The correlation between structural and optical properties of Ge-Sb-Se glassy system was the goal of this study. In this regards, several Se60Ge40-xSbx (0≤x≤25) glasses were prepared by conventional melt quenching technique. The prepared samples were characterized using X-ray diffraction (XRD), differential thermal analysis (DTA), ultraviolet- visible (UV-Vis-NIR) and Fourier transform infrared (FTIR) spectroscopy. The fundamental absorption edge for all the glasses was analyzed in terms of the theory proposed by Davis and Mott. According to achieved results, fully amorphous phase can easily form in different Ge-Sb-Se systems. The glass transition temperature and optical energy gap of the glassy Ge40Se60 were estimated about 340 oC and 1.28 e.V., respectively. The addition of antimony has deleterious effects on thermal and optical behaviors of Ge40Se60 glass. By increasing the antimony content up to 25 mole%, the glass transition temperature reaches to about 249 oC. In this condition, the optical energy gap as well as IR transparency decreases to about zero. In fact, the Se60Ge15Sb25 is opaque in infrared region.
