title: A vibrational spectroscopic study of the phosphate mineral cyrilovite Na(Fe3+)3(PO4)2(OH)4·2(H2O) and in comparison with wardite.
abstract: Vibrational spectroscopy enables subtle details of the molecular structure of cyrilovite to be determined. Single crystals of a pure phase from a Brazilian pegmatite were used. Cyrilovite is the Fe(3+) member of the wardite group. The infrared and Raman spectroscopy were applied to compare the structure of cyrilovite with that of wardite. The Raman spectrum of cyrilovite in the 800-1400 cm(-1) spectral range shows two intense bands at 992 and 1055 cm(-1) assigned to the ν1PO4(3-) symmetric stretching vibrations. A series of low intensity bands at 1105, 1136, 1177 and 1184 cm(-1) are assigned to the ν3PO4(3-) antisymmetric stretching modes. The infrared spectrum of cyrilovite in the 500-1300 cm(-1) shows much greater complexity than the Raman spectrum. Strong infrared bands are found at 970 and 1007 cm(-1) and are attributed to the ν1PO4(3-) symmetric stretching mode. Raman bands are observed at 612 and 631 cm(-1) and are assigned to the ν4 out of plane bending modes of the PO4(3-) unit. In the 2600-3800 cm(-1) spectral range, intense Raman bands for cyrilovite are found at 3328 and 3452 cm(-1) with a broad shoulder at 3194 cm(-1) and are assigned to OH stretching vibrations. Sharp infrared bands are observed at 3485 and 3538 cm(-1). Raman spectroscopy complimented with infrared spectroscopy has enabled the structure of cyrilovite to be ascertained and compared with that of wardite.
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia. r.frost@qut.edu.au
authors.forename: Ray L
authors.initials: RL
authors.lastname: Frost
authors.forename: Yunfei
authors.initials: Y
authors.lastname: Xi
authors.forename: Ricardo
authors.initials: R
authors.lastname: Scholz
mesh_terms: D017607:Aluminum Compounds / Q000737:chemistry*; D003460:Crystallization; D005290:Ferric Compounds / Q000737:chemistry*; D008903:Minerals / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry*; D013052:Spectrometry, X-Ray Emission; D013055:Spectrophotometry, Infrared; D013059:Spectrum Analysis, Raman; D014732:Vibration
chemical_list: D017607:Aluminum Compounds; D005290:Ferric Compounds; D008903:Minerals; D010710:Phosphates