Lithium fluoride

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Lithium fluoride
LiF-crystal.jPeG
Lithium-fluoride-3D-ionic.png
__ Li +     __ F −
NaCl polyhedra.png
__ Li +     __ F −
Names
IUPAC name
Lithium fluoride
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.029.229 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 232-152-0
PubChem CID
RTECS number
  • OJ6125000
UNII
  • InChI=1S/FH.Li/h1H;/q;+1/p-1 Yes check.svgY
    Key: PQXKHYXIUOZZFA-UHFFFAOYSA-M Yes check.svgY
  • InChI=1/FH.Li/h1H;/q;+1/p-1
    Key: PQXKHYXIUOZZFA-REWHXWOFAG
  • [Li+].[F-]
Properties
LiF
Molar mass 25.939(2) g/mol
AppearanceWhite powder or colorless hygroscopic crystals
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)
0.127 g/(100 mL) (18 °C)
0.134 g/(100 mL) (25 °C)
1.84×10−3 [1]
Solubility soluble in HF
insoluble in alcohol
−10.1·10−6 cm3/mol
1.3915
Structure
Face-centered cubic
a = 403.51 pm
Linear
Thermochemistry
1.507 J/(g·K)
Std molar
entropy (S⦵298)
35.73 J/(mol·K)
-616 kJ/mol
Hazards
GHS labelling:
GHS-pictogram-skull.svg
Danger
H301, H315, H319, H335 [2]
NFPA 704 (fire diamond)
NFPA 704.svgHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
3
0
0
Lethal dose or concentration (LD, LC):
143 mg/kg (oral, rat) [3]
Related compounds
Other anions
Lithium chloride
Lithium bromide
Lithium iodide
Lithium astatide
Other cations
Sodium fluoride
Potassium fluoride
Rubidium fluoride
Caesium fluoride
Francium fluoride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Yes check.svgY  verify  (what is  Yes check.svgYX mark.svgN ?)

Lithium fluoride is an inorganic compound with the chemical formula LiF. It is a colorless solid that transitions to white with decreasing crystal size. 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. [4] Partly because Li and F are both light elements, and partly because F2 is highly reactive, formation of LiF from the elements releases one of the highest energies per mass of reactants, second only to that of BeO.

Contents

Manufacturing

LiF is prepared from lithium hydroxide or lithium carbonate with hydrogen fluoride. [5]

Applications

Precursor to lithium hexafluorophosphate for batteries

Lithium fluoride is reacted with hydrogen fluoride (HF) and phosphorus pentachloride to make lithium hexafluorophosphate Li[PF6], an ingredient in lithium ion battery electrolyte.

The lithium fluoride alone does not absorb hydrogen fluoride to form a bifluoride salt. [6]

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 an Li-C-F interface on the carbon electrodes. [4] A useful molten salt, FLiNaK, consists of a mixture of LiF, together with sodium fluoride and potassium fluoride. The primary coolant for the Molten-Salt Reactor Experiment was FLiBe; 2LiF·BeF2 (66 mol% of LiF, 33 mol% of BeF2).

Optics

Because of the large band gap for LiF, its crystals are transparent to short wavelength ultraviolet radiation, more so than any other material. LiF is therefore used in specialized optics for the vacuum ultraviolet spectrum. [7] (See also magnesium fluoride.) Lithium fluoride is used also as a diffracting crystal in X-ray spectrometry.

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. 6LiF nanopowder enriched to 96% has been used as the neutron reactive backfill material for microstructured semiconductor neutron detectors (MSND). [8]

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 to 459 °C or 680 to 858 °F) 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 and OLEDs

Lithium fluoride is widely used in PLED and OLED as a coupling layer to enhance electron injection. The thickness of the LiF layer is usually around 1  nm. The dielectric constant (or relative permittivity, ε) of LiF is 9.0. [9]

Natural occurrence

Naturally occurring lithium fluoride is known as the extremely rare mineral griceite. [10]

Related Research Articles

<span class="mw-page-title-main">Hydrofluoric acid</span> Solution of hydrogen fluoride in water

Hydrofluoric acid is a solution of hydrogen fluoride (HF) in water. Solutions of HF are colorless, acidic and highly corrosive. A common concentration is 49% (48-52%) but there are also stronger solutions and pure HF has a boiling point near room temperature. It is used to make most fluorine-containing compounds; examples include the commonly used pharmaceutical antidepressant medication fluoxetine (Prozac) and the material PTFE (Teflon). Elemental fluorine is produced from it. It is commonly used to etch glass and silicon wafers.

