Phase Separation in Nonstoichiometry Ge–Sb–S Chalcogenide Glasses

A series of (1 ? x)GeS_2.5 – xSb chalcogenide glasses were prepared using the conventional melt‐quenching method. Their microstructure and thermal response were systematically studied. We observe a compositional threshold of x = 0.25 which corresponds to chemical stoichiometric composition in the calorimetric experiments. It is in good accordance with the Raman scattering results and laser‐induced phase transformation behavior. They also indicate that phase separation of Sb‐rich phase exists in the S‐poor samples. Moreover, we got a structural modeling of this phase separation: (1) at x = 0.25, which is chemical stoichiometric composition, the structural motifs are only SbS₃ pyramid and GeS₄ tetrahedra, and the three‐coordinated SbS₃ pyramid is isolated by GeS₄ tetrahedra; (2) at x < 0.25, the S–S bonds exist in the glass network due to the excess of S; and (3) at x > 0.25, the excess of Sb break the Ge–S and Sb–S bonds to form Sb(Ge)–Sb Bonds, and the Sb atoms segregate from the backbone to nucleate a separate Sb‐rich phase. This work provides a new way to investigate the phase separation of glass networks and helps us to better understand their related physical properties.