Question

Explain with a diagram the Frenkel defect.

Describe the Frenkel defect found in ionic crystals.

Explain the following term with suitable examples:

Frenkel defect

Answer 1

1. A Frenkel defect happens when an ion in an ionic compound is absent from its usual spot in the lattice and instead sits in a space between the lattice points.
2. The cations are usually smaller than anions. Therefore, the cations occupy interstitial sites. The smaller cation shifts from its usual location to the interstitial space.
3. It, therefore, creates a vacancy defect at its original position and an interstitial defect at its new location in the same crystal.
4. A Frenkel defect can be regarded as the combination of a vacancy defect and an interstitial defect. 
5. In alkali metal halides, Frenkel flaws don't happen very often because the alkali metal cations are too big to fit into smaller spaces between the atoms.
6. Frenkel defects are common in silver halides, e.g., AgCl, AgBr,  CaF₂ and Agl. They are also found in ZnS crystal.