Imperfection or defects in solids : Any deviation from perfectly ordered arrangement of constituent particles in crystalline solids.
Types of defects:
1. Point defects : Any deviation around a point in solids.
2. Line defects : Any deviation along row in solids.
Types of point defects
(A) Stoichiometric defects : Defects in which the stoichiometry of compound is not distrubed.
eg. 100 formula units of NaCl present in crystal ,means 100 Na+ ions and 100 Cl- ions present in crystal and stoichiometric ratio is 1:1, if out of 100 , 5 formula units missing from their lattice site and 95 formula units left, even than ratio between Na+ and Cl- ion is 1:1
Stoichiometric defects in non ionic compound :
1.Vacancy defects: When some some lattice points are vacant in crystal lattice.
Effect : Density of crystal decreases.
2. Interstitial defects: When constituent particles occupy the interstitial sites in crystal lattice.
Effect : Density of crystal increases.
Stoichiometric defects in ionic compound :
1. Schottky defects: When equal numbers of cation and anions are missing from their lattice site in crystal lattice.
Effect : Density of crystal decreases.
2.Frankel defects :When cation (usually) leave their lattice site and occupy the interstitial site in crystal lattice.
Effect : No effect on density of crystal.
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