Ferroelectric Liquid Crystals

General features of the intrinsic ferroelectric coercive field

“…However, since the discovery of ferroelectricity 80 years ago by Valasek, few published reports have considered the value of the intrinsic coercive field connected with collective polarization reversal, a consequence of the instability of the macroscopic polarization state in an opposing electric field. This is because the measured value of the ferroelectric coercive field was invariably much smaller than the intrinsic value predicted by theory, such as the Landau-Ginzburg (LG) mean-field model [1] and the ferroelectric Ising model [2,3]. The low extrinsic coercive field observed in real ferroelectric crystals and films is caused by nucleation of domains with reversed polarization, which then grow and coalesce by domain wall motion [2,4,5].…”

Dipole glass parameter behaviour for ferro-antiferroelectric solid mixtures

“…Since the unit cell for KDP-type crystal contains two formula units (there are also two sublattices below the phase transition point [29]), the numbers m, m ′ run from 1 to 2. So, we consider the next form for the interactions between all particles in the crystalline lattice: the strict two-particle interaction for particles belonging to the same crystalline lattice site and the self-consistent mean field approximation for particles from different sites, the so-called two-particle cluster approximation [31].…”

The Integration of Two-Dimensional Materials and Ferroelectrics for Device Applications

“…Fundamentally speaking, ferroelectric materials are featured with switchable polarization under an external electric field, which lays the underlying foundation for almost all ferroelectric devices . According to Neumann’s principle, the physical properties of the crystal should be confined to the symmetry feature of the crystal structure . Hence, it is easily concluded that the lack of a center of symmetry is a necessary condition for the existence of the piezoelectric effect in an ideal crystal.…”

“…Among the 20 types of point groups allowing the existence of the piezoelectric effect, there are 10 kinds of point groups that can endow the crystals of these point groups with specific polarization axes . A temperature increase can reduce the electric dipole moment of crystals with these point groups, resulting in changes in the external charge of crystals. , Thus, these crystals are called pyroelectrics. The polarization of some crystals along the polar axis can also be reoriented by an applied electric field, and these crystals are well-known as ferroelectric crystals.…”