Fluorite structure

The fluorite structure is a cubic crystal arrangement in which cations form a face-centered cubic lattice and anions occupy all tetrahedral sites.

Face-centered cubic lattice: A cubic lattice with points at each cube corner and face center. The cations in fluorite occupy this lattice, forming a cubic framework.
Calcium fluoride: The ionic compound CaF₂, commonly known as fluorite or fluorspar. Its crystal structure is the defining example from which the fluorite structure takes its name.
Solid oxide fuel cell: An electrochemical device that converts fuel and oxygen into electricity through reactions at high temperature. Fluorite-related zirconia and ceria ceramics serve as electrolytes or electrode materials.
Rock salt structure: A cubic ionic structure in which each ion has six nearest neighbors of opposite charge. Rock salt has sixfold coordination, unlike fluorite’s eightfold cation and fourfold anion coordination.
Oxygen vacancy: A missing oxygen atom at a site in an oxide crystal lattice. Oxygen vacancies are central to transport and redox behavior in fluorite-related oxides.
Tetrahedral site: A void in a crystal structure surrounded by four atoms at the vertices of a tetrahedron. Fluorite anions fill every tetrahedral void in the cation lattice.
Thorium dioxide: The oxide ThO₂, a refractory ceramic with a high melting point. It adopts the fluorite arrangement with thorium cations and oxide anions.
Oxygen-ion conductivity: The transport of electrical charge through the movement of oxide ions in a material. Oxygen vacancies in doped fluorite oxides provide pathways for oxide-ion transport.
Zinc blende structure: A cubic structure with two interpenetrating face-centered sublattices and fourfold coordination. Both structures use tetrahedral sites, but zinc blende fills only half of them.
Nonstoichiometric compound: A compound whose elemental proportions vary from a simple whole-number ratio. Many fluorite oxides depart from ideal composition as vacancies and changes in oxidation state develop.

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