Barium Fluoride (BaF2)
Barium Fluoride is a chemical compound of barium and fluorine, also known as Barium (II) fluoride.
In its crystalline form, barium fluoride is a common, very fast (one of the fastest) scintillators for the detection of X-rays, gamma rays or other high energy particles. It responds also to alpha and beta particles, but, unlike most scintillators, it glows in ultraviolet light. Also, it can be used for detection of high-energy neutrons.
When heated to 500o C it corrodes in water, but in a dry environment, it can be used up to 800o C. Prolonged exposure to moisture degrades transmission in the vacuum UV range. It is less resistant to water than calcium fluoride, but is the most resistant of all the optical fluorides to high-energy radiation, though its far ultraviolet transmittance is lower. It is quite hard, and very sensitive to thermal shock.