Lanthanum trifluoride is a refractory ionic compound of lanthanum and fluorine.^[4] The chemical formula is LaF
₃.

Quick Facts Names, Identifiers ...

Lanthanum trifluoride

Crystal structure
Names
Other names Lanthanum(III) fluoride
Identifiers
CAS Number	13709-38-1 Y
3D model (JSmol)	Interactive image
ChemSpider	75498 Y
ECHA InfoCard	100.033.851
EC Number	237-252-8
PubChem CID	83675
CompTox Dashboard (EPA)	DTXSID2065591
InChI InChI=1S/La.3FH/h;3*1H/q+3;;;/p-3 Y Key: BYMUNNMMXKDFEZ-UHFFFAOYSA-K Y InChI=1/La.3FH/h;3*1H/q+3;;;/p-3
SMILES F[La](F)F
Properties
Chemical formula	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]
Refractive index (nD)	1.606
Structure
Crystal structure	Rhombohedral, hR24
Space group	P3c1, No. 165[2]
Lattice constant	a = 0.7185 nm, c = 0.7351 nm
Lattice volume (V)	0.32865
Formula units (Z)	6
Hazards
NFPA 704 (fire diamond)	[3] pg 3 2 0 0
Safety data sheet (SDS)	[3]
Related compounds
Other anions	Lanthanum(III) chloride Lanthanum(III) bromide Lanthanum(III) iodide
Other cations	Actinium(III) fluoride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Close

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] 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.^[5][6]

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.

This white salt 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. LaF₃ is one of very few high-index materials in the far UV.^[7] The material is also a component of multimetal fluoride glasses such as ZBLAN.^[8] It is also doped with europium(II) fluoride in fluoride selective electrodes.^[9]

LaF₃ occurs in the nature as the extremely rare mineral fluocerite-(La).^[10][11] 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)).^[12]