Lithium fluoride
| Lithium fluoride | |
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Lithium fluoride |
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| Identifiers | |
| CAS number | 7789-24-4  |
| PubChem | 224478 |
| ChemSpider | 23007 |
| EC number | 232-152-0 |
| RTECS number | OJ6125000 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | LiF |
| Molar mass | 25.939(2) g/mol |
| Appearance | white powder or transparent crystals, non-hygroscopic |
| Density | 2.635 g/cm3 |
| Melting point |
845 °C, 1118 K, 1553 °F |
| Boiling point |
1676 °C, 1949 K, 3049 °F |
| Solubility in water | 0.27 g/100 mL (18 °C)[1] |
| Solubility | soluble in HF insoluble in alcohol |
| Refractive index (nD) | 1.39937 |
| Structure | |
| Crystal structure | Cubic |
| Molecular shape | Linear |
| Thermochemistry | |
| Std enthalpy of formation ΔfH |
-23.75 kJ/g |
| Standard molar entropy S |
1.376 J/(g K) |
| Specific heat capacity, C | 1.604 J/(g K) |
| Hazards | |
| NFPA 704 |
 0
2
0
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| Related compounds | |
| Other anions | Lithium chloride Lithium bromide Lithium iodide |
| Other cations | Sodium fluoride Potassium fluoride Rubidium fluoride Caesium fluoride |
 (verify) (what is:  / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Lithium fluoride is an inorganic compound with the formula LiF. It is the lithium salt of hydrofluoric acid. This white solid is a simple ionic compound. Its structure is analogous to that of sodium chloride, but it is much less soluble in water. It is mainly used as a component of molten salts.[2]
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[edit] Applications
[edit] In molten salts
Fluorine is produced by the electrolysis of molten potassium bifluoride. This electrolysis proceeds more efficiently when the electrolyte contains a few percent of LiF, possibly because it facilitates formation of Li-C-F interface on the carbon electrodes.[2] A useful molten salt consists of a mixture of LiF, together with sodium fluoride and potassium fluoride.
[edit] Optics
Because of its large band gap, LiF crystals are transparent to short wavelength ultraviolet radiation, more so than any other material. LiF is therefore used in specialized UV optics,[3] (See also magnesium fluoride)
[edit] Radiation detectors
It is also used as a means to record ionizing radiation exposure from gamma rays, beta particles, and neutrons (indirectly, using the 6
3Li (n,alpha) nuclear reaction) in thermoluminescent dosimeters.
[edit] Nuclear reactors
Lithium fluoride (highly enriched in the common isotope lithium-7) forms the basic constituent of the preferred fluoride salt mixture used in liquid-fluoride nuclear reactors. Typically lithium fluoride is mixed with beryllium fluoride to form a base solvent (FLiBe), into which fluorides of uranium and thorium are introduced. Lithium fluoride is exceptionally chemically stable and LiF/BeF2 mixtures (FLiBe) have low melting points (360 C - 459 C) and the best neutronic properties of fluoride salt combinations appropriate for reactor use. MSRE used two different mixtures in the two cooling circuits.
[edit] Cathode for PLED
Lithium fluoride is widely used in PLED as a coupling layer to enhance electron injection. The thickness of LiF layer is usually around 1 nm.
[edit] References
- ^ "Lithium fluoride". http://webbook.nist.gov/cgi/cbook.cgi?ID=C7789244&Units=SI. Retrieved 2006-02-26.
- ^ a b J. Aigueperse, P. Mollard, D. Devilliers, M. Chemla, R. Faron, R. Romano, J. P. Cuer, “Fluorine Compounds, Inorganic” in Ullmann’s Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. doi:10.1002/14356007.a11_307.
- ^ "Crystran Ltd., a manufacturer of infrared and ultraviolet optics". http://www.crystran.co.uk/lithium-fluoride-lif.htm. Retrieved 2010-12-28.
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