difference between Schottky and Frenkel defects
A type of point defect in which equal numbers of cations and anions are missing from their lattice sites.A defect in which an ion (usually a cation) leaves its normal lattice site and occupies an interstitial site.
| Type of Vacancy | vacancies in the crystal lattice. | Creates a vacancy and an interstitial defect simultaneously. |
| Effect on Density | Decreases density of the crystal (since some ions are missing). | No change in density, because the total number of ions remains the same. |
| Common in | Ionic compounds with similar-sized cations and anions, e.g. NaCl, KCl, CsCl, AgBr. | Ionic compounds with large difference in ion sizes, e.g. ZnS, AgCl, AgBr, AgI. |
| Electrical Neutrality | Maintained because equal number of positive and negative ions are missing. | Maintained because the displaced ion remains within the crystal. |
| Occurs at | High temperatures in crystals with high coordination numbers. | Crystals with low coordination numbers and large size difference between ions. |
| Na⁺ + Cl⁻ (both missing) | Na⁺ moves from lattice site → interstitial site |