This work focuses on the study of the physical aging of a selenium glass by differential scanning calorimetry (DSC) and fast scanning calorimetry (FSC). Aged samples of 30 and 40 years old at room temperature were analysed by classical DSC, and their enthalpies of recovery were calculated, showing that the glass has reached its thermodynamic equilibrium and is stable over time. The study of accelerated physical aging by using FSC on a rejuvenated sample allows reproducing the way by which this glass has reached its thermodynamic equilibrium at the laboratory time scale. We evidence that the glass reaches its equilibrium state in one or two steps, depending on the gap between the aging temperature and the glass transition temperature, resulting from the difference in the mechanisms governing the relaxation process. Furthermore, a second phenomenon is evidenced, consisting in the crystallization of the glass once the equilibrium has been reached for aging temperatures close to the glass transition temperature.
TOC graphicCrystallisation of a 62,5GeS2-12,5Sb2S3-25CsCl glass-ceramic was investigated using different techniques from macro to nano-scale. A two-step crystallization process was evidenced, allowing a direct correlation between the microstructural features and the evolution of the mechanical and optical properties. This two-step crystallization process starts with the nucleation of spherical CsCl crystals that progressively evolve toward a disc shaped morphology when they grow. This transformation goes along with a local enrichment of Sb leading also to a significant increase of the lattice parameter of the CsCl phase. These crystals significantly improve the mechanical behaviour of the glass with only a small reduction of the infrared transmission properties.
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