Raman spectroscopic study of Nd-doped 10Na2O–90TeO2 glasses

Over the Nd2O3 concentration region from 0.1 to 2.5 mol%, our Raman spectroscopic study showed that adding Nd to a base 10Na2O–90TeO2 tellurite glass converts TeO4 trigonal bipyramid (tbp) units to TeO3 trigonal pyramid (tp) units and possibly some terminal TeO3+1 polyhedra. The Nd effect on the speciation of tellurite structural groups is similar to that of other monovalent (such as alkalis), divalent (such as Zn), and trivalent (such as La) metal cations. The previously observed Nd–O local structural transition was 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 represents the stretching vibration mode of TeO4 tbp units and the latter represents 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) linkages. Our study showed a significant decrease in the E-band intensity of the glass with 2.5 mol% Nd2O3. It follows that a considerable structure disruption of the tellurite network takes place when the Nd cation is close to its solubility limit.