Electric-Field-Induced Reorientation Of Ferroelectric Micro- And Nano-Platelets In The Nematic Liquid Crystal

We demonstrate that ferroelectric layered perovskite Bi(3.8)Nd(0.2)Ti(3)O(12)micro-platelets can be reoriented in the nematic liquid crystal by the linear coupling to an external electric field. The electric dipole moment of platelets is perpendicular to the plane of platelets and provides torque that rotates the platelets. The experiments were made in dispersions of ferroelectric platelets in a zero dielectric anisotropy nematic liquid crystal (LC), which excludes the reorientation of the dispersion via the dielectric coupling of a LC. Typical reorientation times for micrometre-size ferroelectric platelets are of the order of 100 ms for 0.5 V/mu m applied electric field. The electric dipole moment in the absence of external field is very small and does not contribute to the force between the platelets. This could be either due to very narrow hysteresis loop of the ferroelectric material, or screening of dipolar electric field by ions in the LC. A stable and homogenous dispersion of ferroelectric nano-platelets could not be observed in any range of platelets' concentration. To create a ferroelectric LC the shape and thickness of the nano-platelets has to be controlled, and the electrostatic screening of dipolar field should be minimised.