Short-Range Structure, Thermal and Elastic Properties of Binary and Ternary Tellurite Glasses.

Glasses AlO-TeO, ZnO-TeO and RO-ZnO-TeO (R = Al, B) were prepared by melting in Pt crucibles and studied for correlations between structure and thermal as well as mechanical properties, whereby the glass composition is varied to tailor the short-range speciation of tellurite, aluminate, and borate groups. The glass structure was studied by Raman and infrared spectroscopy analyses, and the measured properties include glass-transition temperature (), density (ρ), and ultrasonic longitudinal () and transverse () velocities. In addition, atomic packing density (), elastic moduli, and Poisson's ratio (σ) were evaluated from the measured properties. It was found that AlO leads to cross-linked alumino-tellurite networks by strong Te-O-Al bonds, which cause a profound enhancement in . The influence of ZnO and BO on is relatively smaller due to the weaker cross-linking effects of ZnO tetrahedra and of Te···O-B bonds. Short-range bonding characteristics, interatomic bonding energy differences, and atomic packing density were found to have a strong effect on and mostly on the sound velocity. The combined effects of structure and bonding are nicely expressed in the composition dependence of Poisson's ratio; it exhibits decreasing trends with AlO content in the binary and ternary glasses studied here, but increasing trends with ZnO and BO additions in glasses ZnO-TeO and BO-ZnO-TeO, respectively. The results for Poisson's ratio and atomic packing density for the studied glasses were found to fit nicely in the global σ versus correlation established previously for a range of glasses not including tellurites so far. Finally, the sound velocities and Poisson's ratio of pure TeO glass were determined for the first time and found to differ markedly from those in the literature for TeO glass melted in alumina crucible; this is because the latter glass is highly doped by AlO leached from the alumina crucible.