A. F. Semenchev

Domain structure of multiaxial ferroelectric crystals

Abstract It has been shown and exemplified by model crystals, that domain structure is a consequence of the mechanical, electrical and thermal effects occurring in a two-phase (paraelectric/ferroelectric) crystal. General rules that goven domain structure formation have been formulated.

The switching of PbTiO3 crystals

Abstract The interrelation is ascertained between the character of 180° switching in PbTiO3 single crystals and the type of dependencies in pulsed fields.

The domain structure formation at phase transitions

The connection between the phase transition conditions and the domain structure of BaTiO3 and PbTiO3 crystals is determined.

Phase transition and switching in lead titanate crystals

Abstract Different phase-front shapes are described with respect to conditions of phase transition. An explanation of the origin of so-called reciprocal domains is proposed. These domains are shown to be stable against an effect of applied field. Phase transition behavior of lead titanate crystals is defined by i. A high conductivity near the Curie point, [sgrave] Tc ∼ 10−3 (ohm. cm)−1 (carrier concentration n ∼ 1018 cm−3); ii. phase-front conditions, i.e., a large elastic stress due to a change in unit-cell volume, VTC ∼ 0.3 A3, (c/a - 1)TC ∼ 0.012, with a large change in spontaneous polarization, Ps ∼ 40 μCI cm2 [l], and iii. conditions of phase transition, i.e., temperature-gradient direction with respect to crystal axes, (grad T)Tcmagnitude of temperature gradient and phase-front velocity. Consider the effect of these factors on the transition behavior, domain structure and switching process. Due to a high conductivity of lead titanate at the transition, the phase front is flat, which is characteristi...

X-Ray, Optical and Dielectric Studies of Diffused Phase Transitions in NaNbO3-Based Solid Solution Crystals

In flux-grown (1−x)NaNbO3-(x)Gd1/3NbO3 solid solution crystals a diffusion of the dielectric permittivity ϵ maximum grows with x and increases dramatically when x exceeds a threshold value x0 ≈ 0.1. Optical studies by the rotating-polarizer method show that Gd-doping results in a very small mean size of twins and the distribution of the birefringence image becomes very messy. In the x < x0 range the changes of lattice parameters and birefringence corresponding to the ϵ(T) anomaly were revealed. The results obtained are in line with the assumption that phase transition diffusion in NaNbO3 is a result of the local strains stemmed from the impurities.

Regularities in domain structure formation in multiaxial ferroelectric crystals

Abstract A description is given of basic regularities in the formation of domains and twins during phase transformation involving movement of a single plane phase boundary.

Studies of Domain and Twin Patterns in NaNbO3-Gd1/3NbO3 Solid Solution Crystals

Studies of (1-x)NaNbO3-xGd1/3NbO3 crystals in polarized light revealed the independence of the temperature of rotational phase transition into the cubic phase on x. This correlates with the similarity of Na+ and Gd3+ ionic radii. Increase of Gd content leads to the diffusion of permittivity maxima and a dramatic decrease of a mean size of twins (domains). This makes both crystallooptic studies and rotating polarizer method ineffective. Multifractal analysis of false-colour image patterns obtained by rotating polarizer method, using the Metripol microscope system enables to detect the changes in domain (twin) pattern in the temperature range of diffuse phase transition.

Effect of illumination on switching process in PbTiO3 crystals

Abstract The effect of photoassisted domain switching depending on irradiating light was found in PbTiO3 crystals.

Minor Dielectric Anomalies in ANbO3 (A-Li, Na, K) Single Crystals in the 100–300°C Temperature Range

In ANbO3 (A-Li, Na, K) single crystals besides dielectric permittivity ϵ maxima, corresponding to the known ferroelectric and antiferroelectric phase transitions, minor ϵ (T) anomalies were observed in the 100–300°C temperature range. The temperature T a of these anomalies does not depend on measuring frequency in the 102–106 Hz range. Dilatometric studies showed that temperature dependences of relative dilatation Δ L/L have an inflexion in the vicinity of T a . Linear correlation between T a and the temperature T PE of the phase transition into the paraelectric phase was revealed. It is supposed that the minor ϵ (T) anomalies observed in ANbO3 crystals in the 100–300°C temperature range are due to phase transitions to the incommensurate phase.

General rules in domain structure formation during phase transition in multiaxial ferroelectrics

Abstract The consequences of mechanical, electrical and thermal events in a two-phase (paraelectric-ferroelectric) crystal have been analyzed. General rules which govern domain structure formation have been formulated.