A vibrational spectroscopic study of the phosphate mineral Wardite NaAl₃(PO₄)₂(OH)₄路2(H₂O)

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• 作者：Ray L. Frost ; ^{r.frost@qut.edu.au} ; Yunfei Xi
• 关键词：Wardite ; Cyrilovite ; Phosphate ; Hydroxyl ; Raman spectroscopy
• 刊名：Spectrochimica Acta Part A ; Molecular and Biomolecular Spectroscopy
• 出版年：2012
• 期刊代码：99_13861425
• 类别：ch
• 出版时间：July, 2012
• 卷：93
• 期：Complete
• 页码：155-163
• 文件大小：1177 K

摘要

Three wardite mineral samples from different origins have been analysed by vibrational spectroscopy. The mineral is unusual in that it belongs to a unique symmetry class, namely the tetragonal-trapezohedral group. The structure of wardite contains layers of corner-linked OH bridged MO₆ octahedra stacked along the tetragonal C-axis in a four-layer sequence and linked by PO₄ groups. Consequentially not all phosphate units are identical. Thus, two intense Raman bands observed at 995 and 1051 cm^鈭? are assigned to the 谓₁ PO₄^{3鈭?/sup> symmetric stretching mode. Intense Raman bands are observed at 605 and 618 cm鈭? with shoulders at 578 and 589 cm鈭? are assigned to the 谓₄ out of plane bending modes of the PO₄3鈭?/sup>. The observation of multiple bands supports the concept of non-equivalent phosphate units in the structure. Sharp infrared bands are observed at 3544 and 3611 cm鈭? are attributed to the OH stretching vibrations of the hydroxyl units. Vibrational spectroscopy enables subtle details of the molecular structure of wardite to be determined.}