BaTiO 3 ferroelectric nanoparticles dispersed in 5CB nematic liquid crystal: Synthesis and electro-optical characterization

Abstract

We report in this paper studies on a mixture of nematic liquid crystal (5CB) and BaTiO3 ferroelectric nanoparticles (NPs). Apart a drastic change in the electro-optical (EO) properties of this mixture, which is reported as a conclusion, we focused our attention onto the characteristics of those NPs. The initial powder obtained by solid way is first analyzed: this material is crystallized in the ferroelectric phase as shown by x-ray diffraction and Raman spectroscopy. A high speed second milling was performed to obtain NPs: they have been characterized by high resolution transmission electron microscopy (size and structural characterizations) and by dynamic light scattering. Then these NPs were blended with a nematic liquid crystal (5CB). Raman spectroscopy measurements were used to measure and compare the scalar order parameter of both samples. The EO properties were measured in planar liquid crystal cell configuration by using classical EO setup. We amazingly found a significant decrease in the Freedericksz threshold, compared to the pure material. This is to be compared to the Glushchenko’s measurement, who observed no variation, for a similar mixture in concentration, but for smaller NPs. Switching times were measured using the same setup and we noticed a decrease in the “τon” for the 5CB+BTO mixture compared to the pure 5CB one.