Lanthanum trifluoride

Lanthanum trifluoride is a refractory ionic compound of lanthanum and fluorine.[4]

Lanthanum trifluoride

Crystal structure
Names
Other names
Lanthanum(III) fluoride
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.033.851
EC Number
  • 237-252-8
Properties
LaF3
Molar mass 195.900 g/mol[1]
Appearance white, crystalline solid
Density 5.9 g/cm3[1]
Melting point 1,493 °C (2,719 °F; 1,766 K)[1]
1.606
Structure
Rhombohedral, hR24
P3c1, No. 165[2]
a = 0.7185 nm, c = 0.7351 nm
0.32865
6
Hazards
Safety data sheet [3]
NFPA 704 (fire diamond)
[3] pg 3
Flammability code 0: Will not burn. E.g. waterHealth code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
0
2
0
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

The LaF3 structure
Lanthanum coordination

Bonding is ionic with lanthanum highly coordinated. The cation sits at the center of a trigonal prism. Nine fluorine atoms are close: three at the bottom corners of the trigonal prism, three in the faces of the trigonal prism, and three at top corners of the trigonal prism. There are also two fluorides a little further away above and below the prism. The cation can be considered 9-coordinate or 11-coordinate.[4]

The larger sized rare earth elements (lanthanides), which are those with smaller atomic number, also form trifluorides with the LaF3 structure.[4] Some actinides do as well.

Applications

Lanthanum fluoride is sometimes used as the "high-index" component in multilayer optical elements such as ultraviolet dichroic and narrowband mirrors. Fluorides are among the most commonly used compounds for UV optical coatings due to their relative inertness and transparency in the far ultraviolet (FUV) (100 nm < λ < 200 nm). Multilayer reflectors and antireflection coatings are typically composed of pairs of transparent materials, one with a low index of refraction, the other with a high index. There are very few high-index materials in the far UV. LaF3 is one.[5] The material is also a component of multimetal fluoride glasses such as ZBLAN.[6] It is also used (with europium fluoride, EuF2) in fluoride selective electrodes.

Natural occurrence

LaF3 occurs in the nature as the extremely rare mineral fluocerite-(La).[7][8] The suffix in the name is known as the Levinson modifier and, by showing the dominant element at a particular site in the structure, is used to differentiate from similar minerals (here: fluocerite-(Ce)).[9]

References
  1. Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.69. ISBN 1439855110.
  2. Zalkin, A.; Templeton, D. H. (1985). "Refinement of the trigonal crystal structure of lanthanum trifluoride with neutron diffraction data" (PDF). Acta Crystallographica Section B. 41 (2): 91. doi:10.1107/S0108768185001689.
  3. "Safety Data Sheet: Lanthanum(III) fluoride". Thermo Fisher Scientific. 19 January 2018. Retrieved 17 August 2018.
  4. Cotton, Simon (30 January 2007). Lanthanide and Actinide Chemistry. Wiley. pp. 25–27. ISBN 978-0-470-01007-5.
  5. Rodríguez-de Marcos, Luis (23 September 2015). Lequime, Michel; MacLeod, H. Angus; Ristau, Detlev (eds.). "Multilayers and optical constants of various fluorides in the far UV". Proceedings of SPIE: Advances in Optical Thin Films V. Optical Systems Design 2015: Advances in Optical Thin Films V. 9627 (B0): 96270B. doi:10.1117/12.2191309. hdl:10261/134764. S2CID 138737136. Retrieved 27 February 2019.
  6. Harrington, James A. "Infrared Fiber Optics" (PDF). Rutgers University. Archived from the original (PDF) on 9 May 2008.
  7. https://www.mindat.org/min-1568.html
  8. https://www.ima-mineralogy.org/Minlist.htm
  9. Burke, Ernst A.J. (2008). "Tidying up mineral names: an IMA-CNMNC scheme for suffixes, hyphens and diacrital marks". Mineralogical Record. 39 (2): 131–135. Retrieved 14 November 2020.


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