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

• Main Authors: Murli H. Manghnani, Quentin Williams, Teruyuki Matsui, Peter C. Schultz, Charles R. Kurkjian
• Format: Article
• Language: English
• Published: MDPI AG 2020-05-01
• Series: Minerals
• Subjects: SiO₂–TiO₂ glasses; elastic properties; pressure-temperature dependences; ultrasonic method; Brillouin scattering; equation of state
• Online Access: https://www.mdpi.com/2075-163X/10/5/481

We have systematically investigated the elastic properties (<i>ρ</i>, <i>V</i>_P, <i>V</i>_S, <i>K</i>, and <i>σ</i>) 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% TiO₂) up to ~5.7 GPa by Brillouin scattering in a diamond anvil cell. The parameters were also measured after annealing to 1020 °C. Composition–elasticity relationships, except for <i>K</i> and <i>σ</i>, 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 d<i>V</i>_P/d<i>P</i> and d<i>K</i>/d<i>P</i>) becomes more negative (more compressible) with the increasing TiO₂ content. Correspondingly, the acoustic Grüneisen parameters become more negative with increases in the TiO₂ content, reaching a minimum near ~8–10 wt% TiO_2. The comparison of the low- and high-pressure ultrasonic and Brillouin V_P and V_S 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.