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

Abstract

Glasses Al2/3O–TeO2, ZnO–TeO2 and R2/3O–ZnO–TeO2 (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 (T g), density (ρ), and ultrasonic longitudinal (V L) and transverse (V T) velocities. In addition, atomic packing density (C g), elastic moduli, and Poisson’s ratio (σ) were evaluated from the measured properties. It was found that Al2/3O leads to cross-linked alumino-tellurite networks by strong Te–O–Al bonds, which cause a profound enhancement in T g. The influence of ZnO and B2/3O on T g is relatively smaller due to the weaker cross-linking effects of ZnO4 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 V T and mostly on the V L 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 Al2/3O content in the binary and ternary glasses studied here, but increasing trends with ZnO and B2/3O additions in glasses ZnO–TeO2 and B2/3O–ZnO–TeO2, 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 C g correlation established previously for a range of glasses not including tellurites so far. Finally, the sound velocities and Poisson’s ratio of pure TeO2 glass were determined for the first time and found to differ markedly from those in the literature for TeO2 glass melted in alumina crucible; this is because the latter glass is highly doped by Al2O3 leached from the alumina crucible.

Short-range structure, the role of bismuth and property–structure correlations in bismuth borate glasses

“…For radii we use effective ionic radii of Shannon, 88 taking the values r O = 1.35 Å for oxygen and r Bi = 1.03 Å for bismuth, the latter corresponding to Bi in six-fold coordination. For the ionic radius of boron we take into consideration the change in coordination number with composition (x) and write r B = X 4 r B(4) + (1 À X 4 )r B(3) , 89 where the boron ionic radii for 4-and 3-fold coordination are r B(4) = 0.11 Å and r B(3) = 0.01 Å; 88 recognizing though that boron has a very small effect on C g in comparison to oxygen and bismuth. The calculated C g values are given in Table 3, while the evolution of the atomic packing density with composition is demonstrated in Fig.…”

Features of electronic polarizability and approach to unique properties in tellurite glasses

“…They demonstrated that tellurite glasses are fragile even from the viewpoint of mechanical properties because of their weak bond strengths and open atomic packing structures . Tagiara et al showed recently that the mechanical properties of ZnO‐TeO 2 glasses could be improved by introducing B 2 O 3 (eg, x B 2 O 3 ‐(30 − x )ZnO‐70TeO 2 , 0 ≦ x ≦ 30) that leads to increased bonding strength and to larger packing density of the glass network. The combination of B 2 O 3 (the acidic oxide and low electronic polarizability) and TeO 2 (the basic oxide and high electronic polarizability) is a good design for improving poor mechanical properties of TeO 2 ‐based glasses.…”

Niobate in silicate and phosphate glasses: Effect of glass basicity on crucible dissolution

“…Especially in the field of oxide glasses, the thermodynamic model of Shakhmatkin and Vedishcheva has been successfully applied in previous years. [1][2][3][4][5][6][7][8][9] The SVTDM model considers glasses and melts to be an ideal solution formed by salt products of equilibrium chemical reactions of simple starting substances, e.g. oxides, halides, etc.…”

“…In recent years, the effect of the crucible material on glass composition, structure and, subsequently, the glass thermal, electrical and mechanical properties has attracted increasing attention in glass chemistry and physics [1][2][3][4][5][6][7]. Especially, the dissolution of alumina crucibles was shown to modify phosphate, silicate or tellurite networks through addition of Al 2 O 3 leached from the crucible.…”

“…Especially, the dissolution of alumina crucibles was shown to modify phosphate, silicate or tellurite networks through addition of Al 2 O 3 leached from the crucible. Differences in the glass transition temperature T g by as much as 100 o C have been observed, while the glass network is substantially altered and, especially for tellurium dioxide, glass formation is significantly enhanced [1,5]. Melting phosphate glasses in silica crucibles is also known to dissolve silicate species into the glass, though dissolution seems to be less when compared to alumina crucibles [8].…”