What types of crystals show pyroelectricity ?

Explanation

### Step-by-Step Solution:

1. **Understanding Pyroelectricity**:
- Pyroelectricity refers to the ability of certain materials to generate a temporary voltage when they are heated or cooled. This phenomenon occurs due to the change in temperature, which causes a change in the polarization of the material.

2. **Characteristics of Pyroelectric Crystals**:
- Pyroelectric materials are typically characterized by their natural electrical polarization. This means that they have a permanent dipole moment even in the absence of an external electric field.

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