Barium fluoride
Barium fluoride is an inorganic compound with the formula. It is a colorless solid that occurs in nature as the rare mineral frankdicksonite. Under standard conditions it adopts the fluorite structure and at high pressure the lead chloride| structure. Like Calcium fluoride|, it is resilient to and insoluble in water.
Above ca. 500 °C, is corroded by moisture, but in dry environments it can be used up to 800 °C. Prolonged exposure to moisture degrades transmission in the vacuum UV range. It is less resistant to water than calcium fluoride, but it is the most resistant of all the optical fluorides to high-energy radiation, though its far ultraviolet transmittance is lower than that of the other fluorides. It is quite hard, very sensitive to thermal shock and fractures quite easily.
Optical properties
Barium fluoride is transparent from the ultraviolet to the infrared, from 150 to 200 nm to 11–11.5 μm. It is used in windows for infrared spectroscopy, in particular in the field of fuel oil analysis. Its transmittance at 200 nm is relatively low, but at 500 nm it goes up to 0.96–0.97 and stays at that level until 9 μm, then it starts falling off. The refractive index is about 1.46 from 700 nm to 5 μm.Barium fluoride is also a common, very fast scintillators for the detection of X-rays, gamma rays or other high energy particles. One of its applications is the detection of 511 keV gamma photons in positron emission tomography. It responds also to alpha and beta particles, but, unlike most scintillators, it does not emit ultraviolet light. It can be also used for detection of high-energy neutrons, using pulse shape discrimination techniques to separate them from simultaneously occurring gamma photons.
Barium fluoride is used as a preopacifying agent and in enamel and glazing frits production. Its other use is in the production of welding agents. It is also used in metallurgy, as a molten bath for refining aluminium.