Fluorittstrukturen

Fluorittstrukturen, or fluorite structures, describe a crystal-structure type in which cations form a face-centered cubic (fcc) lattice and anions occupy all tetrahedral holes. The prototypical composition is AB2, as in calcium fluoride CaF2. In CaF2, Ca2+ ions occupy the fcc lattice points, while F− ions fill the tetrahedral interstices. The result is a cubic crystal with space group Fm3m. Each Ca2+ is coordinated by eight F−, and each F− is coordinated by four Ca2+.

This structure occurs in many compounds beyond CaF2, notably oxides such as CeO2 (ceria), UO2, ThO2, and PuO2, where the oxide ions form the fluorite-like sublattice and the cations occupy the lattice points. In these materials, the overall arrangement remains cubic and the same coordination pattern—eightfold for the cations, fourfold for the anions—often applies. The oxide fluorite-type is common in ceramic and nuclear materials.

Doping fluorite-structured oxides with vacancies or aliovalent dopants leads to oxide ion conductors, including stabilized zirconia (YSZ) and doped ceria (GDC). These materials exhibit high ionic mobility and are widely used as solid electrolytes in solid oxide fuel cells, sensors, and related devices. The fluorite framework thus provides a simple, highly symmetric basis for a family of ionic solids with diverse chemical compositions and functional properties.

Fluorittstrukturen serve as a fundamental reference in crystallography and solid-state chemistry, and they form the basis for several related structure types and defects that influence material behavior.