Two types of structural relaxations around the deformation temperature of Ge20Sb15Se65 glass

Chalcogenide glasses have attracted a great deal of attention for the optical elements of infrared devices. The viscosity and elasticity of glasses are important characteristics for the use of precision molding techniques. The uniaxial compression creep behavior of Ge20Sb15Se65 glass was studied around its deformation temperature. The derived creep function was converted into relaxation moduli by Laplace transformation and its inversion. Analysis using a two-term Maxwell model revealed the shear relaxation modulus G(t) as two distinct structural relaxation processes with short and long relaxation times on the order of 101 s and 103 s, respectively, at 313 °C. The fast relaxation with high elasticity obeyed the time-temperature superposition principle and its activation energy ΔH1 was estimated to be 350 ± 10 kJ/mol using Narayanaswamy's relation. This energy is mainly comparable to the bond dissociation energies of SeSe (~320 kJ/mol). The process was therefore suggested to be due to motion around these thermally broken inter-atomic bonds, as in many glassy systems. In contrast, the low-elasticity slow relaxation process had activation energy of approximately 480 ± 60 kJ/mol and was considered to represent breaking and rearrangement of heteronuclear GeSe and SbSe bonds in the glass network during pressure-induced entanglement.