Thorium tetrafluoride

Thorium(IV) fluoride (ThF4) is an inorganic chemical compound. It is a white, hygroscopic powder which can be produced by reacting thorium with fluorine gas. At temperatures above 500 °C, it reacts with atmospheric moisture to produce ThOF2. Thorium(IV) fluoride (ThF4) is an inorganic chemical compound. It is a white, hygroscopic powder which can be produced by reacting thorium with fluorine gas. At temperatures above 500 °C, it reacts with atmospheric moisture to produce ThOF2. Despite its (mild) radioactivity, thorium fluoride is used as an antireflection material in multilayered optical coatings. It has excellent optical transparency in the range 0.35–12 µm, and its radiation is primarily due to alpha particles, which can be easily stopped by a thin cover layer of another material. Thorium fluoride was used in manufacturing carbon arc lamps, which provided high-intensity illumination for movie projectors and search lights.