Fluoritetype

Fluorite-type refers to a crystal structure type and to minerals and compounds that crystallize in a fluorite-like arrangement. In this structure, the larger cations form a face-centered cubic lattice, and the smaller anions occupy all the tetrahedral holes, resulting in the formula AX2. The ideal coordination is eight-fold for the cation and four-fold for the anion, and the structure has cubic symmetry (space group Fm-3m).

Common examples include CaF2 (the mineral fluorite) and several oxide fluorite-type materials such as CeO2, UO2, ThO2, and stabilized zirconia (for example Y2O3-stabilized ZrO2). These compounds share high symmetry and a robust anion sublattice, which supports ionic transport when defects or dopants are present.

Properties: The fluorite-type arrangement affords variable stoichiometry and defect chemistry, enabling high ionic conductivity in doped oxides, and it normally shows isotropic properties in the ideal case.

Applications and significance: The term is widely used in crystallography and materials science to classify compounds that crystallize in this arrangement, including many fuel-cell electrolytes and ceramics. The mineral fluorite (CaF2) is also valued in geology and industry as an ore and as a decorative mineral.