Question

Define : Schottky defect

Hint:

Remember: Schottky = "Shot" (missing) ions. Since ions are literally gone from the lattice, the mass decreases while volume stays same, so density drops.

Answer 1

Step 1: Understanding the Concept:
In an ideal crystal, every lattice site is occupied by the designated ion. Real crystals have defects. Schottky defect is a stoichiometric "vacancy" defect.
Step 2: Detailed Explanation:
In ionic solids, electrical neutrality must be maintained. Therefore, if a cation is missing from its site, an anion must also be missing.
Characteristics:
1. It occurs in ionic compounds where the coordination number is high.
2. It is seen in compounds where cations and anions are of similar sizes (e.g., \( NaCl, KCl, CsCl \)).
3. Because atoms are missing from the crystal, the density of the substance decreases.
Step 3: Final Answer:
A Schottky defect is a vacancy defect in ionic solids created by missing pairs of oppositely charged ions, leading to a decrease in density.