B. M. Darinskii

APPEARANCE OF INTERNAL BIAS FIELD IN FERROELECTRIC GROWTH PROCESS

Abstract The growth regularities of the internal bias field Eb formation have been investigated in pure triglycine sulphate crystals, as well as in crystals doped with chromium or α-alanine. All crystals were grown in the ferrophase from the seed of the pivot form oriented by its axis along the non-polar crystal axis Z. It was found that the bias field had different signs in the samples lying on opposite sides of the seed along the polar axis Y in the crystals with chromium impurity and pure crystals and the same sign in α-alanine doped ones. The probable mechanism of Eb field formation is suggested for both cases.

The motion of the domain boundaries in crystals of KH2PO4 group

Abstract The lateral motion of 180-degree domain walls in ferroelectrics is considered. The motion is realized by the thermofluctuational nucleation and subsequent spreading of the reverse domain nucleuses on the domain wall. The energy and the velocity of the lateral walls of nucleus for different orientations, energies and dimensions of the critical nucleus are determined. Different avelocity regimes of the lateral motion of domain wall are analysed. The results of general analysis are applied to the case of strong temperature dependence of the barrier height in periodic potential relief of the domain walls, connected to co-ordinate dependence of the walls energy. Strong dependence on the temperature of mobility of the domain boundaries, obtained here, explains the pnenomenon of domain structure “freezing” in crystals of KH2PO4 group, The dependence of the “freezing” temperature on the amplitude of the measuring field is calculated.

Internal field in ferroelectric films with different electrodes

It has been shown that a difference between the binding energies of electrons in different electrodes induces an electric field in the bulk of a ferroelectric film, which can be interpreted as a kind of internal bias field. The values of the internal bias field in films of different thicknesses have been found and compared with the theoretical calculations.

Exoelectron emission from ferroelectric surface in alternating electric field

Abstract An electron emission in TGS crystal stimulated by the switching in pulsed external electric field is studied. A presence of critical (for the emission beginning) value of the field, decreasing with the growth of temperature, is shown. Obtained results are described in frames of mechanism connected with formation of the electric field concentrators at the places of the domain boundaries fixing by the surface imperfection.

The structure and the motion of the domain boundaries of ferroelectrics—ferroelastics

Abstract The effective width of the domain wall in ferroelectric—ferroelastic crystals having imperfections of different types interacting with domain wall is determined. Contribution of the domain boundaries to the dielectric permittivity and elastic compliance of examined crystals is determined taking into account of the initially deformed profile of the domain walls in real crystals.

Non-Linear Waves in Ferroelastics

Theoretical investigation of nonlinear periodical waves in ferroelastic crystals is made. The conditions of appreciable effect of media nonlinearity on wave characteristics are found. Analytical expressions for dependences of wave velocity on the wave length and oscillation amplitude are derived. It is shown that in the crystals soliton-like excitations can exist and characteristics of the solitons are found.

Formation of the domain structure by the cooling of ferroelectric surface

Abstract The paper is devoted to formation of the domain structure according to the mechanism of loss of stability in ferroelectric with phase transition of the second order in presence of the temperature gradient δT/δz directed into the volume of deposit. It is determined that the domain structure becomes smaller by the growth of the temperature gradient. The expression for the value of the deposit surface over-cooling ΔT, by which the mentioned domain structure appears, is obtained.

Domain Walls Creep in Thin Ferroelectric Films

The switching processes in lead titanate thin films in subcritical rectangular pulsed fields have been investigated. Based on the obtained results, the dynamic exponent factor in the dependence of the domain wall velocity on the value of external field has been evaluated. It was shown that the value of the exponent factor increases as the film thickness decreases. The growth of the dynamic factor is associated with an increase in the crystallite axes orientation, when the thickness of polycrystalline films decreases.

Phase transitions in crystals characterized by polarization and deformation components of the order parameter

Abstract By the method of Landau thermodynamics a possibility of realization of phase transitions characterized by a vector of polarization and a tensor of deformation in crystals of all classes of point group of symmetry is investigated. The analysis is carried out by drawing up of the lists of invariants, constructed from a component of the order parameter. It is shown, that such phase transitions are possible in 14 crystallographic classes. The orientations of domain boundaries in low symmetrical phases and nonlinear effects are specified

Effective dielectric constant of the polydomain ferroelectric plate

ABSTRACT The static dielectric response to an external electric field is calculated for a ferroelectric plate with a plane-parallel domain structure. The case of the free not fixed by defects domain boundaries was investigated. It is assumed that domain boundaries under external field will bend in the surface region so as to fully compensate an external field by the field of bound charges at the bent boundary. It is shown that the effective dielectric constant of such a plate depends not only on dielectric properties of the single-domain ferroelectric, but also on the geometrical characteristics of the system.