Competitive Phase Separation to Controllable Crystallization in 80 GeS 2 ·20 In 2 S 3 Chalcogenide Glass

Glass–ceramics of 80 GeS 2 ·20 In 2 S 3 were fabricated by heat‐treating the base glass at 402°C ( T g  + 30°C) for different durations. The glass–ceramics exhibited some improved mechanical properties such as hardness and resistance to crack propagation, and meanwhile remained an excellent infrared ( IR ) transmission. The XRD and R aman results showed that only In 2 S 3 crystals were precipitated inside glassy matrix. The evolution of two crystallization peaks ( CP s) in differential scanning calorimeter ( DSC ) curves were studied with samples heat‐treated at 402°C for different durations. It was found that the precipitation of In 2 S 3 crystal phase is responsible for the low‐temperature (first) CP , whereas the high‐temperature (second) CP shifts to a higher temperature with the elongation of the heat‐treatment duration. The crystallization of the higher temperature phase was inhibited with the precipitation of In 2 S 3 . Furthermore, crystallization mechanism was investigated using the nonisothermal method. The computed results showed that strictly more energy (higher activation energy, E c ) is essential for the precipitation of the higher temperature phase, which is in accordance with the DSC study of crystallized samples. More noticeable, the crystallization rate constant ( K ) value of 6.639 × 10 −8  s −1 for the second CP is ~ 5 orders of magnitude smaller than that of the In 2 S 3 phase, and this significant difference makes the crystallization of higher temperature crystal phase very hard. Consequently, controllable crystallization of 80 GeS 2 ·20 In 2 S 3 chalcogenide glass–ceramics with sole In 2 S 3 crystallites can be achieved easily.