SEM, EDX and vibrational spectroscopic study of the phosphate mineral ushkovite MgFe3+2(PO4)2(OH)2·8H2O: Implications of the molecular structure

López, Andrés, Scholz, Ricardo, Frost, Ray L., & Belotti, Fernanda M. (2015) SEM, EDX and vibrational spectroscopic study of the phosphate mineral ushkovite MgFe3+2(PO4)2(OH)2·8H2O: Implications of the molecular structure. Journal of Molecular Structure, 1081, pp. 329-333.

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The mineral ushkovite has been analyzed using a combination of electron microscopy with EDX and vibrational spectroscopy. Chemical analysis shows the mineral contains P, Mg with very minor Fe. Thus, the formula of the studied ushkovite is Mg32+(PO4)2·8H2O. The Raman spectrum shows an intense band at 953 cm−1 assigned to the ν1 symmetric stretching mode. In the infrared spectra complexity exists with multiple antisymmetric stretching vibrations observed, due to the reduced tetrahedral symmetry. This loss of degeneracy is also reflected in the bending modes. Strong infrared bands around 827 cm−1 are attributed to water librational modes. The Raman spectra of the hydroxyl-stretching region are complex with overlapping broad bands. Hydroxyl stretching vibrations are identified at 2881, 2998, 3107, 3203, 3284 and 3457 cm−1. The wavenumber band at 3457 cm−1 is attributed to the presence of FeOH groups. This complexity is reflected in the water HOH bending modes where a strong infrared band centered around 1653 cm−1 is found. Such a band reflects the strong hydrogen bonding of the water molecules to the phosphate anions in adjacent layers. Spectra show three distinct OH bending bands from strongly hydrogen-bonded, weakly hydrogen bonded water and non-hydrogen bonded water. Vibrational spectroscopy enhances our knowledge of the molecular structure of ushkovite.

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ID Code: 83747
Item Type: Journal Article
Refereed: Yes
Keywords: Ushkovite, Phosphate, Hydroxyl, raman spectroscopy, SEM, EDX
DOI: 10.1016/j.molstruc.2014.10.017
ISSN: 1872-8014
Divisions: Current > Schools > School of Chemistry, Physics & Mechanical Engineering
Current > QUT Faculties and Divisions > Science & Engineering Faculty
Copyright Owner: Copyright 2015 Elsevier
Copyright Statement: Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
Deposited On: 26 Apr 2015 23:15
Last Modified: 02 Nov 2015 18:10

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