Revealing the relationship between liquid fragility and medium-range order in silicate glasses

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid State Chemistry

Background:

• The glass transition, a critical phenomenon in materials science, remains poorly understood.
• Fragility quantifies the sharpness of dynamical arrest during the glass transition, but its structural origins are debated.

Purpose of the Study:

• To investigate the relationship between medium-range order and glass fragility.
• To identify a measurable structural parameter that governs glass transition dynamics.

Main Methods:

• Analysis of neutron-diffraction data from aluminosilicate glasses.
• In-situ high-temperature neutron-scattering experiments.
• Correlation analysis between structural parameters and fragility.

Main Results:

• A strong inverse correlation was found between average medium-range distance (MRD) and fragility.
• Glasses with low MRD values exhibit an excess of small, unstable network rings.
• These unstable rings deform readily with temperature, increasing fragility.

Conclusions:

• Medium-range order, specifically MRD, is a key determinant of glass transition fragility.
• The stability of network rings within the glass structure dictates the sharpness of dynamical arrest.
• This finding provides a new structural perspective on the glass transition phenomenon.