Optical and spectroscopic characterization of permanently densified GeO₂glasses

Abstract

Optical and spectroscopic characterization was carried out on densified vitreous germania glasses retrieved from pressures in the range 2-6 GPa. The density of the obtained glasses increased with applied pressure. Ultrasonic and Brillouin measurements revealed an increase of the longitudinal and shear sound velocity, in agreement with the hardening of the elastic medium. Raman measurements allowed the structural modification of the system to be studied as a function of its density and showed the evolution of the boson peak, which shifts towards higher frequencies and decreases in intensity.

Structural changes and elastic characteristics of permanently densified vitreousB2O3

“…This is because the tetracoordinated boron atoms represent a unique source for the connectivity (defined as the number of bridging bonds per NFI) and the associated stiffening of the borate network. The variations in ω BP and sound velocities vs quenching pressure in hot densified glassy B 2 O 3 are considerably larger than those revealed in glasses compacted at temperatures below T g , 31,32 Fig. 4.…”

Effects of permanent densification on the vibrational density of states of vitreous silica

“…The starting block was drilled in cylindrical pieces of 4 mm diameter and 4 mm length, which were densified using a high-temperature high-pressure multi-anvil apparatus [27]. The samples were compressed at pressures of 2, 4, 6 and 8 GPa, then heated at T = 500 ∘ C for 10 min with a heating rate of 50°C/min.…”

The Raman coupling function in permanently densified GeO2glasses

“…where the high frequency bands are not significantly perturbed by the densification process. In order to study the effects of the densification process from the molecular point of view, high frequency Raman scattering was performed on all the available samples [17]. No strong structural modification has been detected with the densification process.…”

“…The obtained glass block was cut into cylindrical pieces which were densified using an HT-HP multi-anvil apparatus following a procedure described elsewhere [17]. The samples were compressed at 2, 4 and 6 GPa and then heated at 673 K for 2 minutes under pressure.…”