Thermal behavior of Se-rich Ge₂Sb₂Se_(5−y)Te_y chalcogenide system

Highlights: • Thermal behavior of the Ge₂Sb₂Se_(5−y)Te_y chalcogenide glasses was studied by DSC. • Full glass-forming region (compositions with y = 0, 0.5, and 1) was investigated. • Glass transition kinetics was described by the Tool–Narayanaswamy–Moynihan formalism. • Crystallization kinetics was described in terms of the Autocatalytic model. • Glass-forming ability was correlated with the determined P-type heat capacity dependences. - Abstract: The thermal behavior of the Ge₂Sb₂Se_(5−y)Te_y chalcogenide system (a compositional analog of the famous GST-225 PCM material) was thoroughly studied. Glass transition, cold crystallization, and melting phenomena were investigated in dependence on composition and various experimental conditions (heating rate, particle size). The kinetics of the structural relaxation and crystallization processes are described in terms of the Tool–Narayanaswamy–Moynihan and Autocatalytic models. The complexity of these processes is thoroughly discussed with regard to the compositionally given changes of molecular structures. Heat capacity measurements were performed for the compositions with y = 0, 0.5, and 1 in the 50–550 °C temperature range. All glassy and crystalline C_p dependences were found to be identical within the experimental error. The compositional dependence of the P-type undercooled liquid C_p evolution was found to contribute significantly to the changes in glass-forming ability (GFA). The GFA trend was discussed in terms of the mutual interplay between the thermodynamics and kinetics in this system