Characteristic switching and dielectric parameters of ferro- and anti-ferroelectric phases of (S)-(+)-(1-methylheptyloxycarbonyl) phenyl 4′-(6-perfluoropentanoyloxyhex-1-oxy) biphenyl-4-carboxylate

Abstract

We have studied spontaneous polarization, switching time and dielectric parameters (namely dielectric strength, relaxation frequency, distribution parameter) of a 5 µm thick planar oriented sample of a highly tilted anti-ferroelectric liquid crystal material (S)-(+)-(1-methylheptyloxycarbonyl) phenyl 4′-(6-perfluoropentanoyloxyhex-1-oxy) biphenyl-4-carboxylate. The spontaneous polarization is found to increase with decreasing temperature. It follows power law Ps = P0(1 − (T/Tc))γ with γ = 0.46 ± 0.01. The maximum value of Ps is found to be 224 nC cm−2 near room temperature. The impedance spectroscopy of the material has been carried out in the frequency range 1 Hz–35 MHz. The soft and Goldstone modes of dielectric relaxations have been detected in the paraelectric SmA* and the ferroelectric SmC* phases, respectively. Two absorption modes are observed in the anti-ferroeletric phase due to anti-ferroelectric ordering of the molecules, each of which is separated by about two decades of frequency.