Abstract
The structure and stability of ternary tellurite (50 – x ) V~2~O~5~–x PbO–50TeO~2~ glasses have been investigated by means of ultrasonic studies. Ultrasonic velocities and attenuation measurements have been made over a wide range of temperatures from 150 to 480 K at 5 MHz. At room temperature, a gradual increase in density and a decrease in velocities and Debye temperature with increase in PbO content have been observed. A change in the trend of variation in T ~g~, elastic moduli and attenuation with an increase in PbO content has been noticed at 20 wt% of PbO. These results reveal a change in the Te co‐ordination from trigonal bipyramid to trigonal pyramid, with the formation of ionic bonds due to the addition of PbO. In addition, the breaking of more Te–O–Te and Te–O–Pb linkages, leaving non‐bridging oxygen with increasing in PbO content, is known to occur in these glasses. The temperature dependence of the parameters investigated has been explained in terms of the weakening of the structure, which is due to the instability of the TeO~4~ trigonal bipyramid unit with increasing temperature. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)