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In‐situ high temperature Raman spectroscopic study on the structural evolution of Na 2 W 2 O 7 from the crystalline to molten states
Author(s) -
Wang J.,
You J. L.,
Sobol A. A.,
Lu L. M.,
Wang M.,
Wu J.,
Lv X. M.,
Wan S. M.
Publication year - 2017
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.5036
Subject(s) - raman spectroscopy , tungstate , tungsten , octahedron , quenching (fluorescence) , crystallography , crystal (programming language) , phase (matter) , crystal structure , ion , materials science , chemistry , analytical chemistry (journal) , inorganic chemistry , metallurgy , physics , organic chemistry , chromatography , optics , programming language , quantum mechanics , computer science , fluorescence
In order to optimize the growth conditions for tungstate crystals, the structural evolution of ditungstate Na 2 W 2 O 7 from the crystalline to molten states during heating has been investigated by in‐situ high temperature Raman spectroscopic technique. The experimental temperature‐dependent Raman spectra showed that Na 2 W 2 O 7 crystal has not undergone any solid‐state phase transformations during heating process from 298 to 1013 K. In contrast to crystalline Na 2 W 2 O 7 , in which [WO 4 ] tetrahedra and [WO 6 ] octahedra coexist, the tungsten–oxygen groups in molten Na 2 W 2 O 7 have the form of (W 2 O 7 ) 2− anion composed of two [WO 4 ] by sharing their corner oxygen atoms. To validate the structural evolution of Na 2 W 2 O 7 above, Raman activity of vibrations of Na 2 W 2 O 7 crystal and its melt were calculated using density functional theory (DFT) and compared with the in‐situ Raman spectra of Na 2 W 2 O 7 . A non‐crystalline phase and an intermediate state of Na 2 W 2 O 7 were obtained by rapid quenching and relatively slow cooling of the homogeneous melt, respectively. Copyright © 2016 John Wiley & Sons, Ltd.