Fine-grained (1 − x )BaTiO 3 – x Bi(Mg 0.5 Sn 0.5 )O 3 (abbreviated as BT- x BMS, x = 0.04–0.16) lead-free ceramics with single perovskite structure were fabricated by a traditional solid-state reaction route. The microstructures, dielectric behaviors, energy-storage performance and charge–discharge properties have been investigated. The increasing addition of BMS results in a transition from tetragonal to pseudo-cubic phase, accompanied with a decrease in average grain size. It shows typical relaxor-like behaviors at x > 0.04, which can be characterized by strong frequency dispersion and diffuse phase transition. The BT-0.12BMS ceramics exhibit optimum energy-storage performance with a recoverable energy density of 1.31 J/cm 3 at the electric field of 20 kV/mm. The excellent charge–discharge reliability over 10 5 cycles is also achieved at x = 0.12. The superior energy density and cycling stability indicate that the BT-0.12BMS ceramics have great potential for application in pulsed power systems. Meanwhile, this work interprets the mechanism of improved cycling stability in BaTiO 3 -based ceramics associated with domain configuration and defect structure.

Fine-grained (1 − x)BaTiO3–xBi(Mg0.5Sn0.5)O3 (abbreviated as BT-xBMS, x = 0.04–0.16) lead-free ceramics with single perovskite structure were fabricated by a traditional solid-state reaction route. The microstructures, dielectric behaviors, energy-storage performance and charge–discharge properties have been investigated. The increasing addition of BMS results in a transition from tetragonal to pseudo-cubic phase, accompanied with a decrease in average grain size. It shows typical relaxor-like behaviors at x > 0.04, which can be characterized by strong frequency dispersion and diffuse phase transition. The BT-0.12BMS ceramics exhibit optimum energy-storage performance with a recoverable energy density of 1.31 J/cm3 at the electric field of 20 kV/mm. The excellent charge–discharge reliability over 105 cycles is also achieved at x = 0.12. The superior energy density and cycling stability indicate that the BT-0.12BMS ceramics have great potential for application in pulsed power systems. Meanwhile, this work interprets the mechanism of improved cycling stability in BaTiO3-based ceramics associated with domain configuration and defect structure.

The stability of periodical domain structure during high-temperature annealing was studied in MgO doped lithium niobate single crystals by analysis of efficiency and homogeneity of the second harmonic generation (SHG) signal and optical visualization of the domain pattern. Annealing at temperatures up to 600 degrees C with up to 50 heating/cooling cycles resulted in weak changes of SHG performance and domain structure, while annealing at 1000 degrees C resulted in eight times decrease in the average SHG power and two times decrease in the effective periodical domain structure depth. Backswitching was attributed to the action of electric field induced by the crystal composition gradient caused by Li out-diffusion.

Barium strontium titanate glass-ceramics with different La2O3 contents (0, 0.5, 1.0, and 1.5 mol. %) were prepared by the melt-quenching technique. The phase developments, microstructures, and impedance behavior of these glass-ceramics have been investigated as a function of La2O3 content. By the X-ray diffraction study, a gradual change with increasing La2O3 content was observed. X-ray photoelectron spectroscopy indicated that the oxygen vacancy concentration decreases with the increase of La2O3 content. Lanthanum substitution resulted in an initial increase and then a decrease in the value of dielectric constant. From impedance spectroscopy, there are two electrical responses occurring: a low frequency response, which is related to the crystal-glass interface, and a high frequency response corresponding to the crystal phase. The low frequency peak shifts to lower frequencies and the high frequency peak shifts to higher frequencies with increasing lanthanum content. Both the temperature sensitivity of impedance and the value of ac conductivity decrease with the increase of La2O3 content.

The research was made possible by Russian Foundation for Basic Research (Grant 18-52-53032‐NNSF‐a). The equipment of the Ural Center for Shared Use “Modern Nanotechnology” Ural Federal University was used.

The microstructure and surface morphology of (Ba 0.8 ,Sr 0.2 )TiO 3 based glass-ceramics with different amounts of La and Ce were studied. It was shown that the addition of the 1.5% La and >2%Ce led to formation of dendrite-like structures. The isolated clusters of ferroelectric phase were found in all investigated samples. Fraction of ferroelectric phase was about 0.75% for La addition and 0.25% for Ce addition.

