Schottky defect

Schottky defects (also: Schottky disorder ) belong to the lattice defects in crystal lattices. They are point defects in which pairs of voids occur in an ionic lattice. In the simplest case, an ion missing in each Anionenteilgitter and in the cation sublattice. The disorder is named after Walter Schottky. Occasionally, a single space in an ion grid is already being referred to as a Schottky defect.

Description

The Schottky disorder is produced that near-surface ions leave their lattice site, migrate to the surface of the crystal and accumulate there. The resulting vacancy can move through spaces hike in the crystal. They can therefore contribute significantly to the mass transfer and the reactivity of a solid.

Schottky defects are a natural feature of many ionic crystals, that is, they are in chemical equilibrium. They occur mainly in compounds in which a Frenkel disorder is very difficult due to the lack of suitable interstitial sites.

Examples of such crystals, the alkali metal halides such as sodium chloride and potassium chloride. The concentration ( " defect concentration " ) of the vacancies can be formally described by a kind of mass -action law. The number of Schottky defects increases with the temperature because of the entropy is increased ( energy they are unfavorable). The density of Schottky defects in a crystal is proportional to the Boltzmann 's constant, and as a material-specific energy of formation of Schottky defects.