Novel synthetic alkali-yttrium silicates with a new microporous mixed framework topology: (Rb,Cs)9Y7Si24O63 and isotypic Rb9Y7Si24O63

Prismatic colourless crystals of the two novel, isotypic title compounds were obtained by the flux growth technique. The crystal structures have been determined from single-crystal intensity data in space group R anti 3 with a=28.819(4)/28.799(4), c=13.916(3)/13.864(3) A, V=10009(3)/9958(3) A3, Z=6, R(F) =4.99/6.44%, respectively. They represent a novel structure type with microporous character. The framework is built from six-membered silicate rings (approximate UDUDUD orientation) containing isolated YO6 octahedra and compressed ''six-membered rings'', which in fact build a spiral of corner-sharing SiO4 tetrahedra. Approximately parallel to[111] run two different irregular channels hosting the Rb/Cs and Rb atoms. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)