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

cerium Cerium is a chemical element with the symbol Ce and atomic number 58. Cerium is a soft, ductile, and silvery-white metal that tarnishes when exposed to air. Cerium is the second element in the lanthanide series, and while it often shows the +3 ...

and fluorine. 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 co ...

and rarely to oxidation zones of some

polymetallic In chemistry or mining, polymetal or polymetallic is a substance composed of a combination of different metals. When the substance contains only two metals the term '' bimetal'' (''bimetallic'') is sometimes preferred. A (or ') is an ore that ...

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 the ordered arrangement of atoms, ions or molecules in a crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric patterns ...

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

coordination geometry The term coordination geometry is used in a number of related fields of chemistry and solid state chemistry/physics. Molecules The coordination geometry of an atom is the geometrical pattern formed by atoms around the central atom. Inorganic coo ...

, 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 to

pyramidal A pyramid (from el, πυραμίς ') is a structure whose outer surfaces are triangular and converge to a single step at the top, making the shape roughly a pyramid in the geometric sense. The base of a pyramid can be trilateral, quadrilater ...

References

Cerium(III) compounds Fluorides Lanthanide halides {{inorganic-compound-stub