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Temperature‐dependent Raman scattering studies of Na 2 MoO 4
Author(s) -
Saraiva G. D.,
Paraguassu W.,
Maczka M.,
Freire P. T. C.,
Lima J. A.,
Paschoal C. W. A.,
Mendes Filho J.,
Souza Filho A. G.
Publication year - 2008
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1942
Subject(s) - orthorhombic crystal system , raman spectroscopy , phase transition , tetrahedron , crystal structure , chemistry , raman scattering , lattice (music) , crystallography , ion , bond length , phonon , anhydrous , atmospheric temperature range , condensed matter physics , thermodynamics , physics , optics , organic chemistry , acoustics
The mode assignment of the cubic phase of anhydrous Na 2 MoO 4 was carried out on the basis of lattice dynamic calculation using the classical rigid‐ion model. Temperature‐dependent studies indicate that this crystal remains in the cubic structure in the 15–773 K range and undergoes a phase transition at around 783 K. The behavior of the Raman modes indicates that this transition is strongly first‐order in nature and the phase above 773 K may have an orthorhombic symmetry. This transition is connected with tilting and/or rotations of the MoO 4 tetrahedra, which lead to a disorder at the MoO 4 sites. Our results give also evidence that the MoO bond lengths decrease in the high‐temperature phase. Copyright © 2008 John Wiley & Sons, Ltd.