Dielectric studies of different phases of a thin-layered ferroelectric liquid crystal with a small pitch and high spontaneous polarization

Abstract

Dielectric spectroscopy of a ferroelectric liquid crystal with planar texture in the frequency range 100 Hz to 1 MHz has been carried out as a function of temperature from 25°C to 60°C at different DC fields varying from 0 to 12 kVcm⁻¹. From the measured dielectric strengths and relaxation frequencies, it is observed that the material has a S_c∗-S_A∗ transition at 56·1°C and a S_A∗-I transition at 58°C. The data of the S_c∗ phase have been assigned to the Goldstone mode. The rotational viscosity and elastic constant have been calculated from the observed data. The capacitance shows an abrupt drop at the critical DC field where unwinding of the helix occurs. The measured value of the critical field decreases with temperature and agrees to literature data from electrooptical experiments. On applying a DC field greater than 6·5 kV cm⁻¹ at room temperature, the liquid crystal shows the unwound S_c∗ and S_A∗ phases.