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Raman and IR spectroscopic studies of alunite-supergroup compounds containing AI, Cr3+, Fe3+ and V3+ at the B site

Murphy, P.J. and Smith, Adrian M.L. and Hudson-Edwards, Karen A. and Dubbin, W.E. and Wright, K. (2009) Raman and IR spectroscopic studies of alunite-supergroup compounds containing AI, Cr3+, Fe3+ and V3+ at the B site. Canadian Mineralogist 47 (3), pp. 663-681. ISSN 0008-4476.

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Official URL: http://dx.doi.org/10.3749/canmin.47.3.663

Abstract

Raman and IR spectroscopies, X-ray diffraction and chemical analysis have been used to characterize synthetic compounds of the alunite supergroup of formula AB3(SO4)2(OH)6, with A = Na+, K+, H3O+ and B = Al, Cr3+, Fe3+, V3+. For each A-site cation, the proportion of B-site vacancies decreases in the same order as the effective ionic radius of the B-site cations (Al > Cr > Fe > V). Raman and IR spectra of the compounds with B = Al and Fe3+ (alunite- and jarosite-group phases) show very close agreement with previously published spectra. The spectra for Cr- and V-based analogues show similarities to the alunite- and jarosite-group phases, and particularly the latter. The Raman and IR spectra are similar in the high-wavenumber ranges (around 3400–3500 cm–1), but are different in the intermediate and, particularly, the lower ranges, <700 cm–1, probably owing to the different responses of Raman and IR to SO4 and metal–O (M–O) group symmetries. The a parameter correlates well with {nu}1SO4, {nu}2SO4 and {nu}4SO4 Raman and {nu}4SO4 IR wavenumbers. There are differences in the OH-stretching regions, and shifts in the main {nu}SO4 and M–O peaks of the alunite-group phases, and Cr-, Fe- and V-based analogues with substitution of K, Na or H3O at the A site in the Raman and IR spectra. Raman and IR spectroscopies are therefore useful in distinguishing these compounds.

Item Type: Article
Keyword(s) / Subject(s): alunite supergroup, jarosite group, chromium, vanadium, Raman, infrared spectra, X-ray diffraction
School or Research Centre: Birkbeck Schools and Research Centres > School of Science > Earth and Planetary Sciences
Depositing User: Administrator
Date Deposited: 09 Feb 2011 09:34
Last Modified: 17 Apr 2013 12:18
URI: http://eprints.bbk.ac.uk/id/eprint/1800

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