Effects of Composition, Pressure, and Temperature on the Elastic Properties of SiO2-TiO2 Glasses: An Integrated Ultrasonic and Brillouin Study

We have systematically investigated the elastic properties (p, V-p, V-S, K, mu and sigma) of eight SiO2-TiO2 glasses, varying in composition from 1.3 to 14.7 wt% TiO2, as a function of pressure up to 0.5 GPa by the pulse superposition (PSP) ultrasonic technique, and two compositions (1.3 and 9.4 wt% Ti0 2 ) up to similar to 5.7 GPa by Brillouin scattering in a diamond anvil cell. The parameters were also measured after annealing to 1020 degrees C. Composition-elasticity relationships, except for K and sigma, are more or less linear; the annealing simply makes the relationships more uniform (less scatter). There is excellent agreement between the ultrasonic and Brillouin measurements at ambient and high pressure. The pressure-induced anomalous elastic behavior (negative dV(P)/dP and dK/dP) becomes more negative (more compressible) with the increasing TiO2 content. Correspondingly, the acoustic GrUneisen parameters become more negative with increases in the TiO2 content, reaching a minimum near similar to 8-10 wt% TiO2. The comparison of the low- and high-pressure ultrasonic and Brillouin V-P and Vs in two glasses (1.3 and 9.4 wt% TiO2) shows excellent agreement, defining the reversible elastic behavior at low pressures and irreversible behavior at higher pressures (>= 5.7 GPa) well. This result is consistent with our previous high-pressure Raman study showing an irreversible structural change in a similar pressure range.