Ergodicity breaking of an inorganic glass in aging near ${T_g}$ probed by elasticity relaxation

TL;DR

This study investigates aging in inorganic glass near its glass transition temperature, revealing ergodicity breaking and demonstrating Kovacs' paradox through elasticity relaxation measurements.

Contribution

It provides the first experimental evidence of Kovacs' paradox in inorganic glasses and links relaxation dynamics to ergodicity breaking near ${T_g}$.

Findings

Relaxation of Young's modulus is exponential with a ${T_1}$-dependent relaxation time.

Demonstration of Kovacs' paradox in inorganic glasses.

Identification of a critical temperature ${T_p \\sim T_g}$ where relaxation behavior changes.

Abstract

We performed a series of aging experiments of an inorganic glass (As${_2}$Se${_3}$) at a temperature ${T_2}$ near the glass transition point ${T_g}$ by first relaxing it at ${T_1}$. The relaxation of Young's modulus was monitored, which was(almost if not ideally) exponential with a ${T_1}$-dependent relaxation time ${\tau(T_1)}$. We demostrate the Kovacs' paradox for the first time in an inorganic glasses. Associated with the divergence of ${\tau}$, the quasi-equilibrated Young's modulus ${E_\infty}$ does not converge either. An elastic model of relaxation time and a Mori-Tanaka analysis of ${E_\infty}$ lead to a similar estimate of the persistent memory of the history, ergodicity breaking within the accessible experimental time. Experiments with different ${T_2}$ exhibits a critical temperature ${T_p \sim T_g}$, i.e., when ${T_2 > T_p}$, both ${\tau}$ and ${E_\infty}$ converge.