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The dielectric and magnetic properties of ceramics based on barium titanate and solid solutions of barium strontium titanate doped with iron and gadolinium ions at concentrations below 5 mol.% have...

The paper examines East Asia as regional civilization whose enduring characteristics emerged from long-term relations towards the Chinese model of a centralized state. The civilizational approach helps to understand the interrelation between different aspects of the region, such as politics, economy or culture. Chinese statehood relied on the principle of total power unrestricted by any norms of morality or laws and its neutralization by non-state institutions and informal networks. These two aspects helped to maintain a dynamic equilibrium of the political system and adapt it towards internal and external changes. The adoption of Chinese statehood came into contradiction with Korean and Japanese natural and social characteristics. This produced risks for the internal political legitimacy of political systems constructed according to the Chinese model in both countries. Necessity to preserve internal legitimacy encouraged external expansion of Imperial China and forced Korea and Japan to resist Sinocentric order but continue to adapt Chinese influence to local conditions. This contradiction defined reality of East Asian region during the traditional period, influenced its transition to modernity and remains relevant today.

Low-frequency vibration energy harvesting is becoming increasingly important for environmentally friendly and biomedical applications in order to power various wearable and implanted devices. In this paper, we propose the use of piezoelectric congruent LiNbO3 (LN) single crystals, with an engineered bidomain structure, as an alternative to the widely employed lead-based PZT. We thus compared experimentally the pure vibration energy scavenging performance of square-shaped bidomain and single-domain Y+128°-cut LN crystals and a conventional bimorph soft PZT ceramic bonded to long spring-steel cantilevers as a function of the frequency, load resistance, and tip proof mass. At a low bending resonance frequency of ca. 32.2 Hz, the bidomain LN yielded an open-circuit voltage of 1.54 kV/g, almost one order of magnitude larger than that observed in PZT. The maximum extractable average power was found to be of 9.2 mW/g2 in the bidomain LN, 6.2 mW/g2 in the single-domain LN, and 1.8 mW/g2 in the PZT piezo-elastic cantilevers. With five times higher output power density of up to 11.0 mW/(cm $^{3}\cdot \text {g}^{2}$ ) under resonance conditions, bidomain LN was thus shown to be a reliable lead-free and high-temperature alternative to PZT, thanks to its considerably larger quality factor and electromechanical conversion efficiency.

The efficiency of using the multicaloric effect (μCE) in solid-state cooling systems is investigated and compared with single caloric effects. The proposed approach is illustrated by the example of the Brighton cycle for μCE and the magnetocaloric effect. Based on the conducted experiments for the two-layer composite Fe48Rh52–PbZr0.53Ti0.47O3, the dependence of relative efficiency on temperature is constructed and the temperature range is estimated, where μCE has an advantage over the magnetocaloric effect. The comparison of the developed theory of the μCE with the obtained experimental data is performed.

The presence of a finite conductivity results in the appearance of an electric current proportional to the strength of the electric field. In turn, this current leads to the appearance of a...

The thermodynamic efficiency of using the multicaloric effect (μCE) in solid-state cooler systems has been studied in comparison to single-component caloric effects. This approach is illustrated by example of the Brayton cycle for μCE and magnetocaloric effect (MCE). Based on the results of experiments with Fe48Rh52–PbZr0.53Ti0.47O3 two-layer ferroic composite, the temperature dependence of the relative efficiency is determined and the temperature range is estimated in which the μCE is advantageous to MCE. The proposed theory of μCE is compared to experimental data.

Results are presented from measuring the volt–farad characteristics, temperature hysteresis, and current-voltage characteristics of capacitor structures based on Ba0.55Sr0.45TiO3 ceramics with 12 wt % magnesium additive (BST(M)). It is shown that the rate of temperature change has a substantial effect on the type of ferroelectric hysteresis. Values of the pyroelectric coefficients for BST(M) ceramics in the paraelectric phase ((2–8) × 10−4 C m−2 K−1) are determined. It is shown that in the absence of an external electric field, the temperature hysteresis could be due to the pyroelectric effect.

