Structural characterization of tellurite glasses doped with transition metal oxides using Raman spectra and ab initio calculations

Systems of iron tellurite glasses were prepared by meltquenching with compositions of [85%TeO2 + 5%Fe2O3 + 10%TMO], where transition metal oxides (TMO) are TiO2, V2O5, MnO, CoO, NiO and CuO. Furthermore, the main structural units of these samples have been characterized by means of Raman spectra (150-1200 cm(-1)) as well as wavenumber predictions by means of Gaussian 98 ab initio calculations for the proposed site symmetries of TeO44- triagonal bipyramid (C-2v) and Te2O76- bridged tetrahedra (C-s and C-1). Aided by normal coordinate analysis, calculated vibrational frequencies, Raman scattering activities, force constants in internal coordinates and potential energy distributions (PEDs), revised vibrational assignments for the fundamental modes have been proposed. The main structural features are correlated to the dominant units of triagonal bipyramid (tbp) or bridged tetrahedral (TeO3+1 binds to TeO3 through TeOTe bridge; corner sharing). Moreover, the Raman spectra of the investigated tellurites reflect a structural change from tbp (coordination number is four) to triagonal pyramidal (coordination number is three). (c) 2005 Elsevier B.V. All rights reserved.