BaF2 crystals or Barium Fluoride crystals, with their extremely broad transmission range from the deep UV to LWIR spectrum, are prevalent for Infrared applications requiring additional transmission in the Ultraviolet region. BaF2 crystals windows are excellent when being used for IR spectroscopes and as viewport windows for thermal imaging inspection in electric power facilities and petroleum industries. A low refractive index of 1.48 implies BaF2 windows have high transmission rates without anti-reflection coating.
BaF2 has similar properties to CaF2, the difference mainly lies in that barium fluoride is more resistant to highly energetic radiation, and with an equivalent thickness, the transmission range of BaF2 extends approximately 1 micron further into the long-wave IR region than calcium fluoride. BaF2 could also accommodate high-temperature environments up to 800 ℃. However, exposure to moisture will increase its sensitivity to temperature and reduce its transmission rate to UV lights.