Permanently densified SiO2 glasses: a structural approach.

Area of Science:

• Materials Science
• Solid State Chemistry
• Glass Science

Background:

• Silica glass densification is achieved through various pressure and temperature paths.
• Density is the primary macroscopic parameter for characterizing compressed silica.
• Understanding structural modifications is crucial for tailoring silica glass properties.

Purpose of the Study:

• To compare structural modifications in silica glass densified via different routes.
• To investigate the influence of temperature and stress conditions on silica glass structure.
• To correlate microstructural changes with macroscopic density.

Main Methods:

• Preparation of densified silica glasses using cold and high-temperature (up to 1020 °C) compressions.
• Characterization of densified silica glasses using micro-Raman spectroscopy.
• Analysis of intertetrahedral angles and ring populations (3-membered rings).

Main Results:

• Intertetrahedral angles decrease with compression; higher values observed in high-temperature compressed samples compared to cold-compressed ones.
• The proportion of 3-membered rings increases with density in cold compression.
• Elevated temperatures during compression reduce the population of 3-membered rings and result in more relaxed structures with lower internal stresses.

Conclusions:

• Temperature significantly influences structural reorganization during silica glass densification.
• High-temperature compression yields a more relaxed silica glass structure with reduced internal stresses compared to cold compression.
• The study provides insights into the role of stress conditions (hydrostatic vs. non-hydrostatic) on glass structure and estimates average intertetrahedral angles and their distributions.