Cerium(III) fluoride (or cerium trifluoride), CeF₃, is an ionic compound of the rare earth metal

cerium Cerium is a chemical element; it has Chemical symbol, symbol Ce and atomic number 58. It is a hardness, soft, ductile, and silvery-white metal that tarnishes when exposed to air. Cerium is the second element in the lanthanide series, and while it ...

and

fluorine Fluorine is a chemical element; it has Chemical symbol, symbol F and atomic number 9. It is the lightest halogen and exists at Standard temperature and pressure, standard conditions as pale yellow Diatomic molecule, diatomic gas. Fluorine is extre ...

. It appears as a mineral in the form of fluocerite-(Ce) - a very rare mineral species related mainly to

pegmatites A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than and sometimes greater than . Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic com ...

and rarely to oxidation zones of some polymetallic ore deposits. CeF₃ may be used as a

Faraday rotator A Faraday rotator is a polarization rotator based on the Faraday effect, a magneto-optic effect involving transmission of light through a material when a longitudinal static magnetic field is present. The state of polarization (such as the axis o ...

material in the visible, near-infrared and mid-infrared spectral range.

Structure

The

crystal structure In crystallography, crystal structure is a description of ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that repeat ...

of cerium(III) fluoride is described as the or tysonite structure. It contains 9-coordinate cerium ions that adopt an approximately

tricapped trigonal prismatic In chemistry, the tricapped trigonal prismatic molecular geometry describes the shape of compounds where nine atoms, groups of atoms, or ligand In coordination chemistry, a ligand is an ion or molecule with a functional group that binds to a ...

coordination geometry The coordination geometry of an atom is the geometrical pattern defined by the atoms around the central atom. The term is commonly applied in the field of inorganic chemistry, where diverse structures are observed. The coordination geometry depen ...

, although it can be considered 11-coordinate if two more distant fluorides are considered part of the cerium coordination environment. The three crystallographically independent fluoride ions are 3-coordinate and range in geometry from

trigonal planar In chemistry, trigonal planar is a molecular geometry model with one atom at the center and three atoms at the corners of an equilateral triangle, called peripheral atoms, all in one plane. In an ideal trigonal planar species, all three ligands a ...

pyramidal A pyramid () is a structure whose visible surfaces are triangular in broad outline and converge toward the top, making the appearance roughly a pyramid in the geometric sense. The base of a pyramid can be of any polygon shape, such as triangu ...

References

{{Lanthanide halides Cerium(III) compounds Fluorides Lanthanide halides