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Structural elucidation of β‐(Y,Sc) 2 Si 2 O 7 : combined use of 89 Y MAS NMR and powder diffraction
Author(s) -
Allix M.,
Alba M. D.,
Florian P.,
FernandezCarrion A. J.,
Suchomel M. R.,
Escudero A.,
Suard E.,
Becerro A. I.
Publication year - 2011
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889811021303
Subject(s) - crystallography , neutron diffraction , magic angle spinning , space group , crystal structure , group (periodic table) , magic angle , x ray crystallography , diffraction , chemistry , materials science , physics , nuclear magnetic resonance spectroscopy , stereochemistry , optics , organic chemistry
Although the structures of pure Sc 2 Si 2 O 7 and β‐Y 2 Si 2 O 7 have been described in the literature using the C 2/ m space group, 29 Si magic angle spinning (MAS) NMR measurements of the intermediate members of the Sc 2 Si 2 O 7 –β‐Y 2 Si 2 O 7 system indicate a lowering of the symmetry to the C 2 space group. Indeed, these compositions exhibit a unique Si crystallographic site and an Si—O—Si angle lower than 180°, incompatible with the C 2/ m space group. C 2 is the only possible alternative. Space group Cm can be discarded with regard to its two different Si sites per unit cell. Moreover, 89 Y MAS NMR data have revealed the existence of two different Y sites in the structure of the intermediate members of the Sc 2 Si 2 O 7 –β‐Y 2 Si 2 O 7 system, confirming the lowering of the symmetry to the C 2 space group. The viability of the C 2 model has therefore been tested and confirmed by refinement of synchrotron and neutron powder diffraction data for the different members of the system. The structural evolutions across the Sc 2 Si 2 O 7 –β‐Y 2 Si 2 O 7 system are discussed.