BaF₂-CaF₂-YF₃-AlF₃ Glass Systems for Infrared Transmission

Transparent and colorless glass rods have been obtained from the BaF 2 -CaF 2 -YF 3 -AlF 3 system, which consists of 15 to 27 mol% BaF 2 , 13 to 25 mol% CaF 2 , 6 to 28 mol% YF 3 and 37 to 50 mol% AlF 3 . Certain physical properties for the rods have been measured. Glass transition temperature, crystallization temperature, melting temperature and thermal expansion coefficient for 22BaF 2 -22CaF 2 -16YF 3 -40AlF 3 glass are determined as 430°C, 535°C, 710°C and 16.5×10 -6 /°C for 300–400°C, respectively. The glass is transparent at 0.23–5.2 µm wavelengths, and shows a refractive index ( n D ) of about 1.44, density of about 4.0 g/cm 3 , Knoop hardness of about 360 kg/mm 2 , and water solubility of about 0.005 g per 100 g cold water. These glass rods have been able to be drawn into trial fibers of a few meters in length.