Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals, Vol.357, 167-175, 2001
Ferroelectric polarization hysteresis in a liquid crystal polymer by means of LIMM
We present pyroelectric measurements of the electric field hysteresis in a ferroelectric liquid crystalline polymer. Different electrode arrangements were used to study the pyroelectric response for different directions of the applied electric field with respect to the film geometry and the direction of the incident heat wave. The results demonstrate that in a sandwich cell electrode/foil/FLCP/foil/electrode charge accumulation in the polyester foils leads to a reverse hysteresis loop while conventional hysteresis behavior is observed when the electrodes are in direct contact with the FLCP. In addition we have measured the pyroelectric current in the plane of the film and observed ferroelectric switching and hysteresis in this configuration as well. The LIMM-spectrum shifts significantly toward lower frequencies in this configuration, which is assumed to be mainly due to a heat flow perpendicular to the Laser beam.
Keywords:ferroelectric liquid crystal polymer;spontaneous polarization;pyroelectric measurements;LIMM;hysteresis;bistable switching