Magnesium fluoride is an ionically bonded inorganic compound with the formula MgF2. The compound is a colorless to 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.
Production
Magnesium fluoride is prepared from magnesium oxide with sources of hydrogen fluoride such as ammonium bifluoride, by the breakdown of it:
MgO + [NH4]HF2 → MgF2 + NH3 + H2ORelated metathesis reactions are also feasible:
Mg(OH)2 + CuF2 → MgF2 + Cu(OH)2Structure
The compound crystallizes as tetragonal birefringent crystals. The structure of the magnesium fluoride is similar to that of rutile,12 featuring octahedral Mg2+ cations and 3-coordinate F− anions.3
Coordination geometry in magnesium fluoride4| Magnesium coordination | Fluorine coordination |
|---|---|
In the gas phase, monomeric MgF2 molecules adopt a linear molecular geometry.56
Uses
Optics
Magnesium fluoride is transparent over an extremely wide range of wavelengths. Windows, lenses, and prisms made of this material can be used over the entire range of wavelengths from 0.120 μm (vacuum ultraviolet) to 8.0 μm (infrared). High-quality, synthetic magnesium fluoride is one of two materials (the other being lithium fluoride) that will transmit in the vacuum ultraviolet range at 121 nm (Lyman alpha).
Magnesium fluoride is tough and polishes well but is slightly birefringent and should therefore be cut with the optic axis perpendicular to the plane of the window or lens.7 Due to its suitable refractive index of 1.37, magnesium fluoride is commonly applied in thin layers to the surfaces of optical elements as an inexpensive anti-reflective coating. Its Verdet constant is 0.00810 arcmin⋅G−1⋅cm−1 at 632.8 nm.8
Safety
Chronic exposure to magnesium fluoride may affect the skeleton, kidneys, central nervous system, respiratory system, eyes and skin, and may cause or aggravate attacks of asthma.9
External links
- Infrared windows at Lawrence Berkeley National Laboratory
- National Pollutant Inventory - Fluoride and compounds fact sheet
- Crystran Data Crystran MSDS[permanent dead link]
References
Wells, A. F. (1984). Structural Inorganic Chemistry (5th ed.). Oxford University Press. pp. 413, 441. ISBN 978-0-19-965763-6. 978-0-19-965763-6 ↩
Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 117–119. ISBN 978-0-08-037941-8. 978-0-08-037941-8 ↩
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 3527306730. 3527306730 ↩
Haines, J.; Léger, J. M.; Gorelli, F.; Klug, D. D.; Tse, J. S.; Li, Z. Q. (2001). "X-ray diffraction and theoretical studies of the high-pressure structures and phase transitions in magnesium fluoride". Phys. Rev. B. 64 (13): 134110. Bibcode:2001PhRvB..64m4110H. doi:10.1103/PhysRevB.64.134110. /wiki/Physical_Review_B ↩
Wells, A. F. (1984). Structural Inorganic Chemistry (5th ed.). Oxford University Press. pp. 413, 441. ISBN 978-0-19-965763-6. 978-0-19-965763-6 ↩
Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 117–119. ISBN 978-0-08-037941-8. 978-0-08-037941-8 ↩
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 3527306730. 3527306730 ↩
J. Chem. Soc., Faraday Trans., 1996, 92, 2753 - 2757. doi:10.1039/FT9969202753 /wiki/Doi_(identifier) ↩
"Magnesium Fluoride Material Safety Data Sheet". ESPI Metals. August 2004. Archived from the original on 2017-10-28. Retrieved October 13, 2017. https://web.archive.org/web/20171028013735/http://www.espimetal.com/index.php/msds/658-Magnesium%20Fluoride ↩