Question

The common point defect(s) in a solid is/are

• A. Wadsley defect
• B. Schottky defect
• C. Suzuki defect
• D. Frenkel defect

Answer 1

The Correct Option is B, D

In solids, point defects refer to the imperfections found at a single or minimal number of sites in the crystal structure. The two common types of point defects in solids are 'Schottky defect' and 'Frenkel defect'. Let's discuss these defects:

1. Schottky Defect:
   • This defect occurs when equal numbers of cations and anions are missing from the crystal lattice to maintain electrical neutrality.
   • It is common in ionic compounds with a high coordination number and similarly sized anions and cations, like NaCl and KCl.
   • The defect results in a decrease in the density of the substance.
2. Frenkel Defect:
   • This defect occurs when a cation leaves its lattice site and occupies an interstitial position, creating a vacancy and an interstitial defect simultaneously.
   • It is more common in ionic compounds with a large difference in sizes of cation and anion, such as ZnS and AgCl.
   • Frenkel defect does not change the density of solids as ions do not leave the solid.

Other Given Options:

• Wadsley Defect: This is not commonly classified as a point defect. Wadsley defects often relate to non-stoichiometry and structural changes in the solid rather than specific point defects.
• Suzuki Defect: Typically associated with dislocations and not considered a point defect in the same manner as Schottky or Frenkel defects.

Hence, the correct point defects found in solids are the 'Schottky defect' and 'Frenkel defect'.