Investigation of physical ageing effect in Se₉₀In₄Sn₆ glass

Physical ageing effect in ternary Se₉₀In₄Sn₆ glass has been detected, using differential scanning calorimeter (DSC), under the influence of Co⁶⁰ γ-irradiation, natural storage, and both. The number of Lagrangian constraints per atom (n_c) of the investigated Se₉₀In₄Sn₆ glass comes out to be 2.9. This reveals that the studied material belongs to a floppy glass with under-constrained glassy network and hence one expects it to undergo physical ageing effect. It is observed that γ-irradiation increases the glass transition temperature T_g and the endothermic peak area A, which is directly related to the relaxation enthalpy loss. The estimated value of A of γ-irradiated glass is slightly higher than that of un-irradiated glass, indicating that thermodynamic equilibrium state of super-cooled liquid is still not reached and further storage is required. In addition, pure natural storage increases also the two ageing parameters (T_g and A) where the value of A is nearly four times greater than that of un-irradiated glass. This indicates that a significant natural ageing effect is evident in the studied glass and a structural relaxation process towards a more equilibrium state can be attained. Moreover, for γ-irradiated Se₉₀In₄Sn₆ glass which has been aged for 8 years, a small increase in the A value is evident, which reveals that γ-irradiation modifies its covalent-bonded glass network towards thermodynamically equilibrium extrapolated states of super-cooled liquid. - Highlights: • Untreated Se₉₀In₄Sn₆ glass undergoes physical ageing upon natural storage. • γ-irradiation accelerates the relaxation process in the studied glass. • Natural storage of irradiated glass yields a more structurally stable state