Schottky defect

A point defect in an ionic crystal in which vacancies remove cations and anions in proportions that preserve electrical neutrality and overall stoichiometry.

Point defect: A localized disruption of the regular arrangement of atoms or ions in a crystal. Schottky defects are point defects consisting of vacant lattice sites.
Frenkel defect: A point defect in which an ion leaves its lattice site and occupies an interstitial site. Unlike a Schottky defect, it creates a vacancy–interstitial pair without removing ions.
Ionic conductivity: The ability of a material to conduct electric current through the movement of ions. Vacancies provide sites through which ions can migrate in an ionic crystal.
Sodium chloride: An ionic compound composed of sodium and chloride ions in a one-to-one ratio. Its rock-salt lattice can accommodate charge-balanced sodium and chloride vacancies.
Vacancy defect: A crystal defect in which an atom or ion is absent from its usual lattice site. Each missing ion in a Schottky defect creates a vacancy.
Anti-Frenkel defect: A defect in which an anion leaves its lattice site and occupies an interstitial site. It is an anion-based vacancy–interstitial alternative to paired Schottky vacancies.
Diffusion in solids: The movement of atoms or ions through a solid driven by concentration or chemical-potential differences. Ions can diffuse by hopping into vacancies created by Schottky defects.
Cesium chloride: An ionic compound of cesium and chloride ions arranged in the cesium chloride crystal structure. It is a common example used to discuss paired vacancies in ionic lattices.
Ionic crystal: A solid whose lattice is held together primarily by electrostatic attraction between oppositely charged ions. Its alternating charged sublattices allow vacancies to balance one another.
Impurity defect: A crystal defect caused by foreign atoms or ions entering or replacing sites in a lattice. Schottky defects involve missing host ions rather than foreign species.

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