Synthesis and Characterization of the 25Ga2S3-(75 − x)
GeS2-xCsCl System for Engineering a Chemically 
Stable, Mid-IR Transparent Glass
Abstract25Ga2S3-(75 − x)GeS2-xCsCl (x = 5, 10, 15, 20, 25, 30, 35, 40, 45, and 50) compositions were synthesized and characterized. The glass-forming ability of each sample corresponds to the quantity of GeS2 and CsCl present in the sample. The density of the glasses sample was determined. Raman and Infrared (IR) spectra were conducted to determine the structures of the glasses. In the Raman spectra, the dominant GeS2 peak is assigned at ∼340 cm−1. As the CsCl content increases over 20 mol.%, the peak broadens and separates at ∼40 mol.% CsCl. As the CsCl content continues to increase, the intensity of the peak at ∼315 cm−1, which is assigned to Ga2S3-Cl, also increases. For the IR transmittance spectra of the glasses, five representative samples, 25Ga2S3-(75 − x)GeS2-xCsCl glasses (x = 5, 15, 30, 45, and 50), were prepared. As CsCl content increases, the absorption bands at 2.8 μm (3600 cm−1) and 6.3 μm (1600 cm−1), which are related to H2O, increases. The absorption band at 7.7 μm (1600 cm−1), which is assigned to OH− bonding, were not changed significantly with addition of CsCl. The Tg’s range from ∼400°C to 260°C as the amount of CsCl increases from 5 mol.% to 50 mol.%. The index of refraction of the Ga2S3-GeS2 system is ∼2.4, whereas the index of refraction of CsCl is ∼1.5. Therefore, by increasing the amount of CsCl in the system, the index of refraction decreases.