1. Frenkel Defect + - + - + Cation vacancy - + - + - Interstitial cation
Occurs in ionic solids having smaller cations - + - + -
Frenkel defect is also
called dislocation defect.
For example, ZnS, AgCl, AgBr and AgI due to
small size of Zn2+ and Ag+ ions. + - + - + ds

2. Schottky Defect Number of missing cations and anions are equal + - + -
Cationic Vacancy - + - + -
Anionic Vacancy + - + - +
Schottky defect decreases the density of the substance.
Schottky defect is shown by
ionic substances in which the cation and anion are of almost similar sizes. - + - + - + - + - + ds
For example, NaCl, KCl, CsCl and AgBr.

3. NOTE THAT AgBr EXHIBIT BOTH THESE TYPE OF DEFECTS
COMPARISON
FRENKEL DEFECT
SCHOTTKY DEFECT
BY MISSING OF EQUAL NUMBER OF ANIONS AND CATIONS
BY THE MISPLACEMENT OF CATIONS
DENSITY REMAIN THE SAME
DENSITY DECREASES
OCCURS IN IONIC SOLIDS HAVING SMALLER CATIONS
OCCURS IN IONIC SOLIDS HAVING SIMILAR IONIC SIZE
ELECTRICAL NUETRALITY REMAIN THE SAME BUT THE DIELECTRIC CONSTANT SLIGHTY ALTER
ELECTRICAL NUETRALITY REMAIN THE SAME
STOICHIOMETRIC POINT DEFECT
STOICHIOMETRIC POINT DEFECT
Eg: NaCl,KCl,CsCl,AgBr
Eg: ZnS,AgCl,AgBr,AgI ds
NOTE THAT AgBr EXHIBIT BOTH THESE TYPE OF DEFECTS

4. METAL DEFICIENCY DEFECT
In crystals of FeO some Fe2+ cations are missing and the loss of positive charge is made up by the presence of required number of Fe3+ ions.
Fe2+
Fe2+
Fe2+
Fe3+
O2-
O2-
Fe2+
Fe2+
O2-
O2-
O2-
Fe2+
Fe2+
Fe2+
Fe3+
O2-
O2-
Fe2+
Fe2+
O2-
O2-
O2- ds

5. METAL EXCESS DEFECT DUE TO EXTRA CATIONS
Zinc oxide is white in colour at room temperature. On heating it loses oxygen and turns yellow.
Zn2+
Zn2+
Zn2+
Zn2+
Zn2+
O2-
O2-
O2-
The excess Zn2+ ions move to interstitial sites and the electrons
to neighbouring interstitial sites.
Zn2+
Zn2+
Zn2+
Zn2+
O2-
O2-
O2-
O2-
Zn2+
O2-
Zn2+
Zn2+
Zn2+
O2-
O2-
O2-
Zn2+
O2-
Zn2+
Zn2+
O2-
O2- ds
HEATING

6. F centre- formation- Metal excess defect due to anionic vacancies
Sodium makes NaCl yellow
Potassium makes KCl violet Na
Na+ e-
Lithium makes LiCl pink
Na+
Cl-
Na+
Cl-
F centre-the elctron trapped anion vacancy
Cl-
Na+
Cl-
Na+
Na+
Cl-
Na+
Cl-
Cl-
Na+
Cl-
Na+ ds

7. Introduction of cation vacancy in NaCl by substitution of Na+ by Sr2+
Cation vacancy created by impurity
Cl-
Na+
Cl-
Na+
Cl-
Na+
Na+
Cl-
Na+
Cl-
Na+
Cl- ds

8. Schematic alignment of magnetic moments in (a) ferromagnetic (b) antiferromagnetic and (c) ferrimagnetic.
ferromagnetic
Anti ferromagnetic
ferrimagnetic ds

9. The end
SAJEEVAN
MSHSS
MYNAGAPPALLY ds