The bulk screening being the only possibility for decreasing residual depolarization field and stabilizing tailored domain structures is one of the main factors defining the domain kinetics in ferroelectrics. The bulk screening process was studied in lithium tantalate with lithium stoichiometry [Li]/([Li] + [Ta]) = 48.9%. The main parameters of bulk screening process were extracted from experimental data and compared with those of other representatives of lithium tantalate family. The linear dependence of the maximal value of bulk screening field on lithium stoichiometry was confirmed. The same stretched exponential power indicated that the underlying mechanism of bulk screening process did not change.

The effect of thermal annealing atmosphere on dielectric properties of barium strontium titanate glass ceramics was investigated by impedance analysis and thermally stimulated depolarization current measurement. As a result of impedance analysis, the resistances of both air-annealed and O-2-annealed glass ceramic samples were found to be two orders of magnitude higher than that of the as-sintered samples. This annealing atmosphere induced change in electrical properties can be ascribed to the variation in oxygen vacancy concentration. From the thermally stimulated depolarization current measurement, the annealing atmosphere dependence of current density was found for the annealed samples. It was shown that the reduction in oxygen vacancy concentration lowers the ac conductivity and defect dipole concentration.

We studied microstructure, surface morphology, and domain structure of (Ba0.75,Sr0.25)TiO3 based glass-ceramics with different amount of Mn additive (from 0 to 0.5%) prepared from melted and quenched mixed powders using several microscopic methods. The as-quenched sample was annealed and subjected to a controlled crystallization in air for 2h at temperatures 850 and 950°C. It was shown that the addition of the Mn up to 0.5% had no impact on morphology and domain structure. The dendrite structure was revealed in the samples crystallized at 850°C. The geometry of the clusters was analysed in terms of fractal approach. The faceted grains with size about 150 nm were found in ceramics annealed at 950°C. Individual grains demonstrated non-uniform piezoresponse, which could be attributed to existence of domain structure.

Thermally stimulated depolarization current (TSDC) experiments were carried out to investigate the effect of polarization temperature on different relaxation processes in barium strontium titanate glass-ceramics. It was found that all the TSDC curves are composed of four relaxation peaks. From the characteristics of peak temperature and peak current intensity with various polarization temperatures, the origin of these four peaks are identified as from defect dipole orientation, charge carrier detrapping, in-crystal oxygen vacancy migration, and trans-interface oxygen vacancy migration respectively. In addition, both the dipole concentration and trap density for the glass-ceramic samples were estimated.

The frequency doubling of femtosecond laser pulses in a two-dimensional (2D) rectangular nonlinear photonic lattice with hexagonal domains is studied experimentally and theoretically. The broad fundamental spectrum enables frequency conversion under nonlinear Bragg diffraction for a series of transverse orders at a fixed longitudinal quasi-phase-matching order. The consistent nonstationary theory of the frequency doubling of femtosecond laser pulses is developed using the representation based on the reciprocal lattice of the structure. The calculated spatial distribution of the second-harmonic spectral intensity agrees well with the experimental data. The condition for multiple nonlinear Bragg diffraction in a 2D nonlinear photonic lattice is offered. The hexagonal shape of the domains contributes to multibeam second harmonic excitation. The maximum conversion efficiency for a series of transverse orders in the range 0.01%-0.03% is obtained.

Here we present the results of the study of electromechanical performance of the Ce0.8Gd0.2O1.95 (CGO) self-supported thin circular membranes with aluminum and titanium as contact electrode materials. The electromechanical performance of both membranes was investigated using highly sensitive interferometric technique and showed two principal excitations mechanisms: common electrostriction and thermal contribution due to the Joule heating. Operating the membranes at frequencies about MHz results in significant contribution of the thermal excitation due to a large power dissipation for every electrode. The excitation of the membrane with aluminum electrodes at the frequencies about 1 Hz leads to the formation of the Schottky barrier at the interface with CGO. That is why the electromechanical response was almost independent on frequency and electric field. Membrane with titanium electrodes showed a prevalence of electrostriction effect with weak frequency dispersion and significant enhancement of the response with temperature.

Thermally stimulated depolarization current (TSDC) and highly accelerated lifetime testing studies of (Pb0.925-xLa0.05Bax)(Zr0.52Sn0.39Ti0.09)O3 (PLBZST) antiferroelectric ceramics have been performed for three compositions with different barium contents. These studies have revealed that barium substitution increases the failure time and improves the resistance degradation behavior. As a result of the variations of peak current intensity and peak temperature with different polarization temperatures in the TSDC curves, three successive relaxation peaks with different origins have been found to occur: a low-temperature defect dipole peak, an intermediate-temperature in-grain oxygen vacancy migration peak, and a high-temperature transgranular oxygen vacancy migration peak. These results demonstrate that the improved resistance degradation process with the increase of barium substitution is related to the decrease in oxygen vacancy concentration.

