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This paper presents the results of the study of the domain structure of barium titanate crystals in a wide temperature range including the Curie point (TC) using the polarization-optical method in the reflected light and the force microscopy of the piezoelectric response. It is shown that a new a–c domain structure forms during cyclic heating of the crystal above TCand subsequent cooling to the ferroelectric phase. The role of uncompensated charges appeared on the crystal surface during the phase transition and their influence on the formation of the domain structure during cooling are discussed.

A study of the polarization reversal processes in TGS crystals doped by both Cu and Cr ions is presented. It is shown that Cr ions manifest themselves as active additives and their effect on polarization reversal processes is stronger as compared with Cu ions. At the same time Cu ions improve the polarization reversal characteristics of TGS.

The combined effect of uniaxial mechanical compression and gradient heating on the pyroelectric properties and domain structure realignment processes in gadolinium molybdate single crystals has been studied. It is shown that the application of mechanical stresses under the condition of gradient heating results in a stabilization of the polarized state and in a shift of the phase transition point towards higher temperatures.

In this paper the results of dielectric dispersion and electrophysical properties investigations of monoclinic Tellurium Acid Ammonium Phosphate (TAAP) single crystal in wide range of temperatures and frequencies are presented. Another goal of this study was to test experimentally the ''universal law'' of dielectric relaxation of solids. Obtained results show up some features of a phase transition and the ''universal law'' is satisfied.

We have investigated the dielectric properties of ceramics on PFN base with violated stoichiometry of its composition in lead, iron and niobium.

The review of the results of investigations of domain structure realignment processes and phase transitions in pure and mixed ferroelastics under the influence of mechanical stresses and temperature gradients is given in this work.

AbstractThe submitted paper is the review of the data on processes of domain structure realignment of pure & doped TGS crystals and the role of the Barkhausen effect in these processes. Among given results some have been published and some are quite new.

Pyroelectric properties of triglycine sulphate (TGS) single crystals doped with Co, Cu, and Tl ions were studied. In crystals containing less than 5 × 10-5 wt% of impurities, an increase of pyroelectric coefficient and magnitude of reorienting polarization is observed as compared with those in pure TGS. Larger doping concentrations lead to decrease of these parameters. Anomalous pyroelectric hysteresis loops are observed in some cases. Thermal Barkhausen effect (TBE) was also studied. On this basis it was found that the temperature of most intense depoling drops for doped TGS crystals in comparison with pure ones. The nature of observed concentration dependence of pyroelectric properties is interpreted on the same ground as the radiation-induced changes in ferroelectric properties. TBE is analyzed in terms of depolarizing fields of bounded charges, occurring due to temperature gradients in the crystal.

Influence of the heating rate on domain structure realignment processes and associated phenomena in gadolinium molybdate is studied by means of thermal Barkhausen effect, polarized microscopy, pyroelectric current measurements, selective etching. It is shown that the phase transition temperature is lowered when the heating rate is increased. It is supposed that observed effects are associated with mechanical stretching strains in the sample due to heating inhomogenities.

The temperature induced domain structure realignment processes in pure ferroelastic lead orthophosphate with no external mechanical stresses have been studied in detail. A functional dependence of the phase transition point on the heating rate has been thus evidenced for this crystal.

Pyroelectric and dielectric properties and switching of ferroelectric PLZT ceramics have been studied in the range 290-470 K. The effect of γ-irradiation on pyroelectric coefficient, dielectric permittivity and rate of Barkhausen jumps sequence at polarization switching of PLZT ceramics is found to be most pronounced at phase transition.

Literature data on the characteristics of different types of ferroelectric materials are reviewed together with the results of own studies. The emphasis is made on the performance of these materials in pyrovidicon targets.

The mechanisms of polarization reversal jumps and their interrelation with general features of the Barkhausen effect are discussed in the present work. By means of the new modification of the Barkhausen effect - the thermal Barkhausen effect - the kinetics of domain structure reorientation in ferroelectric crystals TGS and TGSe has been examined in the wide temperature range. The investigation of the Barkhausen effect in a single crystal of improper ferroelectric sodium trihydroselenite has also been performed.

Processes of the domain structure (DS) realignment in PLZT ferroelectric ceramics are studied in a broad temperature range. It is established that in samples of polarized ceramics changes of temperature are accompanied by the DS realignment in the absence of the electric field. The intensity of domain processes depends on the mode of sample polarization.

The increasing interest in utilizing of ferroelectric-ferroelastic crystals in functional microelectronic devices1 is brought about by the existence of domain structure in these materials and possibilities of controlling it by external physical fields.