Question

Explain Schottky defect and Frenkel defect.

Answer 1

Frenkel Defect:-

• A Frenkel defect is another form of a point defect that is created when an atom or a cation leaves its original place in the lattice structure to create a vacancy while occupying another interstitial position within the solid crystal.
• This defect is also known as dislocation defect and this also clearly represents both the vacancy and self-interstitial defects.

• From this figure we can see that the cation has left its own lattice site vacant and it has moved to a new place that is between the cations and anions.

Schottky Defect:-

• This type of defect is formed in the ionic crystals when the oppositely charged ions leave their lattice sites which leads to the creation of the vacancies.
• To maintain a neutral charge in the crystal these vacancies are further created. The figure below further explains that the surrounding atoms also move to occupy these vacancies.
• Normally, when the defect is found in the non-ionic crystals it is referred to as lattice vacancy defect.
• This type of defect can be identified when equal numbers of cations and anions are missing from the lattice.
• It is very much important that an equal number of cations and anions are missing, otherwise, the electrical neutrality of the crystal will not be balanced and thus will get affected.