Question

Which of the following defects in the crystals may lower the density?

• A. Frenkel defect
• B. Schottky defect
• C. All of the above
• D. Interstitial defect

Answer 1

The correct option is B Schottky defect

Interstitial defect :-
This is a crystallographic defect, where additional atoms are present in a normally unoccupied interstial site in the crystal structure. In this case density increases as number of atoms per unit volume increases.

Schottky defect :-
In Schottky defect, pair of one cation and one anion of equal valence is missing from an ionic crystal resulting in formation of pair of vacant sites. These ion–pair vacancies decrease density of the solid.

Frenkel defect :-
In Frenkel defect an ion is displaced from its regular position to
an interstitial position. It does not leave the crystal so density of a solid does not change.