Question

Explain Schottky and Frenkel defects.

Answer 1

a) Schottky Defects ;
This detect is caused if sonic of the lattice-points are unoccupied. The points which are unoccupied are called lattice vacancies. The number of missing positive end negative ions is, the same in this case and the crystal remains neutral. The existence of two vacancies, one due to a missing $N^{+}$ ion and the other due to a missing $C{r}^{-}$ ion in a crystal of NaCl. It appears ionic crystals in which be positive and negative ions do not differ much in, size.
b) Frenkel defect:
This defect arise when an ion occupies interstitial position beteen the lattiec points.
This This defect occurs generally in ionic crystals in which much larger in size than the cation.
AgB is example for type of defect one of the Ag ion occupies a position in the interstilial space rather than its own appropriate site in the lattice.
The crystal remains neutral since the number of positive ions is the same as the number of negative ions.