Intralamellar structural modifications related to the proton exchanging in K4Nb6O17 layered phase

Intralamellar structural modifications related to the proton exchanging in K4Nb6O17 layered phase

Author Bizeto, M. A. Autor UNIFESP Google Scholar
Leroux, F. Google Scholar
Shiguihara, A. L. Google Scholar
Temperini, M. L. A. Google Scholar
Sala, O. Google Scholar
Constantino, V. R. L. Google Scholar
Institution Univ Clermont Ferrand
Universidade Federal de São Paulo (UNIFESP)
Universidade de São Paulo (USP)
Abstract Basic structural aspects about the layered hexaniobate of K4Nb6O17 composition and its proton-exchanged form were investigated mainly by spectroscopic techniques. Raman spectra of hydrous K4Nb6O17 and H2K2Nb6O17 center dot H2O show significant modifications in the 950-800 cm(-1) region (Nb-O stretching mode of highly distorted NbO6 octahedra). the band at 900 cm(-1) shifts to 940 cm(-1) after the replacement of K+ ion by proton. Raman spectra of the original materials and the related deuterated samples are similar suggesting that no isotopic effect occurs. Major modifications were observed when H2K2Nb6O17 was dehydrated: the relative intensity of the band at 940 cm(-1) decreases and new bands seems to be present at about 860-890 cm(-1). the H+ ions should be shielded by the hydration sphere what preclude the interaction with the layers. Removing the water molecules, H+ ions can establish a strong interaction with oxygen atoms, decreasing the bond order of Nb-O linkage. X-ray absorption near edge structure studies performed at Nb K-edge indicate that the niobium coordination number and oxidation state remain identical after the replacement of potassium by proton. From the refinement of the fine structure, it appears that the Nb-Nb coordination shell is divided into two main contributions of about 0.33 and 0.39 nm, and interestingly the population, i.e., the number of backscattering atoms is inversed between the two hexaniobate materials. 2009 Elsevier B.V. All rights reserved.
Keywords Inorganic compounds
Raman spectroscopy
Language English
Date 2010-04-01
Published in Journal of Physics and Chemistry of Solids. Oxford: Pergamon-Elsevier B.V., v. 71, n. 4, p. 560-564, 2010.
ISSN 0022-3697 (Sherpa/Romeo, impact factor)
Publisher Elsevier B.V.
Extent 560-564
Origin http://dx.doi.org/10.1016/j.jpcs.2009.12.036
Access rights Closed access
Type Article
Web of Science ID WOS:000277055400037
URI http://repositorio.unifesp.br/handle/11600/32420

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