Nondestructive scanning probe microscopy of fragile nanoscale objects is currently in increasing need. In this paper, we report a novel atomic force microscopy mode, HybriD Piezoresponse Force Microscopy (HD-PFM), for simultaneous nondestructive analysis of piezoresponse as well as of mechanical and dielectric properties of nanoscale objects. We demonstrate this mode in application to self-assembled diphenylalanine peptide micro- and nanotubes formed on a gold-covered substrate. Nondestructive in- and out-of-plane piezoresponse measurements of tubes of less than 100 nm in diameter are demonstrated for the first time. High-resolution maps of tube elastic properties were obtained simultaneously with HD-PFM. Analysis of the measurement data combined with the finite-elements simulations allowed quantification of tube Young's modulus. The obtained value of 29 ± 1 GPa agrees well with the data obtained with other methods and reported in the literature.

Multiferroic materials are widely used in microelectronics because they are sensitive to elastic, magnetic, and electric fields and there is an intrinsic coupling between them. In particular, transition metal-doped BaTiO3 is considered as a viable multiferroic because of the simultaneous presence of ferroelectricity and magnetism. In this work, we study the electrical and thermal properties of Mn-doped BaTiO3 ceramics that can be used for multicaloric applications. We found that Mn doping leads to the broadening and shifting of the phase transition accompanied with simultaneous decrease of latent heat and entropy. Mn doping causes a decrease in the bulk resistivity while contact resistance remains intact. Doped ceramics can withstand high electric fields (up to 40 kV/cm) and exhibit linear I-V characteristics followed by the Schottky limited current in contrast to earlier observations. As such, these ceramics are promising for multicaloric applications.

This article discusses the effects of a simulated shoe made of different materials on providing protection against the influence of cryogenic gas, and considered local changes in heat flow and temperature curve along the length of the skin of the object of whole-body cryotherapy (WBC). In the work, protective shoes made of various materials, such as fabric, wool, leather and rubber, were considered and modeled. It was also shown that for a more effective WBC procedure, it is necessary to equalize the temperature dependence along the length of the object under study, since there are local excesses. The numerical analysis in this paper was carried out by simulating the process of nonstationary heat exchange through a multi-layer object; imitation of a person included such layers as: epithelium, fat layer, muscle layer. This problem was solved using the finite element method in special software. Assumptions were made to describe biological heat, the bioheat equations were solved using the Penns approximation. The cryogenic gas flow was described by a turbulent model. In this paper, a computer model is created that is close to reality with some assumptions, however, this model allows you to experiment without harming the patient to increase the therapeutic effect. The results can be used for the most convenient selection of protective shoes, as well as further to improve the efficiency and safety of the patient.

This paper discusses the dynamics of measuring the temperature of the integumentary tissues of a whole-body cryotherapy object (WBC). Studies have shown the need to use a protective layer on the lower extremities of the WBC object. Several types of protection were considered depending on the geometry, and the thickness and height of the protective layer varied. The physical processes occurring in cryosauna during cryotherapeutic effects on the human body are investigated. The analysis was performed by simulating the process of unsteady heat transfer through a multi-layer object. Research method. The study was performed by the finite element method. The calculations of heat transfer in a solid body, in a biological tissue with internal heat release and calculation of a turbulent flow were carried out. The modules were combined using the multiphysical interface of the software package. Main results. The created computer model made it possible to describe the dynamics of temperature fields in the skin of an object during the WBC process and after its completion. Frostbite of the lower extremities without a protective layer is shown, and the results of applying the protective layer of the WBC object are shown. Practical significance. The mathematical model allows estimating the influence of WBC parameters on the temperature field of the object under study. The results can be used to optimize the design of cryosaun, as well as to improve the efficiency and safety of the WBC, considering the individual characteristics of patients, as well as to improve the therapeutic properties during a WBC session.

