- Calcium fluoride
ImageFileL1 = Calcium fluoride.jpg
ImageSizeL1 = 150 px
ImageFileR1 = Fluorite-unit-cell-3D-ionic.png
ImageSizeR1 = 150 px
ImageFile2 = Fluorid vápenatý.png
Section1 = Chembox Identifiers
CASNo = 7789-75-5
Section2 = Chembox Properties
Formula = CaF2
Appearance = White crystalline solid(single crystals are transparent) | Density = 3.18 ×103 kg/m3 (solid)
MeltingPtK = 1675
BoilingPtK = 2770
Solubility = virtually insoluble
Section3 = Chembox Structure
cubic crystal system, "cF12" [X-ray Diffraction Investigations of CaF2 at High Pressure, L. Gerward, J. S. Olsen, S. Steenstrup, M. Malinowski, S. Åsbrink and A. Waskowska, Journal of Applied Crystallography (1992), 25, 578-581 doi|10.1107/S0021889892004096]
SpaceGroup = Fm3m, #225
Coordination = Ca, 8, cubic
F, 4, tetrahedral
Section4 = Chembox Hazards
IngestionHazard = low
SkinHazard = low
InhalationHazard = low
EyeHazard = low
Calcium fluoride (CaF2) is an insoluble
ionic compound of calciumand fluorine. It occurs naturally as the mineral fluorite(also called fluorspar), and it is the source of most of the world's fluorine. This insoluble solid adopts a cubic structure wherein calcium is coordinated to eight fluoride anions and each F− ion is surrounded by four Ca2+ ions. [G. L. Miessler and D. A. Tarr “Inorganic Chemistry” 3rd Ed, Pearson/Prentice Hall publisher, ISBN 0-13-035471-6.] Although the pure material is colourless, the mineral is often deeply coloured due to the presence of F-centers.
ource of HF
Naturally occurring CaF2 is the principal source of
hydrogen fluoride, a commodity chemical used to produce a wide range of materials. Fluoride is liberated from the mineral by the action of concentrated sulfuric acid::CaF2(s) + H2SO4(l) → CaSO4(solid) + 2 HF(g)The resulting HF is converted into fluorine, fluorocarbons, and diverse fluoride materials. As of the late 1990s, five billion kilograms were mined annually. [Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.]
Calcium fluoride is commonly used as a window material for both
infraredand ultravioletwavelengths, since it is transparent in these regions (about 0.15 µm to 9 µm) and exhibits extremely weak birefringence. Furthermore the material is fairly inert chemically so that these windows are not attacked. Nevertheless, at wavelengths as low as 157 nm, which are interesting to semiconductormanufacturers, the birefringence of calcium fluoride exceeds tolerable limits. This problem with birefringence can be mitigated through optimised growth process. It is particularly important as an ultraviolet optical material for integrated circuitlithography. Canon also uses artificially-crystallized calcium fluoride components in some of its L-series lenses to reduce light dispersion. As an infrared optical material, calcium fluoride is sometimes known by the Eastman Kodaktrademarked name "Irtran-3," although this designation is obsolete. Uranium-doped calcium fluoride was the second type of solid state laserinvented, in the 1960s. Peter Sorokin and Mirek Stevenson at IBM's laboratories in Yorktown Heights(US) achieved lasing at 2.5 µm shortly after Maiman's ruby laser.
It is also used as a flux for melting and liquid processing of iron, steel and their composites. Its action is based on its similar melting point to iron, on its ability to dissolve oxides and on its ability to wet oxides and metals.
Fluorides are toxic to humans, however CaF2 is considered relatively harmless due to its extreme insolubility. The situation is analogous to BaSO4, where the toxicity normally associated with Ba2+ is offset by the very low solubility of its sulfate derivative.
List of laser types
* [http://webbook.nist.gov/cgi/cbook.cgi?ID=7789-75-5&Units=SI NIST webbook] thermochemistry data
* [http://www.stanford.edu/~siegman/cleo_plenary.pdf Uranium doped CaF2 laser] (pdf file)
* [http://www.press.uchicago.edu/Misc/Chicago/284158_townes.html Charles Townes on the history of lasers]
* [http://www.npi.gov.au/database/substance-info/profiles/44.html National Pollutant Inventory - Fluoride and compounds fact sheet]
* [http://www.physchem.ox.ac.uk/MSDS/CA/calcium_fluoride.html MSDS] (University of Oxford)
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