Abrupt boundaries of intermediate phases and space filling in oxide glasses

TL;DR

This study investigates the structural and elastic properties of sodium germanate glasses, revealing sharp boundaries of intermediate phases and their correlation with reversibility and volume anomalies, using various spectroscopic and mechanical measurements.

Contribution

It identifies abrupt boundaries of intermediate phases in oxide glasses and correlates them with reversibility and volume minima, providing new insights into glass network transitions.

Findings

Reversibility window observed between 14% and 19% Na2O content.

Anomalies in Raman and IR modes indicate stress and rigidity transitions.

Birefringence confirms stress-free nature of the intermediate phase.

Abstract

Modulated DSC measurements on bulk (Na2O)x(GeO2)1-x glasses show a sharp reversibility window in the 14% < x < 19% soda range, which correlates well with a broad global minimum in molar volumes. Raman and IR reflectance TO and LO mode frequencies exhibit anomalies between xc(1) = 14% (stress transition) and xc(2) = 19% (rigidity transition), with optical elasticity power-laws confirming the nature of the transitions . Birefringence measurements dramatize the macroscopically stress-free nature of the Intermediate Phase in the reversibility window.