Effect of PbI2 on optical properties of Te-based far infrared transmitting chalcogenide glasses

A novel series of Ge-Te-PbI2 chalcogenide glasses is prepared by traditional melt-quenching method, and the glass-forming region is determined. X-ray diffraction, differential thermal analysis, visible/near-infrared absorption spectroscopy and infrared transmission spectra are adopted to analyze the composition, the structure, and the performance of the Te-based glasses system with an addition of PbI2. The Tauc equation is used to calculate the direct and the indirect optical band gaps, based on the metallization criterion and the band gap energy theory, the relationship between optical band gap and composition is investigated. The results show that with the addition of PbI2, the glasses-forming ability and the thermal stability are improved, Also, the density and the refractive index of glass sample both increase, the short-wavelength edges shift to ward a longer wavelength, the band gap decreases and the infrared cut-off wavelength of glass is 25 mu m which keeps almost unchanged. The series of glasses can be adopted to fabricate the far-IR optical wave-guide devices.