Thermo-Raman spectroscopic study of the uranium mineral sabugalite

The changes in the structure of sabugalite were investigated using thermo-Raman and infrared spectroscopy based on the results of thermogravimetric analysis. Two Raman bands are observed at 835 and 830 cm(-1) assigned to the (UO2)(2+) stretching vibrations resulting from the non-equivalence of the uranyl bonds (UO2)(2+). These bands give calculated U-O bond lengths of 1.773 and 1.780 angstrom. A low-intensity band is observed at 895 cm(-1) assigned to the nu(3) antisymmetric stretching vibration of (UO2)(2+) units. Five bands are observed in the 950-1050 cm(-1) region in the Raman spectrum of sabugalite and are assigned to the nu(3) antisymmetric stretching vibration of (PO4)(3-) units. Changes in the Raman spectra reflect changes in the structure of sabugalite as dehydration occurs. No (PO4)(3-) symmetric stretching mode is observed. This result is attributed to the non-equivalence of the PO bonds in the PO4 units. The PO4 vibrations were not affected by dehydration. Thermo-Raman spectroscopy proved to be a very powerful technique for the study of the changes in the structure of sabugalite during dehydration. Copyright (c) 2005 John Wiley & Sons, Ltd.