Choose the graph that best describes the variation of dielectric constant r with temperature T in a ferroelectric material. T C is the Curie temperature.

GATE 2021 PH – Question 11

Solid State Physics · Polarizability, ferroelectricity · 1 mark · Multiple choice

Choose the graph that best describes the variation of dielectric constant $\epsilon_r$ with temperature $T$ in a ferroelectric material. $T_C$ is the Curie temperature.

Figure (A)
Figure (B)
Figure (C)
Figure (D)

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Correct answer: (A) Figure (A)

Explanation

The dielectric response becomes very large near the ferroelectric transition. Above $T_C$, the Curie–Weiss law gives $\epsilon_r\propto1/(T-T_C)$, so the dielectric constant decreases as the temperature moves away from the transition. Below $T_C$ it rises toward the transition. The peak at $T_C$ and decay on either side correspond to A.