Doped ceria is known for decades as an excellent ionic conductor used ubiquitously in fuel cells and other devices. Recent discovery of a giant electrostriction effect has brought world-wide interest to this class of materials for actuation applications in micromechanical systems. From this aspect, the electromechanical response has to be studied as a function of external parameters, such as frequency, temperature, and electrode material. In this work, we fabricated circular membranes based on Gd-doped ceria (CGO) with Ti electrodes and studied their electromechanical response using a sensitive interferometric technique. The self-supported membranes are flat at room temperature and reversibly buckle upon heating, indicating that the membranes are under in-plane tensile strain. We have found that the electromechanical response is strongly frequency dependent. Significant hysteresis is observed in the displacement-vs.-voltage curves, which is deleterious for micromechanical applications but can be eliminated by tuning the phase of the excitation voltage. The electromechanical response of the system increases with temperature. Finite Element Modeling is applied to evaluate the electrostriction coefficient of the CGO material. At low frequencies, the M12 electrostriction coefficient is about 5 × 10−18 m2/V2, which is in line with the previous reports.

The depolarization process of glass-added barium titanate (BaTiO3) ceramics with two different glass concentrations was investigated using a thermally stimulated depolarization current (TSDC) technique. The TSDC spectra of the glass-added BaTiO3 ceramics show three peaks. The first sharp peak near the Curie temperature is due to pyroelectric current associated with ferroelectric-paraelectric phase transition. The middle temperature peak at about 200°C showed no dependence on the depolarization current peak position in the polarization field, and the activation energies of this peak were between 0.43 eV and 0.55 eV, which are attributed to the behavior of defect dipoles related to oxygen vacancies within the BaTiO3 grains. Moreover, the high temperature peak at around 300°C indicated that the depolarization current peak position depends on the polarization temperature and decreases with increasing polarization field. The activation energy of this high temperature peak was between 0.78 eV and 0.98 eV, which is similar to the activation energy for the motion of oxygen vacancies in perovskite oxides. The high temperature peak could be attributed to the migration of oxygen vacancies across grain boundaries. In this work we developed a model in which oxygen vacancies that originated from the defect within grains migrated from the anode to the cathode and some were trapped at the grain boundaries. It is presented here and successfully interprets the appearance and behavior of these peaks.

We present the recent achievements in periodical poling in MgO doped single crystals of lithium niobate and lithium tantalate used for second harmonic generation and optical parametric oscillation based on quasi-phase-matched nonlinear optical wavelength conversion. The compact and highly efficient sources of visible and mid-IR laser light have been developed.

During the last decades, potassium titanyl phosphate (KTP) and its isomorphs have attracted much attention due to its application in various photonic devices. These materials possess large nonlinear optic and electro-optic coefficients, high optical damage threshold, as well as broad thermal and angular acceptance for second harmonic generation. The interest to increase of the frequency conversion efficiency by domain engineering in the crystals of KTP family is enormous. This paper provides an overview of the available data dedicated to study of the domain structure and creation of the periodical domain patterns in crystals of KTP family for nonlinear optical devices.

The natural ability of peptides and proteins to self-assemble into elongated fibrils is associated with several neurogenerative diseases. Diphenylalanine (FF) tubular structures that have the same structural motif as in Aβ-amyloid peptide (involved in Alzheimer's disease) are shown to possess remarkable physical properties ranging from piezoelectricity to electrochemical activities. In this work, we also discover a significant pyroelectric activity and measure the temperature dependence of the pyroelectric coefficient in the temperature range of 20–100 °C. Pyroelectric activity decreases with temperature contrary to most ferroelectric materials and significant relaxation of pyrocurrent is observed on cooling after heating above 50 °C. This unusual behavior is assigned to the temperature-induced disorder of water molecules inside the nanochannels. Pyroelectric coefficient and current and voltage figures of merit are estimated and future applications of pyroelectric peptide nanostructures in biomedical applications are outlined.

ФЦП «Исследования и разработки по приоритетным направлениям развития научно-технологического комплекса России на 2014-2020 годы». Соглашение о предоставлении субсидии от 11 ноября 2015 г. № 14.587.21.0022 с дополнительным соглашением от 24 июня 2016 г. № 1.