Peculiarities of electro-optic properties of the ferroelectric particles-liquid crystal colloids

Abstract

Influence of ferroelectric barium titanate particles on electro-optic properties of the liquid crystal (LC) 4-cyano-4′-pentylbiphenyl (5CB) with positive dielectric anisotropy and the LC mixture (H37) consisting of 4-methoxybezylidene-4’–butylaniline and 4-ethoxybezylidene-4’–butylaniline with negative dielectric anisotropy was investigated. It was shown that a presence of particles (1 wt%) in 5CB and H37 decreased the clearing temperature from 35.2 °C to 32.4°C and from 61.2°C to 60.1°C, respectively. The threshold voltage of the Freedericksz effect became 0.3 V for the BaTiO3-5CB colloid while the beginning of this effect for the pure 5CB was observed at 2.1 V. The threshold voltage of the Freedericksz effect increased from 2.8 V to up 3.1 V at additive of particles in H37. A rise time of the BaTiO3-5CB colloid improved while a decay time worsened in comparison with the pure 5CB at all applied voltages. The inverse trends were observed for the H37 matrix, namely, a rise time worsened and a decay time improved. Among other things, the pecularities of Williams’ domain formation (WDF) were also investigated in the colloid based on the H37 matrix. It was established that the WDF voltage decreased, a rise time increased and a decay time decreased in comparison with the pure H37. Experimental results are explained by appearance of local electric fields near the polarized ferroelectric particles at application of external electric field and an existence of the additional obstacles (particles) for movement of ions.