RAMAN-SPECTROSCOPIC INVESTIGATIONS OF THE EFFECT OF THE DOPING METAL ON THE STRUCTURE OF BINARY TELLURIUM-OXIDE GLASSES

Raman studies over the range 10 to 1000 cm(-1) have been performed on binary tellurium-oxide glasses (1 - x)TeO2-xMO (M = Pb, Zn or Mg) prep ared using a conventional melt technique. The intensities and position s of Raman bands observed in the range above 250 cm(-1) were found to depend both on the compound oxide and on the amount of doping. indeed, the ratio of the intensity of the band around 680 cm(-1) (assigned to vibrations of TeO4 trigonal bipyramids) with respect to that of the c omponent around 750 cm(-1) (related to stretching-vibrations in TeO3+1 , TeO3 and MO groups) are affected in different ways for the glass-mod ifier MgO and for the intermediate glass-formers PbO and ZnO. Concurre ntly, an explicit dependence on the compound oxide and amount of dopin g was also observed on the maximum of the boson peak (BP) in the low-f requency region around 40 cm(-1). The structural correlation lengths i n the glasses, calculated using the model described by Shuker and Gamm on, were found to be about 0.50 nm for (1 - x)TeO2-xMgO glasses and ar ound 0.65 nm for (1 - x)TeO2-xMO (M = Pb or Zn) glasses. All these res ults are interpreted in terms of the effect of the metal oxide on the changes induced in the structural arrangements of (1)(infinity)[TeO4-T eO3] chains. (C) 1997 Elsevier Science B.V.