Calcium fluoride is the inorganic compound of the elements calcium and fluorine with the formula CaF2. It is a white solid that is practically insoluble in water. It occurs as the mineral fluorite (also called fluorspar), which is often deeply coloured owing to impurities.

<span class="mw-page-title-main">Magnesium fluoride</span> Chemical compound of magnesium and fluorine

Magnesium fluoride is an ionically bonded inorganic compound with the formula MgF2. The compound is a white crystalline salt and is transparent over a wide range of wavelengths, with commercial uses in optics that are also used in space telescopes. It occurs naturally as the rare mineral sellaite.

<span class="mw-page-title-main">Sodium fluoride</span> Ionic compound (NaF)

Sodium fluoride (NaF) is an inorganic compound with the formula NaF. It is a colorless or white solid that is readily soluble in water. It is used in trace amounts in the fluoridation of drinking water to prevent tooth decay, and in toothpastes and topical pharmaceuticals for the same purpose. In 2021, it was the 291st most commonly prescribed medication in the United States, with more than 600,000 prescriptions. It is also used in metallurgy and in medical imaging.

<span class="mw-page-title-main">Molten-salt reactor</span> Type of nuclear reactor cooled by molten material

A molten-salt reactor (MSR) is a class of nuclear fission reactor in which the primary nuclear reactor coolant and/or the fuel is a mixture of molten salt with a fissionable material.

<span class="mw-page-title-main">Ammonium fluoride</span> Chemical compound

Ammonium fluoride is the inorganic compound with the formula NH4F. It crystallizes as small colourless prisms, having a sharp saline taste, and is highly soluble in water. Like all fluoride salts, it is moderately toxic in both acute and chronic overdose.

<span class="mw-page-title-main">Beryllium fluoride</span> Chemical compound

Beryllium fluoride is the inorganic compound with the formula BeF2. This white solid is the principal precursor for the manufacture of beryllium metal. Its structure resembles that of quartz, but BeF2 is highly soluble in water.

<span class="mw-page-title-main">Lithium hydride</span> Chemical compound

Lithium hydride is an inorganic compound with the formula LiH. This alkali metal hydride is a colorless solid, although commercial samples are grey. Characteristic of a salt-like (ionic) hydride, it has a high melting point, and it is not soluble but reactive with all protic organic solvents. It is soluble and nonreactive with certain molten salts such as lithium fluoride, lithium borohydride, and sodium hydride. With a molar mass of 7.95 g/mol, it is the lightest ionic compound.

<span class="mw-page-title-main">FLiNaK</span>

FLiNaK is the name of the ternary eutectic alkaline metal fluoride salt mixture LiF-NaF-KF (46.5-11.5-42 mol %). It has a melting point of 462 °C and a boiling point of 1570 °C. It is used as electrolyte for the electroplating of refractory metals and compounds like titanium, tantalum, hafnium, zirconium and their borides. FLiNaK also could see potential use as a coolant in the very high temperature reactor, a type of nuclear reactor.

<span class="mw-page-title-main">Hydrogen fluoride</span> Chemical compound

Hydrogen fluoride (fluorane) is an inorganic compound with chemical formula HF. It is a very poisonous, colorless gas or liquid that dissolves in water to yield an aqueous solution termed hydrofluoric acid. It is the principal industrial source of fluorine, often in the form of hydrofluoric acid, and is an important feedstock in the preparation of many important compounds including pharmaceuticals and polymers, e.g. polytetrafluoroethylene (PTFE). HF is also widely used in the petrochemical industry as a component of superacids. Due to strong and extensive hydrogen bonding, it boils at near room temperature, much higher than other hydrogen halides.

<span class="mw-page-title-main">Uranium tetrafluoride</span> Chemical compound

Uranium tetrafluoride is the inorganic compound with the formula UF4. It is a green solid with an insignificant vapor pressure and low solubility in water. Uranium in its tetravalent (uranous) state is important in various technological processes. In the uranium refining industry it is known as green salt.

<span class="mw-page-title-main">Ammonium bifluoride</span> Chemical compound

Ammonium bifluoride is the inorganic compound with the formula [NH4][HF2] or [NH4]F·HF. It is produced from ammonia and hydrogen fluoride. This colourless salt is a glass-etchant and an intermediate in a once-contemplated route to hydrofluoric acid.

<span class="mw-page-title-main">Zirconium tetrafluoride</span> Chemical compound

Zirconium(IV) fluoride describes members of a family inorganic compounds with the formula (ZrF4(H2O)x. All are colorless, diamagnetic solids. Anhydrous Zirconium(IV) fluoride' is a component of ZBLAN fluoride glass.

