Original paper

BaYb6(Si2O7)2(Si3O10) ? the first silicate containing both Si2O7 and Si3O10 groups: synthesis, crystal chemistry and topology

Wierzbicka-Wieczorek, Maria; Kolitsch, Uwe

European Journal of Mineralogy Volume 25 Number 4 (2013), p. 509 - 517

published: Dec 20, 2013

DOI: 10.1127/0935-1221/2013/0025-2289

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Abstract

Colourless crystals of the novel compound BaYb6(Si2O7)2(Si3O10) were prepared using a high-temperature flux-growth technique in air. The crystal structure was solved and refined to R (F) = 2.50 % using single-crystal X-ray diffraction data collected at room temperature. The silicate is monoclinic, space group P21/m (Z = 2), with a = 5.5173(11), b = 27.260(6), c = 6.8150(14) Å, ? = 106.73(3), V = 981.6(3) Å3. BaYb6(Si2O7)2(Si3O10) represents the first silicate containing both (Si2O7) and (Si3O10) groups in the ratio 2:1 and is isotypic with (NH4)Cd6(P2O7)2(P3O10). Its framework topology is characterised by one horseshoe-shaped trisilicate (Si3O10) group, two symmetrically equivalent (Si2O7) groups with the Si?O?Si angle of 165.3 and staggered conformation, and zigzag chains of edge-sharing distorted YbO6 octahedra (). The Ba atoms occupy narrow channels extending parallel to [100]. The topological features of BaYb6(Si2O7)2(Si3O10) are compared to those of other compounds containing mixed groups (M 2O7) and (M 3O10). A similarity to BaY4(Si2O7)(Si3O10) is pointed out.

Keywords

barium ytterbium silicate • crystal structure • high-temperature flux synthesis • mixed sorosilicates • single-crystal x-ray diffraction