Raman spectroscopic study of Nd-doped 10Na(2)O-90TeO(2) glasses

Over the Nd2O3 concentration region from 0.1 to 2.5 mol%, our Raman spectro scopic study showed that adding Nd to a base 10Na(2)O-90TeO(2), tellurite g lass converts TeO4 trigonal bipyramid (tbp) units to TeO3 trigonal pyramid (tp) units and possibly some terminal TeO3+1 polyhedra. The Nd effect on th e speciation of tellurite structural groups is similar to that of other mon ovalent (such as alkalis), divalent (such as Zn), and trivalent (such as La ) metal cations. The previously observed Nd-O local structural transition w as also found in the current study. Namely. a transition near 1 mol% Nd2O3 was observed in the correlations, both band position and intensity, between two Raman stretching vibration bands near 600 and 730 cm (1). The former r epresents the stretching vibration mode of TeO4 tbp units and the latter re presents the stretching vibration mode of TeO3 tp units. A Raman band, near 465 cm(-1), represents a bending vibration mode of Te-O-Te (or O-Te-O) lin kages. Our study showed a significant decrease in the E-band intensity of t he glass with 2.5 mol% Nd2O3. It follows that a considerable structure disr uption of the tellurite network takes place when the Nd cation is close to its solubility limit. (C) 2001 Elsevier Science B.V. All rights reserved.