Similar behaviors of sulfide and selenide-based chalcogenide glasses to form glass-ceramics

In this paper, the strong influence of alkali halide in chalcogenide glasses is reminded, leading for the first time to highly transparent glasses from the visible range up to 11 mu m. The behavior of crystallization has been demonstrated to be similar in sulfide and selenide glasses containing gallium as well. The structural evolution of several glass compositions from the Ge-Ga-S or Ge-Ga-Se systems leading to reproducible glass-ceramics has been studied by XRD, NMR and thermal analysis. Whatever the composition, gallium plays a fundamental role as nanosized domains appear by phase separation between Ge rich regions and Ga rich regions. The determination of the appropriate crystallization time and temperature has permitted to obtain new passive and active glass-ceramics with a broadened transmittance region thanks to the incorporation of various alkali halides. In the first case, the controllable generation of nanocrystals leads to an increase of the main thermo-mechanical properties. In the second case, the incorporation of rare-earth ions inside the glass-ceramics has exacerbated their photoluminescence properties. The possibility to combine the ceramization process with the shaping has also been demonstrated.