Question

Explain Schottky and Frenkel defects.

Answer 1

Schottky defects

1. The Schottky defect is a type of point defect or imperfection in solids that is caused by a vacant position that is generated in a crystal lattice due to the atoms or ions moving out from the interior to the surface of the crystal.
2. This defect is formed when an equal number of cations and anions leave their lattice sites which leads to the creation of vacancies.
3. Generally, the Schottky defect occurs in the crystals having high coordination numbers.
4. Schottky defects decrease the density of crystals by the movement of ions from the lattice.

Frenkel defects

1. A Frenkel defect is another type of point defect which is created when an atom or cation leaves its original place in the lattice structure to create a vacancy while occupying another interstitial position in the crystal.
2. This defect is formed when some ions leave their lattice sites to occupy interstitial sites which leads to the creation of vacancies at lattice sites.
3. Generally, the Frenkel defect occurs in the crystals having low coordination numbers.
4. Frenkel defects do not affect the density of crystals because the overall composition of crystals remains the same.

Therefore, Schottky defects is created by vacant position in the crystal while Frenkel defects leave its original place in the lattice structure.