Structural studies on a high-pressure polymorph of NaYSi{sub 2}O{sub 6}
- Institute of Mineralogy and Petrography, University of Innsbruck, Innrain 52, A-6020 Innsbruck (Austria)
High-pressure synthesis experiments in the system Na{sub 2}O-Y{sub 2}O{sub 3}-SiO{sub 2} revealed the existence of a previously unknown polymorph of NaYSi{sub 2}O{sub 6} or Na{sub 3}Y{sub 3}[Si{sub 3}O{sub 9}]{sub 2} which was quenched from 3.0 GPa and 1000 deg. C. Structural investigations on this modification have been performed using single-crystal X-ray diffraction data collected at ambient conditions. Furthermore, unpolarized micro-Raman spectra have been obtained from single-crystal material. The high-P modification of NaYSi{sub 2}O{sub 6} crystallizes in the centrosymmetric space group C2/c with 12 formula units per cell (a=8.2131(9) A, b=10.3983(14) A, c=17.6542(21) A, {beta}=100.804(9){sup o}, V=1481.0(3) A{sup 3}, R(|F|)=0.033 for 1142 independent observed reflections) and belongs to the group of cyclo-silicates. Basic building units are isolated three-membered [Si{sub 3}O{sub 9}] rings located in layers parallel to (010). Within a single layer the rings are concentrated in strings parallel to [100]. The sequence of directedness of up (U) or down (D) pointing tetrahedra of a single ring is UUU or DDD, respectively. Stacking of the layers parallel to b results in the formation of a three-dimensional structure in which yttrium and sodium cations are incorporated for charge compensation. In more detail, four non-tetrahedral cation positions can be differentiated which are coordinated by 6 and 8 oxygen ligands. Refinements of the site occupancies did not reveal any indication for mixed Na-Y populations on these positions. Finally, several geometrical parameters of rings occurring in cyclo-trisilicate structures have been compiled and are discussed. - Graphical abstract: Projection of the whole structure of high-P NaYSi{sub 2}O{sub 6} parallel to [100].
- OSTI ID:
- 21015857
- Journal Information:
- Journal of Solid State Chemistry, Vol. 180, Issue 6; Other Information: DOI: 10.1016/j.jssc.2007.04.021; PII: S0022-4596(07)00176-4; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
Similar Records
The crystal structure determinations and refinements of K{sub 2}S{sub 2}O{sub 7}, KNaS{sub 2}O{sub 7} and Na{sub 2}S{sub 2}O{sub 7} from X-ray powder and single crystal diffraction data
U(IV)/Ln(III) mixed site in polymetallic oxalato complexes. Part III: Structure of Na[Yb(C{sub 2}O{sub 4}){sub 2}(H{sub 2}O)].3H{sub 2}O and the derived quadratic series (NH{sub 4}{sup +}){sub 1-x}[Ln{sub 1-x}U{sub x} (C{sub 2}O{sub 4}){sub 2}(H{sub 2}O)].(3+x) H{sub 2}O, Ln=Y, Pr-Sm, Gd, Tb