Lithium fluoride
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| Names | |
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| IUPAC name
Lithium fluoride
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| Identifiers | |
3D model (JSmol)
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| ChemSpider | |
| ECHA InfoCard | 100.029.229 |
| EC Number |
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PubChem CID
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| RTECS number |
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CompTox Dashboard (EPA)
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| Properties | |
| 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 (1,553 °F; 1,118 K) |
| Boiling point | 1,676 °C (3,049 °F; 1,949 K) |
| 0.27 g/100 mL (18 °C)[1] | |
| Solubility | soluble in HF insoluble in alcohol |
Refractive index (nD)
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1.39937 |
| Structure | |
| Cubic | |
| Linear | |
| Thermochemistry | |
Heat capacity (C)
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1.604 J/(g K) |
Std molar
entropy (S⦵298) |
1.376 J/(g K) |
Std enthalpy of
formation (ΔfH⦵298) |
-23.75 kJ/g |
| Hazards | |
| NFPA 704 (fire diamond) | |
| Related compounds | |
Other anions
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Lithium chloride Lithium bromide Lithium iodide |
Other cations
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Sodium fluoride Potassium fluoride Rubidium fluoride Caesium fluoride |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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]
Applications
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.
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)
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.
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.
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.
References
- ^ "Lithium fluoride". 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". Retrieved 2010-12-28.