Pyroelectric properties of liquid crystals

Abstract

Abstract Possibilities are discussed of observing the pyroelectric effect in ferroelectric and nonferroelectric (under special conditions) liquid crystals. The temperature dependencies of the volume pyroelectric coefficient γ(T) and spontaneous polarization P(T) are demonstrated for the chiral smectic C* and H* phases. The relationship between the P value and the location of an electric dipolar moment in a molecule of the liquid crystals has been established. The dynamics of the spontaneous polarization have been investigated and the critical decrease of P detected near the smectic C* ↔ smectic H* and smectic C* ↔ smectic A phase transitions. The effect of impurities, particularly conductive ones, on pyroelectric properties and polarization of liquid crystals is discussed in detail. For the first time non-helicoidal liquid crystalline ferroelectrics have been prepared using certain mixtures of left- and right-hand rotating chiral smectic phases. High values of the spontaneous polarization have been detected in tilted smectic phases with ferroelectricity induced by chiral impurities.