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Question
Write the consequences of Schottky defect with reasons.
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Solution
Consequences of Schottky defects are:
- As the number of ions decreases, mass decreases. However, volume remains unchanged. Hence, the density of a substance decreases.
- The number of missing cations and anions is equal, and the electrical neutrality of the compound is preserved.
- This defect is found in ionic crystals such as NaCl, AgBr and KCl.
- Since some ions are missing from the crystal lattice, the mass of the crystal decreases without a corresponding change in volume.
- The overall density of the crystal decreases.
- Equal numbers of positive and negative ions are missing, so there is no net charge.
- The electrical neutrality of the crystal is preserved.
- The ratio of cations to anions remains the same because equal numbers are missing.
- The chemical formula of the compound remains unchanged.
- The presence of vacant sites may allow ions to move slightly under an electric field.
- There is a small increase in ionic conductivity, especially at higher temperatures.
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