Question

_______ occurs when a foreign substance replaces an atom in a crystal.

(a) Vacancy defect

(b) Substitutional impurity

(c) Frankel defect

(d) Interstitial impurity

The question was asked by my college director while I was bunking the class.

The doubt is from Crystal Defects topic in section Imperfection in Metal Crystals, Fracture, Corrosion and Oxidation of Engineering Material & Metallurgy

Answer 1

Correct option is (b) Substitutional impurity

To explain I would say: A substitutional impurity occurs due to the occupation of a foreign atom in place of an atom in a crystal. On the other hand, interstitial impurities occur when a regular atom occupies a random space in the crystal lattice.