Boson peak, heterogeneity and intermediate-range order in binary SiO₂-Al₂O₃ glasses

Area of Science:

• Materials Science
• Solid State Chemistry
• Glass Science

Background:

• Structural heterogeneity in aluminosilicate glasses impacts optical fiber performance and dopant behavior.
• Understanding molecular-scale structure is key to controlling material properties.

Purpose of the Study:

• To assess structural heterogeneity in aluminosilicate glasses using low-frequency vibrational modes.
• To correlate molecular-scale structure with alumina content.

Main Methods:

• Low-temperature heat capacity measurements to determine vibrational density of states (VDoS).
• Low-frequency Raman spectroscopy to obtain the Raman coupling coefficient.
• Extraction of the average dynamic correlation length as a function of alumina content.

Main Results:

• The average dynamic correlation length decreases from 3.9 nm to 3.3 nm with increasing alumina content (0–7 mol%).
• Mild alumina doping leads to a slight increase in average inter-particle distance.
• Evidence of oxygen tricluster species formation was observed.

Conclusions:

• Mild alumina doping enhances structural homogeneity at the molecular scale in aluminosilicate glasses.
• Findings align with Loewensteinian dynamics, providing insights into glass structure modification.