A vibrational spectroscopic study of the phosphate mineral minyulite KAl2(OH,F)(PO4)2⋅4(H2O) and in comparison with wardite

Frost, Ray L., López, Andrés, Xi, Yunfei, Cardoso, Luiz Henrique, & Scholz, Ricardo (2014) A vibrational spectroscopic study of the phosphate mineral minyulite KAl2(OH,F)(PO4)2⋅4(H2O) and in comparison with wardite. Spectrochimica Acta Part A : Molecular and Biomolecular Spectroscopy, 124, pp. 34-39.

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Abstract

Vibrational spectroscopy enables subtle details of the molecular structure of minyulite KAl2(OH,F)(PO4)2⋅4(H2O). Single crystals of a pure phase from a Brazilian pegmatite were used. Minyulite belongs to the orthorhombic crystal system. This indicates that it has three axes of unequal length, yet all are perpendicular to each other. The infrared and Raman spectroscopy were applied to compare the structure of minyulite with wardite. The reason for the comparison is that both are Al containing phosphate minerals.

The Raman spectrum of minyulite shows an intense band at 1012 cm−1 assigned to the ν1PO43- symmetric stretching vibrations. A series of low intensity Raman bands at 1047, 1077, 1091 and 1105 cm−1 are assigned to the ν3PO43- antisymmetric stretching modes. The Raman bands at 1136, 1155, 1176 and 1190 cm−1 are assigned to AlOH deformation modes. The infrared band at 1014 cm−1 is ascribed to the PO43- ν1 symmetric stretching vibrational mode. The infrared bands at 1049, 1071, 1091 and 1123 cm−1 are attributed to the PO43- ν3 antisymmetric stretching vibrations. The infrared bands at 1123, 1146 and 1157 cm−1 are attributed to AlOH deformation modes. Raman bands at 575, 592, 606 and 628 cm−1 are assigned to the ν4 out of plane bending modes of the PO43- unit. In the 2600–3800 cm−1 spectral range, Raman bands for minyulite are found at 3661, 3669 and 3692 cm−1 are assigned to AlOH/AlF stretching vibrations. Broad infrared bands are also found at 2904, 3105, 3307, 3453 and 3523 cm−1. Raman bands at 3225, 3324 cm−1 are assigned to water stretching vibrations. A comparison is made with the vibrational spectra of wardite. Raman spectroscopy complimented with infrared spectroscopy has enabled aspects of the structure of minyulite to be ascertained and compared with that of other phosphate minerals.

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ID Code: 66530
Item Type: Journal Article
Refereed: Yes
Keywords: Minyulite, Wardite, Phosphate, Hydroxyl, Raman spectroscopy, Infrared
DOI: 10.1016/j.saa.2013.12.039
ISSN: 13861425
Subjects: Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000) > PHYSICAL CHEMISTRY (INCL. STRUCTURAL) (030600) > Structural Chemistry and Spectroscopy (030606)
Divisions: Current > Schools > School of Chemistry, Physics & Mechanical Engineering
Current > QUT Faculties and Divisions > Science & Engineering Faculty
Copyright Owner: Copyright 2013 Elsevier B.V.
Copyright Statement: NOTICE: this is the author’s version of a work that was accepted for publication in Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, [Volume 124, 24 (April 2014)] DOI: 10.1016/j.saa.2013.12.039
Deposited On: 22 Jan 2014 23:13
Last Modified: 28 Apr 2016 12:15

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