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Crystal structure and thermal behaviour of (Rb,Cs)BSi 2 O 6 solid solutions
Author(s) -
Krzhizhanovskaya M. G.,
Bubnova R. S.,
Filatov S. K.,
Meyer D. C.,
Paufler P.
Publication year - 2006
Publication title -
crystal research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0232-1300
DOI - 10.1002/crat.200510575
Subject(s) - rietveld refinement , phase transition , crystal structure , solid solution , atmospheric temperature range , chemistry , phase (matter) , powder diffraction , crystallography , thermal expansion , diffraction , lattice constant , lattice (music) , analytical chemistry (journal) , materials science , thermodynamics , optics , physics , organic chemistry , metallurgy , acoustics
The crystal chemistry of Rb‐Cs boroleucites has been studied by means of X‐ray powder diffraction at room and elevated temperatures. The cubic I‐43d → cubic Ia3d phase transition was investigated using a series of samples prepared by solid‐state reaction along the pseudobinary system RbBSi 2 O 6 ‐ CsBSi 2 O 6 . The Rietveld refinement of the structures of Rb 1‐x Cs x BSi 2 O 6 solid solutions (x = 0.2, 0.4, 0.6, 0.8) demonstrates that the solutions with a high Rb content crystallise in the cubic I‐43d space group, and the boroleucites with a considerable Cs content have Ia3d symmetry. Rb can substitute Cs in a wide range of compositions. Within a narrow range of x = 0.5 ‐ 0.6 immiscibility was revealed. Under Rb‐Cs substitution the cubic lattice parameter, the (Rb,Cs)‐O distances, and the angles between tetrahedra of the I‐43d phase change clearly, while those of the Ia3d phase change slightly. The HTXRD data shows that the I‐43d phase transforms into a Ia3d phase on heating analogously to a change of the composition. As the Cs content increases the transition temperature decreases. The low temperature I‐43d phase shows a higher thermal expansion than the high temperature Ia3d phase. © 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim