Meeting experimental challenges to physics of network glasses: assessing role of sample homogeneity

TL;DR

This study develops a Raman profiling method to monitor melt homogenization in Ge-Se glasses, revealing sharp elastic phase transitions that impact the fundamental physics of these network glasses.

Contribution

Introduces a real-time Raman profiling technique to assess melt homogenization and demonstrates the intrinsic sharp elastic transitions in Ge-Se glasses.

Findings

Melt homogenization at 950°C takes 168 hours for 2g samples.

Sharp rigidity and stress transitions occur at specific compositions.

Elastic phase transitions are intrinsic and influence glass physics.

Abstract

We introduce a Raman profiling method to track homogenization of Ge$_x$Se$_{100-x}$ melts in real time, and show that 2 gram melts reacted at 950{\deg}C in high vacuum homogenize in 168 hours on a scale of 10{\mu}m. Homogenization of melts is precursive to self-organization of glasses. In the present glasses, compositional variation of Raman active corner-sharing mode frequency of GeSe$_4$ units, molar volumes, and the enthalpy of relaxation at Tg, reveal the rigidity (xc(1)= 19.5(3)%) and the stress (xc(2) = 26.0(3)%) transitions to be rather sharp ({\Delta}x < 0.6%). These abrupt elastic phase transitions are intrinsic to these materials and have a direct bearing on physics of glasses.