The bifluoride ion is an inorganic anion with the chemical formula [HF2]−. The anion is colorless. Salts of bifluoride are commonly encountered in the reactions of fluoride salts with hydrofluoric acid. The commercial production of fluorine involves electrolysis of bifluoride salts.

<span class="mw-page-title-main">Molten-Salt Reactor Experiment</span> Nuclear reactor, Oak Ridge 1965–1969

The Molten-Salt Reactor Experiment (MSRE) was an experimental molten-salt reactor research reactor at the Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee. This technology was researched through the 1960s, the reactor was constructed by 1964, it went critical in 1965, and was operated until 1969. The costs of a cleanup project were estimated at $130 million.

<span class="mw-page-title-main">Liquid fluoride thorium reactor</span> Type of nuclear reactor that uses molten material as fuel

The liquid fluoride thorium reactor is a type of molten salt reactor. LFTRs use the thorium fuel cycle with a fluoride-based molten (liquid) salt for fuel. In a typical design, the liquid is pumped between a critical core and an external heat exchanger where the heat is transferred to a nonradioactive secondary salt. The secondary salt then transfers its heat to a steam turbine or closed-cycle gas turbine.

<span class="mw-page-title-main">Potassium bifluoride</span> Chemical compound

Potassium bifluoride is the inorganic compound with the formula K[HF2]. This colourless salt consists of the potassium cation and the bifluoride anion. The salt is used as an etchant for glass. Sodium bifluoride is related and is also of commercial use as an etchant as well as in cleaning products.

<span class="mw-page-title-main">FLiBe</span> Chemical compound

FLiBe is the name of a molten salt made from a mixture of lithium fluoride (LiF) and beryllium fluoride. It is both a nuclear reactor coolant and solvent for fertile or fissile material. It served both purposes in the Molten-Salt Reactor Experiment (MSRE) at the Oak Ridge National Laboratory.

A monofluoride is a chemical compound with one fluoride per formula unit. For a binary compound, this is the formula XF.

<span class="mw-page-title-main">Sodium bifluoride</span> Chemical compound

Sodium bifluoride is the inorganic compound with the formula Na[HF2]. It is a salt of sodium cation and bifluoride anion. It is a white, water-soluble solid that decomposes upon heating. Sodium bifluoride is non-flammable, hygroscopic, and has a pungent smell. Sodium bifluoride has a number of applications in industry.

References

  1. ↑ John Rumble (June 18, 2018). CRC Handbook of Chemistry and Physics (99 ed.). CRC Press. pp. 5–188. ISBN   978-1138561632.
  2. ↑ "Lithium fluoride - Product Specification Sheet". Sigma-Aldrich. Merck KGaA. Retrieved 1 Sep 2019.
  3. ↑ "Lithium fluoride". Toxnet. NLM. Archived from the original on 12 August 2014. Retrieved 10 Aug 2014.
  4. 1 2 Aigueperse J, Mollard P, Devilliers D, et al. (2005). "Fluorine Compounds, Inorganic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a11_307. ISBN   9783527303854.
  5. ↑ Bellinger SL, Fronk RG, McNeil WJ, et al. (2012). "Improved High Efficiency Stacked Microstructured Neutron Detectors Backfilled With Nanoparticle 6LiF". IEEE Trans. Nucl. Sci. 59 (1): 167–173. Bibcode:2012ITNS...59..167B. doi:10.1109/TNS.2011.2175749. S2CID   19657691.
  6. ↑ Aigueperse, Jean; Mollard, Paul; Devilliers, Didier; Chemla, Marius; Faron, Robert; Romano, René; Cuer, Jean Pierre (2000). "Fluorine Compounds, Inorganic". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a11_307. ISBN   978-3527306732.
  7. ↑ "Lithium Fluoride (LiF) Optical Material". Crystran 19. 2012.
  8. ↑ McGregor DS, Bellinger SL, Shultis JK (2013). "Present status of microstructured semiconductor neutron detectors". Journal of Crystal Growth. 379: 99–110. Bibcode:2013JCrGr.379...99M. doi:10.1016/j.jcrysgro.2012.10.061. hdl: 2097/16983 .
  9. ↑ Andeen C, Fontanella J, Schuele D (1970). "Low-Frequency Dielectric Constant of LiF, NaF, NaCl, NaBr, KCl, and KBr by the Method of Substitution". Phys. Rev. B . 2 (12): 5068–73. Bibcode:1970PhRvB...2.5068A. doi:10.1103/PhysRevB.2.5068.
  10. ↑ "Griceite mineral information and data". Mindat.org. Archived from the original on 7 March 2014. Retrieved 22 Jan 2014.
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