Interstitial Defect:
A crystal in which some constituent particles occupy an interstitial site, are said to have interstitial defect which increases the density of the substance.
Ionic solids exhibit their defects as Frenkel and Schottky defects. Frenkel Defect:
o
o
This defect is exhibited by the ionic substances due to the large difference in size of ions.
The smaller ion( cation) is displaced from its normal site to an interstitial site which creates a vacancy defect at its original site and an interstitial defect at the new location.
o It is also called dislocation defect. o It does not alter the density of the solid.
o
For example, ZnS, AgCl, AgBr and AgI due to small size of Zn2 + and Ag + ions.