Thermal and Mechanical Properties of Lithium Borate Glasses in Relation to the Glass Structure

Abstract

In lithium borate glasses RLi2O⋅B2O3 (0≤R<0.4), the following experimental results were obtained: 1. The density increases monotonically with increasing R. 2. Both velocities of longitudinal and transverse ultrasonic waves increase monotonically with increasing R. 3. The elastic constants such as bulk modulus and Young's modulus increase monotonically with increasing R. 4. The linear expansion coefficient shows a broad minimum at around R=0.25. 5. The Poisson ratio shows a minimum at around R=0.10 and a maximum at around R=0.20. 6. Each of the temperature coefficients of velocities for longitudinal and transverse ultrasonic waves shows a sharp minimum at R=0.10 and a sharp change in slope at R=0.20. The experimental results 1, 2 and 3 can be ascribed to a change in short-range order groups. The experimental result 4 is ascribable to the most compact configuration at around R=0.25. The experimental results 5 and 6 are ascribable to a change in crosslink between six-membered borate rings.