Melt homogenization and self-organization of chalcogenides glasses: evidence of sharp rigidity, stress and nanoscale phase separation transitions in the GexSe100-x binary

TL;DR

This study uses Raman profiling to investigate the homogenization, phase transitions, and aging behaviors in GexSe100-x chalcogenide glasses, revealing sharp rigidity and stress transitions and the importance of sample homogeneity.

Contribution

It provides new insights into the rigidity and stress transitions, phase separation, and aging phenomena in GexSe glasses, emphasizing the role of homogeneity in their physical behavior.

Findings

Rigidity transition near 19.5% Ge content.

Stress transition near 26% Ge content.

Aging of non-reversing enthalpy outside the Intermediate Phase.

Abstract

A Raman profiling method is used to monitor growth of GexSe100-x melts and reveals a two step process of homogenization. Resulting homogeneous glasses show the non-reversing enthalpy at Tg, {\Delta}Hnr(x), to show a square-well like variation with x, with a rigidity transition near xc(1) = 19.5(5)% and stress transition near xc(2) = 26.0(5)%) representing the boundaries of the rigid but stress-free Intermediate Phase (IP). The square-well like variation of {\Delta}Hnr(x) develops sloping walls, a triangular shape and eventually disappears in glasses having an increasing heterogeneity. The {\Delta}Hnr term ages over weeks outside the IP but not inside the IP. An optical analogue of the reversibility window is observed with Raman spectra of as-quenched melts and Tg cycled glasses being the same for glass compositions in the IP but different for compositions outside the IP. Variations of Molar volumes, display three regimes of behavior with a global minimum in the IP and a pronounced increase outside that phase. The intrinsic physical behavior of dry and homogeneous chalcogenides glasses can vary sharply with composition near elastic and chemical phase transitions, showing that the physics of network glasses requires homogeneous samples, and may be far more interesting than hitherto recognized.