Characteristic of Dielectric Behaviour of Ferroelectric Liquid Crystal at Smectic-A and Chiral Smectic-C Phase Transition

Abstract

A sharp peak of dielectric constant which appears at the phase transition between chiral smectic-C and smectic-A phases is found to become clear under dc bias field and in thin cells in which the Goldstone mode originated from the fluctuation of azimuthal angle of molecular long axis corresponding to the winding and unwinding motions of helix characteristic to ferroelectric liquid crystal is suppressed.
The temperature T_m where dielectric constant shows maximum is found to increase under dc bias field E corresponding to the field induced ferroelectric phase at higher temperature than T₀ (Curie temperature under no bias field) with the relation of (T_m−T₀)∝E^2⁄3. The peak dielectric constant ε_p is also found to be suppressed with the dc bias field with the relation of ε_p∝E^−2⁄3. The results clearly support that the phase transition of these compounds is of the second order.