Glass transition kinetics and crystallization mechanism in Ge–Ga–S–CsCl chalcohalide glasses

• Glass transition and crystallization kinetics of chalcohalide glasses were studied by DSC.
• Two crystalline phases (Ga2S3 and Ge2S) were identified after annealing.
• Ga2S3 crystals grow in two dimensions in the studied glasses.

The glass transition and the crystallization kinetics of 70Ge2S–10Ga2S3–20CsCl and 37.5Ge2S–22.5Ga2S3–40CsCl chalcohalide glasses were studied by using a differential scanning calorimeter (DSC) under non-isothermal conditions and X-ray diffraction (XRD) techniques. Two crystalline phases (Ga2S3 and Ge2S) were identified after annealing the chalcohalide glasses at the temperature corresponding to the crystallization peaks for 2 h. All the characteristic temperatures such as glass transition (Tg), crystallization onset (Tc) and crystallization peak (Tp) temperatures were found to depend on both the heating rate and the composition.Two approaches, namely Moynihan and Kissinger, were used to calculate the relaxation activation energy (Et). In addition, characteristic activation energies (Ec) and Avrami exponents (n) were obtained and analyzed by using Kissinger's relation, Ozawa's method, the Augis–Bennett approximation and the Matusita–Sakka theory.