Dielectric Relaxation Behavior and Thickness Dependent Phase Transition of a Ferroelectric Liquid Crystal

Abstract

Dielectric relaxation behavior of a ferroelectric liquid crystal (Felix-15/100) showing SmC*–SmA phase transition have been reported. Thickness dependent dielectric constant measured by varying the cell thickness (∼6, 11, 18, 36, 59 and 79 µm) showed increase of dielectric constant and the ferroelectric transition (Curie temperature TC) with increase of cell thickness. The observed non-linear variation of TC as a function of thickness is better described by an empirical formula of the form Tx=TC-γd-β (where β and γ are sample dependent parameters). Since d is related to the domain width, different values of β and γ are related to the domain width and hence with the dipolar ordering. Different values of the sample dependent parameters β and γ may, therefore, be considered as a measure of molecular ordering (depending on molecular interaction) which causes the change of TC with thickness. It is thus concluded that the values of β and γ should be related to the dipolar interaction in the ferroelectric system under consideration.