Dielectric relaxation spectroscopy of a nematic liquid crystal doped with ferroelectric Sn 2 P 2 S 6 nanoparticles

Abstract

To cite this article: E. Ouskova , O. Buchnev , V. Reshetnyak , Yu. Reznikov & H. Kresse (2003) Dielectric relaxation spectroscopy of a nematic liquid crystal doped with ferroelectric Sn 2 P 2 S 6 nanoparticles, Liquid Crystals, 30:10, It was found that doping a nematic liquid crystal (LC) with a small amount of ferroelectric nanoparticles strongly affects the dielectric properties of the system. In particular, adding the ferroelectric particles results in a shift of the absorption bands corresponding to the rotation of liquid crystal molecules around their short axes to lower frequencies and in an increase of the amplitude and with of the absorption bands. This suggests that strong interactions occur between the LC molecules and the particles, caused by the large dipole moment and high polarizability of the ferro-particles. The ferroelectric particles affect not only dielectric losses, but also dielectric permittivity of the system. Specifically, the static dielectric permittivity and the dielectric anisotropy of the suspension are more than twice that of the pure LC.

Maier-Saupe-type theory of ferroelectric nanoparticles in nematic liquid crystals

“…One particularly interesting case occurs if the particles are ferroelectric. Experiments have shown that low concentrations of ferroelectric Sn 2 P 2 S 6 or BaTiO 3 nanoparticles increase the orientational order parameter, increase the isotropic-nematic transition temperature, and decrease the switching voltage for the Frederiks transition [7][8][9][10][11][12][13][14]. Thus, they provide a new opportunity to enhance the properties of liquid crystals for technological applications.…”

Effect of nanoparticle chain formation on dielectric anisotropy of nematic composites

“…Thus one can readily see (compare also with Figs. 3a and 3b) that the experimentally observed increase of the dielectric constant [9,13] at very low NP number density ρ = 10 −2 − 10 −3 can be explained by the effect of chain formation only if the dipole-dipole interaction strength is sufficiently high which is the case for ferroelectric NPs with large spontaneous polarization.…”

“…Strongly anisotropic interaction between NPs, including, in particular, the dipole-dipole one, will lead to the formation of polar chains. It has been shown [13] that the equilibrium chain length strongly depends on the contact interaction potential normalized by the temperature. Long chains of NPs may occur only if the contact interaction is of the order of 10k B T [15] which is satisfied, for example, for ferroelectric NPs [9,13].…”

“…It has been shown [13] that the equilibrium chain length strongly depends on the contact interaction potential normalized by the temperature. Long chains of NPs may occur only if the contact interaction is of the order of 10k B T [15] which is satisfied, for example, for ferroelectric NPs [9,13]. Such long polar chains should make a significant contribution to the dielectric anisotropy of nematic composites.…”

Effect of magnetic nanoparticles on the nematic-smectic-A phase transition

“…carbon nanotubes, silica microbeads, nanoparticles and various collides exhibit remarkable new physical phenomena. Experiments have shown that nanoparticles and ferroelectric nanoparticles can greatly enhance the physical properties of nematic and smectic liquid crystals [1][2][3][4][5][6][7][8][9][10][11].…”