What are stoichiometric defects in ionic solids ? Explain.

Explanation

Schottky defect `:`
(i) Schottky defect arises due to the mission of equal number of cations and anions from the crystal lattice.
(ii) This effect does no change the stoichiometry of the crystal.
(iii) Ionic solids in which the cation and anion are of almost of similar size show schottky defect . Ex `:` NaCl.
(iv) Presence of large number of schottky defects in a crystal, lower its density.

Frenkel defect `:`
(i) Frenkel defect arises due to the dislocation of ions from its crystal lattice.
(ii) The ion which is missing from the lattice point occupies an interstitial position.
(iii) This defect is shown by ionic solides in which cation and anion differ in size.
(iv) Unlike Schottky defect, this defect does no affect the density of the crystal .
(v) For example AgBr, in this case, small `Ag^(+)` ion leaves its normal site and occupies an interstitial position.