A-thermal elastic behavior of silicate glasses

Abstract

Depending on the composition of silicate glasses, their elastic moduli can increase or decrease as function of the temperature. Studying the Brillouin frequency shift of these glasses versus temperature allows the a-thermal composition corresponding to an intermediate glass to be determined. In an intermediate glass, the elastic moduli are independent of the temperature over a large temperature range. For sodium alumino-silicate glasses, the a-thermal composition is close to the albite glass (NaAlSi3O8). The structural origin of this property is studied by in situ high temperature Raman scattering. The structure of the intermediate albite glass and of silica are compared at different temperatures between room temperature and 600 °C. When the temperature increases, it is shown that the high frequency shift of the main band at 440 cm(-1) in silica is a consequence of the cristobalite-like alpha-beta transformation of 6-membered rings. This effect is stronger in silica than bond elongation (anharmonic effects). As a consequence, the elastic moduli of silica increase as the temperature increases. In the albite glass, the substitution of 25% of Si(4+) ions by Al(3+) and Na(+) ions decreases the proportion of SiO2 6-membered rings responsible for the silica anomaly. The effects of the silica anomaly balance the anharmonicity in albite glass and give rise to an intermediate a-thermal glass. Different networks, formers or modifiers, can be added to produce different a-thermal glasses with useful mechanical or chemical properties.

Understanding Sodium Borate Glasses and Melts from Their Elastic Response to Temperature

“…). Such glasses with nearly temperature‐independent elastic moduli are called intermediate glasses, which have attracted much attention in recent literature with a potential to develop athermal Brillouin fibers for sensor applications …”

Understanding the structural origin of intermediate glasses

“…Brillouin longitudinal frequency shift of albite glass, a glass derived from the naturally occurring sodium feldspar, was found to remain constant with temperature . Although albite is an extensively studied glass in the geology community, all of its elastic constants at high temperature have not been reported to our best knowledge . By using in situ high‐temperature Brillouin light scattering (BLS) technique in this study, we found that all of the elastic moduli of albite glass remain constant up to its glass transition temperature ( T g ) and above.…”

“…Mechanically modified silica glass by a systematic pressure quenching was found to exhibit intermediate behavior without chemical modification . Brillouin longitudinal frequency shift of albite glass, a glass derived from the naturally occurring sodium feldspar, was found to remain constant with temperature . Although albite is an extensively studied glass in the geology community, all of its elastic constants at high temperature have not been reported to our best knowledge .…”

“…It is natural to imagine that in between there exist intermediate glasses with elastic responses independent of temperature and/or pressure. Such glasses have attracted much attention in recent literature with a great potential for developing a‐thermal optical fibers for enhanced telecommunication, sensors, and high‐energy laser systems . These glasses would also prove useful in applications where a broad range of thermal and mechanical stimulation is expected …”

Tailoring structure and properties of silica glass aided by computer simulation

“…In between, intermediate glass with temperature or pressure independent elastic moduli can be obtained. [6][7][8][9] In this study, by either pressurequenching, helium-stuffing, or alkali-modifying silica glass, we can change its elastic response to pressure systematically, i.e., to have a negative, zero, and positive slope. Then, by scrutinizing the structural differences among these three types of glasses in molecular dynamics (MD) simulations, we uncovered the structural origin of the elastic anomaly in silica glass, which can be attributed to localized structural transitions, analogous to those that occur in its crystalline counterparts.…”