Question

Which of the following statement(s) is/are incorrect regarding the defects in solids?

• A. $AgBr$ crystal show both Schottky and Frenkel defect
  
• B. Solids containing F-centers are paramagnetic
  
• C. Doping in crystal introduces dislocation defect
  
• D. Metal deficient defect can occur with extra cation present in the interstitial voids

Answer 1

Answer: (C), (D)

Metal deficient defect can occur with extra cation present in the interstitial voids

$AgBr$ shows both, Frenkel as well as Schottky defects.
Thus, statement (a) is correct.

F-centers are vacant site of crystal lattice, which is occupied by electrons and can show color after excitation. Solids containing F-centers are paramagnetic, as the electrons occupying the vacant sites are unpaired.
Thus, statement (b) is correct.

Doping a different valency metal may either result in a free electron or positive hole. It does not make ions to move away from their lattice sites and occupy interstitial positions
So, statement (c) is an incorrect.

Some solids contain less amount of metal as compared to the stoichiometric proportion. These shows metal deficiency defect.
Example:
$FeO$ is found, mostly, with a composition of $F{e}_{0.95}O$. Here, loss of some $F{e}^{2+}$ ions is compensated by presence of required number of $F{e}^{3+}$ ions