Ga-Sb-S glasses: Synthesis, properties and structural insights from Raman spectroscopy, high-energy XRD and DFT modelling

• Enhanced structural compaction with Ga₂S₃ addition. • Non-monotonic thermal and electrical trends. • Raman and DFT analyses revealed a transition from Sb-centred pyramidal units to Ga-centered tetrahedral units as x increased beyond 0.2. • High-energy XRD and DFT confirmed the presence of Ga–Ga homopolar bonds (e.g., ETH-Ga₂S₆-like units) influencing local network connectivity. The Ga₂S₃–Sb₂S₃ quasi-binary system has been investigated for its potential to yield stable chalcogenide glasses with tailored thermal and structural properties. Using melt-quenching techniques, a series of (Ga₂S₃) ₓ (Sb₂S₃)₁₋ ₓ compositions (0.0 ≤ x ≤ 0.5) were synthesized, and their glass-forming domain was mapped. The latter extends up to approximately x ≤ 0.40, as confirmed by X-ray diffraction and DSC analyses, with the x = 0.4 composition exhibiting a glass-ceramic character. Density measurements, combined with calculations of molar volume and packing density, revealed a continuous structural densification as Ga₂S₃ content increased. Differential scanning calorimetry showed an increase in glass transition temperature ( T g ), with the best thermal stability observed for x = 0.2, as assessed by the Hruby criterion. Electrical conductivity measurements demonstrated thermally activated behaviour following the Arrhenius law, with maximum activation energy also centred at x = 0.2. Raman spectroscopy and DFT modelling were used to decipher the structural contributions of Sb–S and Ga–S bonding. The emergence of vibrational modes characteristic of Ga-based structural units, especially beyond x > 0.2, suggests a structural reorganization from Sb-centred pyramidal units to Ga-centred tetrahedral. This was corroborated by high-energy X-ray diffraction, which showed significant changes in intermediate-range order with increasing Ga content, particularly in the first sharp diffraction peak and partial coordination environments.