Strong Nature of the Melt in Under-Coordinated Se_80-xTe₂₀Sb_x Glasses

The under-coordinated Se_80-xTe₂₀Sb_x (0 ≤ x ≤ 10) glasses were synthesized by melt quenching, and their optical and thermal properties were studied. Modulated Differential Scanning Calorimetry (MDSC) was performed to understand the glass transition (T_g), reversing and non-reversing heat flows, the specific heat jump at T_g (ΔC_p), the strong and fragile nature of the melt, viscosity, and excess configurational entropy. T_g shows a continuous increase with the addition of antimony, suggesting that the structural network of Se_80-xTe₂₀Sb_x glasses becomes more polymerized. Notably, the Se₂Te₆ rings in the structural network open up with the incorporation of Sb. A change in slope in T_g at x = 5 may indicate a transformation of the structural network comprising rings and chains to a complete chain-like structure. The glass forming ability, thermal stability, ΔC_p, fragility, viscosity, and excess configurational entropy also exhibit a distinct change around x = 5. The near Arrhenius behavior of the viscosity with temperature indicates that the glass forming ability of Se_80-xTe₂₀Sb_x melts is strong. The band gap shifted toward lower energy with an increase in Sb, and the FTIR cutoff also shifted toward longer wavelengths with an increase in lower-energy Sb-Te bonds. Under-coordinated yet with a strong nature of melts, these glasses can be studied for different optoelectronic and infrared applications.