Question

Dopping of $AgCl$ crystal with $CdC{l}_2$ results in:

• A. Schottky defect
• B. Frenkel defect
• C. Impurity defect
• D. Formation of F-centers

Answer 1

The correct option is C Impurity defect

Silver is monovalent while cadmium is divalent. Their ionic sizes do not differ much since being neighbours.
When $AgCl$ is dopped with $CdC{l}_2$ to balance the charge difference each doubly charged $C{d}^{2+}$ ion has to displace two silver monovalent ions from two cationic sites. When cadmium ions substitutes silver ions, only one of the two vacant silver ion sites will be substituted by cadmium ion and the other will remain vacant.
So, the dopping of $AgCl$ crystals with $CdC{l}_2$ results in the creation of impurity defect.