Schottky defect causes

Options

A. Increase in the density of solid
B. Decrease in the density of solid
C. No change in the density of solid
D. Decrease in the conductivity of solid.

Answer

### Step-by-Step Solution:

1. **Understanding Schottky Defect**:
- The Schottky defect occurs in ionic crystals when there is a complete absence of some cations and anions from their lattice positions. This results in vacancies in the crystal structure.

2. **Effect on Density**:
- Density is defined as mass per unit volume (Density = Mass/Volume).
- In the case of Schottky defect, since some ions (both cations and anions) are missing, the total mass of the crystal decreases.
- As the mass decreases while the volume remains constant, the density of the solid will decrease.

3. **Effect on Conductivity**:
- Conductivity in ionic solids is largely due to the movement of ions.
- The presence of vacancies (due to Schottky defects) can facilitate the movement of ions, potentially increasing the conductivity.
- Therefore, while the density decreases, the conductivity may actually increase due to the presence of these defects.

4. **Conclusion**:
- Based on the effects of Schottky defect, the correct answer to the question is that it causes a decrease in the density of the solid.

### Final Answer:
- **Decrease in the density of the solid**.

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