Raman scattering, differential scanning calorimetry and Nd3+ spectroscopy in alkali niobium tellurite glasses

Alkali niobium tellurite glasses have been prepared and some of their prope rties measured by differential scanning calorimetry and Raman scattering. T he vitreous domain was established in the pseudo ternary phases diagram for the system TeO2-Nb2O5-(0.5K(2)O-0.5Li(2)O). Raman scattering shows that fo r samples in the TeO2 rich part of the phase diagram the vitreous structure is composed essentially of (TeO4) units connected by the vertices, as in t he alpha-TeO2 crystal. The addition of alkali and niobium oxides causes dep olymerization to occur with structures composed essentially of (TeO3) and ( NbO6) units. Samples with the composition (mol%) 80TeO(2)-10Nb(2)O(5)-5K(2) O-5Li(2)O, stable against crystallization, were prepared containing up to 1 0% mol Nd3+. The addition of this oxide increases the rigidity of the vitre ous network shifting characteristic temperatures to higher temperatures. Fo r the 10% Nd3+ sample amorphous phase separation is assumed to exist from t he observation of two glass transition temperatures. Spectroscopic properti es such as Judd-Ofelt Omega(lambda) intensity parameters, radiative emissio n probabilities, and induced emission cross sections were calculated. From these results and also from the emission quenching observed as a function o f Nd3+ concentration, we suggest that these glasses could be utilized in op tical amplifying devices. (C) 1999 Elsevier Science B.V. All rights reserve d.