:Lanthanum trifluoride
{{chembox
| Watchedfields = changed
| verifiedrevid = 443382196
| Name = Lanthanum trifluoride
| ImageFile = Kristallstruktur Lanthanfluorid.png
| ImageFile2 =
| ImageCaption = Crystal structure
| OtherNames = Lanthanum(III) fluoride
|Section1={{Chembox Identifiers
| InChI = 1/La.3FH/h;3*1H/q+3;;;/p-3
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI =
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/La.3FH/h;3*1H/q+3;;;/p-3
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = BYMUNNMMXKDFEZ-UHFFFAOYSA-K
| SMILES = F[La](F)F
| InChIKey =
| CASNo = 13709-38-1
| CASNo_Ref = {{cascite|correct|CAS}}
| PubChem = 83675
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID =75498
| EC_number = 237-252-8
| RTECS =
}}
|Section2={{Chembox Properties
| Formula = LaF3
| MolarMass = 195.900 g/mol{{RubberBible92nd|page=4.69}}
| Appearance = white, crystalline solid
| Solubility =
| MeltingPtC = 1493
| MeltingPt_notes =
| RefractIndex = 1.606
| MagSus =
}}
|Section3={{Chembox Structure
| CrystalStruct = Rhombohedral, hR24
| LattConst_a = 0.7185 nm
| LattConst_c = 0.7351 nm
| UnitCellFormulas = 6
| UnitCellVolume =0.32865
}}
|Section4={{Chembox Hazards
| ExternalSDS = {{cite web |url= https://www.fishersci.com/shop/msdsproxy?productName=AC199170250&productDescription=LANTHANUM(III)-FLUORIDE%252C+25GR&catNo=AC19917-0250&vendorId=VN00032119&storeId=10652 |title= Safety Data Sheet: Lanthanum(III) fluoride |work= Thermo Fisher Scientific |date= 19 January 2018 |access-date= 17 August 2018 |archive-date= 17 August 2018 |archive-url= https://web.archive.org/web/20180817161248/https://www.fishersci.com/shop/msdsproxy?productName=AC199170250&productDescription=LANTHANUM(III)-FLUORIDE%252C+25GR&catNo=AC19917-0250&vendorId=VN00032119&storeId=10652 |url-status= dead }}
| GHSPictograms =
| NFPA_ref = pg 3
| NFPA-H = 2
| NFPA-F = 0
| NFPA-R = 0}}
| Section9 = {{Chembox Related
| OtherAnions = Lanthanum(III) chloride
Lanthanum(III) bromide
Lanthanum(III) iodide
| OtherCations = Actinium(III) fluoride
| OtherFunction =
| OtherFunction_label =
| OtherCompounds =
}}
}}
Lanthanum trifluoride is a refractory ionic compound of lanthanum and fluorine.{{cite book|author=Cotton, Simon |title=Lanthanide and Actinide Chemistry|url=https://books.google.com/books?id=SvAbtU6XvzgC&pg=PA26|date=30 January 2007|publisher=Wiley|isbn=978-0-470-01007-5|pages=25–27}} The chemical formula is {{chem|La|F|3}}.
The LaF<sub>3</sub> structure
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. At 300 K, the structure allows the formation of Schottky defects with an activation energy of 0.07 eV, and free flow of fluoride ions with an activation energy of 0.45 eV, making the crystal unusually electrically conductive.{{cite journal |last1=Frant |first1=Martin S. |last2=Ross |first2=James W. |title=Electrode for Sensing Fluoride Ion Activity in Solution |journal=Science |date=23 December 1966 |volume=154 |issue=3756 |pages=1553–1555 |doi=10.1126/science.154.3756.1553 |jstor=1720460 |pmid=5924922 |bibcode=1966Sci...154.1553F |s2cid=11042445 |url=https://www.jstor.org/stable/pdf/1720460.pdf}}{{cite journal |last1=Sher |first1=A. |last2=Solomon |first2=R. |last3=Lee |first3=K. |last4=Muller |first4=M. W. |title=Transport Properties of La F 3 |journal=Physical Review |date=15 April 1966 |volume=144 |issue=2 |pages=593–604 |doi=10.1103/PhysRev.144.593|bibcode=1966PhRv..144..593S }}
The larger sized rare earth elements (lanthanides), which are those with smaller atomic number, also form trifluorides with the LaF3 structure. Some actinides do as well.
Applications
This white salt{{anchor|la_fl_coating_anchor}} 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) {{nowrap|(100 nm < {{mvar|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. LaF{{sub|3}} is one of very few high-index materials in the far UV.{{cite book |last1=Rodríguez-de Marcos |first1=Luis |chapter=Multilayers and optical constants of various fluorides in the far UV |editor3-first=Detlev |editor3-last=Ristau |editor2-first=H. Angus |editor2-last=MacLeod |editor1-first=Michel |editor1-last=Lequime |date=23 September 2015 |title=Optical Systems Design 2015: Advances in Optical Thin Films V |series=Proceedings of SPIE |volume=9627 |pages=96270B |doi=10.1117/12.2191309 |bibcode=2015SPIE.9627E..0BR |chapter-url=http://spie.org/Publications/Proceedings/Paper/10.1117/12.2191309 |access-date=27 February 2019 |hdl=10261/134764 |s2cid=138737136 |hdl-access=free}} The material is also a component of multimetal fluoride glasses such as ZBLAN.{{cite web |author=Harrington, James A. |title=Infrared Fiber Optics |publisher=Rutgers University |url=http://irfibers.rutgers.edu/pdf_files/ir_fiber_review.pdf |url-status=dead |archive-url=https://web.archive.org/web/20080509143453/http://irfibers.rutgers.edu/pdf_files/ir_fiber_review.pdf |archive-date=2008-05-09}} It is also doped with europium(II) fluoride in fluoride selective electrodes.{{cite journal |last1=Light |first1=Truman S. |last2=Cappuccino |first2=Carleton C. |title=Determination of fluoride in toothpaste using an ion-selective electrode |journal=Journal of Chemical Education |date=April 1975 |volume=52 |issue=4 |pages=247–250 |doi=10.1021/ed052p247|pmid=1133123 |bibcode=1975JChEd..52..247L }}
Natural occurrence
LaF3 occurs in the nature as the extremely rare mineral fluocerite-(La).{{Cite web|url=https://www.mindat.org/min-1568.html|title=Fluocerite-(La)}}{{Cite web|url=https://www.ima-mineralogy.org/Minlist.htm|title=List of Minerals|date=21 March 2011}} 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)).{{cite journal |last1=Burke |first1=Ernst A.J.|date=2008 |title=Tidying up mineral names: an IMA-CNMNC scheme for suffixes, hyphens and diacrital marks|journal=Mineralogical Record |volume=39 |issue=2 |pages=131–135 |access-date=14 November 2020 | url=http://www.mineralogicalrecord.com}}
References
{{Commons category|Lanthanum(III) fluoride}}
{{reflist}}
{{Use dmy dates|date=March 2018}}
{{Lanthanum compounds}}
{{fluorides}}
{{Lanthanide halides}}