Raman spectroscopic study of the tellurite minerals: Rajite and denningite

Tellurites maybe subdivided according to formula and structure. There are five groups based upon the formulae(a)A(XO3), (b) A(XO3)center dot xH(2)O,(c)A(2)(XO3)(3)center dot xH(2)O, (d)A(2)(X2O5) and (e)A(X3O8). Raman spectroscopy has been used to study rajite and denningite, examples of group (d). Minerals of the tellurite group are porous zeolite-like materials. Raman bands for rajite observed at 740, and 676 and 667cm(-1) are attributed to the nu 1 (Te2O5)(2-) symmetric stretching mode and the nu(3) (TeO3)(2-) antisymmetric stretching modes, respectively. A second rajite mineral sample provided a more complex Raman spectrum with Raman bands at 754 and 731 cm(-1) assigned to the nu(1), (Te2O5)(2-) symmetric stretching modes and two bands at 652 and 603 cm(-1) are accounted for by the nu(3) (Te2O5)(2-) antisymmetric stretching mode. The Raman spectrum of dennigite displays an intense band at 734cm(-1) attributed to the nu(1) (Te2O5)(2-) symmetric stretching mode with a second Raman band at 674 cm(-1) assigned to the nu(3) (Te2O5)(2-) antisymmetric stretching mode. Raman bands for rajite, observed at (346, 370) and 438 cm(-1) are assigned to the (Te2O5)(2-) nu(2) (A(1)) bending mode and nu(4) (E) bending modes. (C) 2008 Elsevier B.V. All rights reserved.