Raman and ir spectroscopic studies of alunite-supergroup compounds containing Al, Cr3+, Fe3+ AND V3+ at the B site

Pamela J. Murphy, Adrian M. L. Smith, Karen A. Hudson-Edwards, William E. Dubbin, Kate Wright

Research output: Contribution to journalArticlepeer-review

40 Citations (Scopus)

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, Cr 3+, 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-0 (M-O) group symmetries. The a parameter correlates well with v1SO4, v2SO4 and v4SO4 Raman and v4SO4 IR wavenumbers. There are differences in the OH-stretching regions, and shifts in the main vSO4 and -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.

Original languageEnglish
Pages (from-to)663-681
Number of pages19
JournalCanadian Mineralogist
Volume47
Issue number3
DOIs
Publication statusPublished - Jun 2009
Externally publishedYes

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