Electric Response of a Negative Dielectric Anisotropy Nematic Liquid Crystal Doped with Ionic Dopant

Abstract

The electrical properties measurements have been performed in a homogeneous alignment parallelepiped cell containing 4-methoxy benzylidene- 4-butylaniline (MBBA) liquid crystal doped with 0.02%wt tetrabutylammonium bromide (TBAB). The measurement of the complex permittivity was conducted in the nematic phase, covering a frequency range of 42 Hz to 5 MHz. A new relaxation mode was observed in the low-frequency region, which was not present in pure MBBA. The obtained dielectric dispersion could be fitted using the double Cole–Cole formula to determine the relaxation frequencies. The steady-state current exhibited a nonlinear dependence on the applied voltage, and hysteresis was observed in the transient current-voltage characteristic curve.