Explain the following terms with suitable example:
a. Schottky defect b. Frenkel defect
c. Interstitials d. F-centres

Explanation

(i) A Schottky defect - When equal no of cations and anions are missing form lattice of ionic crystal.
(ii) Frenkel defect - When an ion is missing from lattice occupy the interstitial site to maintain the electrical neutrality.
(iii) F-centre - A negative ion miss from its site, leave the hole which is occupied by an electron which is called F-centre.