Harvesting single ferroelectric domain stressed nanoparticles for optical and ferroic applications

Abstract

We describe techniques to selectively harvest single ferroelectric domain nanoparticles of BaTiO3 as small as 9 nm from a plethora of nanoparticles produced by mechanical grinding. High resolution transmission electron microscopy imaging shows the unidomain atomic structure of the nanoparticles and reveals compressive and tensile surface strains which are attributed to the preservation of ferroelectric behavior in these particles. We demonstrate the positive benefits of using harvested nanoparticles in disparate liquid crystal systems.

The influence of suspended nanoparticles on the Frederiks threshold of the nematic host

“…In our results, the tetragonal peak has disappeared on milling and there is no shift. Cook et al [12] have identified strain in the particles as an important factor for maintaining the ferroelectric phase, but it remains unclear why our, apparently very similar, procedure does not produce a significant amount of strained on May 10, 2018 http://rsta.royalsocietypublishing.org/ Downloaded from…”

“…Even though the harvesting procedure described in Cook et al [12] was not applied, some confirmation that milled BaTiO 3 retains the tetragonal phase was expected especially because a downwards shift of the Frederiks transition for BaTiO 3 suspensions was reported in Blach et al [4] and Cook et al [12] for milled particles. We tried to mill under equivalent conditions as described in Atkuri et al [5], but failed to generate samples that showed any characteristic indicative of ferroelectricity.…”

“…Comparing our results for milled BaTiO 3 in 5CB with those reported in Blach et al [4], we conclude that the precise details of the milling process are significant in preserving some ferroelectricity in particles that are small enough to suspend. Indeed, in Cook et al [12], it was already noted that there was a large variability between batches milled in the same way. In Blach et al [4], the tetragonal peak is present in the Raman scattering from milled BaTiO 3 and a shift in the Frederiks transition was observed in 5CB suspension.…”

Terahertz properties of liquid crystals doped with ferroelectric BaTiO3 nanoparticles

“…Additionally, the synthesis of a material with desired physical properties typically requires to use of more than ten components; the more components are included, the more difficult it is to predict final material properties. The ferroelectric nanoparticles can improve the LC materials properties without chemical synthesis and the properties can be varied by changing the type and the amount of nanoparticles mixed with LC [2,7,8]. The improved properties of liquid crystals doped with ferroelectric nps are likely to be caused by a strong dipole-dipole interaction between the ferroelectric nanoparticles and the surrounding liquid crystal molecules.…”

Doping the nematic liquid crystal 5CB with milled BaTiO3nanoparticles

“…Nanoparticles of 9 nm in average diameter suspended in heptane were obtained by milling for 25 h [12,13]. Stressed BaTiO 3 nanoparticles, which possess permanent electric polarization, can be extracted from such dispersions by harvesting [14].…”