Relaxation dynamics of glasses along a wide stability and temperature range

TL;DR

This study uses ultrafast calorimetry to explore glass relaxation dynamics at high temperatures, revealing super-Arrhenius behavior and a unified description linking liquid and glass states across different materials.

Contribution

It introduces a novel high-temperature measurement approach and demonstrates a common VFT-like description for diverse glassy materials, bridging liquid and glass dynamics.

Findings

Relaxation times follow super-Arrhenius behavior above devitrification temperature.

A unified VFT-like expression describes both liquid and glass states.

Indomethacin glasses obey density scaling laws similar to liquids.

Abstract

While lot of measurements describe the relaxation dynamics of the liquid state, experimental data of the glass dynamics at high temperatures are much scarcer. We use ultrafast scanning calorimetry to expand the timescales of the glass to much shorter values than previously achieved. Our data show that the relaxation time of glasses follows a super-Arrhenius behaviour in the high-temperature regime above the conventional devitrification temperature heating at 10 K/min. The liquid and glass states can be described by a common VFT-like expression that solely depends on temperature and limiting fictive temperature. We apply this common description to nearly-isotropic glasses of indomethacin, toluene and to recent data on metallic glasses. We also show that the dynamics of indomethacin glasses obey density scaling laws originally derived for the liquid. This work provides a strong connection between the dynamics of the equilibrium supercooled liquid and non-equilibrium glassy states.