A vibrational spectroscopic study of the phosphate mineral cyrilovite Na(Fe³⁺)₃(PO₄)₂(OH)₄¡¤2(H₂O) and in comparison with wardite

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• 作者：Ray L. Frost^a ; ^{r.frost@qut.edu.au} ; Yunfei Xi^a ; Ricardo Scholz^b
• 关键词：Cyrilovite ; Wardite ; Phosphate ; Hydroxyl ; Raman spectroscopy ; Infrared
• 刊名：Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
• 出版年：2013
• 出版时间：May, 2013
• 年：2013
• 卷：108
• 期：Complete
• 页码：244-250
• 全文大小：786 K

文摘

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 Fe³⁺ 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 ¦Í₁ symmetric stretching vibrations. A series of low intensity bands at 1105, 1136, 1177 and 1184 cm^?1 are assigned to the ¦Í₃ 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 ¦Í₁ symmetric stretching mode. Raman bands are observed at 612 and 631 cm^?1 and are assigned to the ¦Í₄ out of plane bending modes of the 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.