Raman spectroscopy study of pressure-induced structural changes in sodium borate glass

• We study pressure-induced structural changes in a sodium borate glass using Raman spectroscopy.
• Perform both cold compression (up to 9 GPa at RT) and hot compression (up to 1 GPa at Tg)
• Decrease in fraction of boroxol rings and increase in fraction of non-ring structures with pressure
• Same changes occur elastically during cold compression and inelastically upon hot compression.

Pressure-induced structural changes in a sodium borate glass have been studied up to ~ 9 GPa by in situ micro-Raman spectroscopy in a diamond anvil cell at ambient temperature. The results show a decrease in the fraction of boroxol rings and an increase in the fraction of non-ring structures with increasing pressure. These findings are compared with Raman spectra of the same glass composition compressed at 1 GPa at its glass transition temperature (406 °C). We show similarities in the medium-range structural changes of the borate glass compressed at high-pressure/low-temperature (9 GPa, 25 °C) and intermediate-pressure/high-temperature (1 GPa, ~ 400 °C) conditions. The structural changes are elastic during cold compression but inelastic as a result of the hot compression. We discuss this difference in relation to densification and Raman inactive structural changes.