9 crystallizes as pseudohexagonal triplets; it is also monoclinic, P21/n, with a 6.957(1), b 10.199(2), c 11.881(2) .ANG., .beta. 90.07(3), V 843.0(2) .ANG.3, Z = 4. The topologies of KSrScSi2O7 and NaBaScSi2O7 show clear similarities, corresponding to isolated Si2O7 groups, bound to octahedrally coordinated Sc3+. The pseudohexagonal arrangement in RbBaScSi3O9 is based on isolated ScO6 octahedra, each of which is corner-linked to Si3O9 rings. In all three compds., the alkali and alk.-earth atoms occupy voids in the resulting three-dimensional frameworks. Results of a Raman spectroscopic study of the two disilicates and of five related novel disilicates are also briefly presented, with a focus on the behavior of the Si2O7 group.

Organisation(en)

Institut für Mineralogie und Kristallographie

Externe Organisation(en)

Naturhistorisches Museum Wien (NHM)

Journal

The Canadian Mineralogist

Band

48

Seiten

51-68

Anzahl der Seiten

18

ISSN

0008-4476

Publikationsdatum

2010

Peer-reviewed

Ja

ÖFOS 2012

105113 Kristallographie

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/302cf601-d782-49fb-b76c-1ae0a7c8242f