Artificial extrinsic and intrinsic multiferroic structures were developed in the form of yttrium-iron garnet/barium-strontium titanate bi-layers and manganese-doped barium-strontium titanate films with a relatively high doping rate in the range of 10–20 mol%. For the experimental investigations, the planar capacitors were formed on the surfaces of the structures and the capacitance–voltage characteristics were measured. Structural characterization of the samples under study was based on X-ray diffraction analysis and film–substrate interfaces were investigated by X-ray photoelectron spectroscopy. The relative dielectric permittivity, dielectric loss tangent, and electric field tunability of the samples were measured in a temperature range from 77 to 300 К. The additional 6 and 3 % tuning of the dielectric permittivity by external magnetic field of 2000 Oe was demonstrated for the extrinsic and intrinsic structures, respectively.

The electric field generated by a scanning probe microscope is determined. Analytical expressions for the electroelastic field in a piezoelectric sample and the external electric field are derived for a spherical probe. It is demonstrated that the coupling of elastic and electrostatic fields in the piezoelectric material leads to energy redistribution between such fields. This circumstance causes variations in the normal component of the electric field strength at the interface and the capacitance of a probe.

Recently, much attention has been paid to the development of new microminiature solid-state cooling devices and heat energy converters based on the electrocaloric effect. But researchers pay little attention to aspects of the electrocaloric effect associated with its time and frequency characteristics. These phenomena must be taken into account when developing highly efficient thermodynamic cycles for solid-state cooling devices. In this work, we conducted an experimental study of the dependence of the electrocaloric response of a ferroelectric sample on the period and duty cycle of the control signal was studied. It was demonstrated, that value of electrocaloric response in studied ceramics may vary by more then 15% depending on period and duty cycle of electric pulses.

The study of novel thermal effects associated with spin current is fundamental to understanding the relationship between magnetoelectric and thermal phenomena. The central focus of attention of our research is on the spin analog of the Thomson effect as the most promising in terms of its use in heat switches of solid-state coolers. In order to model heat flows, the heat conduction equation is derived in the presence of magnetic and electric fields. Applying the developed theoretical framework, the spin Thomson coefficient is calculated for a yttrium-iron garnet plate. It is demonstrated that this coefficient strongly depends on the thickness of the plate. The corresponding estimates of the heat flux carried by the spins are also obtained. For a 200 nm plate, it is 6.81 W/cm2, which is comparable to the heat fluxes in the best thermal switches. Moreover, the results of the paper indicate at the possibility of further increase in the flux by an optimal choice of plate thickness and magnitude of magnetic field.

We investigated the magnetoelectric properties of a new laminate composite material based ony + 140°-cut congruent lithium niobate piezoelectric plates with an antiparallel polarized “head-to-head” bidomain structure and metglas used as a magnetostrictive layer. A series of bidomain lithium niobate crystals were prepared by annealing under conditions of Li2O outdiffusion from LiNbO3with a resultant growth of an inversion domain. The measured quasi-static magnetoelectric coupling coefficient achieved |αE31| = 1.9 V·(cm Oe)−1. At a bending resonance frequency of 6862 Hz, we found a giant |αE31| value up to 1704 V·(cm Oe)−1. Furthermore, the equivalent magnetic noise spectral density of the investigated composite material was only 92 fT/Hz1/2, a record value for such a low operation frequency. The magnetic-field detection limit of the laminated composite was found to be as low as 200 fT in direct measurements without any additional shielding from external noises.

The influence of UV and visible radiations on the insulating properties of metal-insulator-metal structures based on single-crystalline strontium titanate is investigated. It is found that the capacitance of the structure stably grows under irradiation by light with a wavelength from the intrinsic absorption range both at low temperatures and at room temperature. Mechanisms underlying this effect are discussed.

The results of investigations of the dielectric, magnetic, and structural properties of films with multiferroic properties have been presented. Two methods of the formation of multiferroic media have been analyzed: the method based on the formation of multilayer structures containing ferroelectric and ferromagnetic films and the method of introducing magnetic elements into a ferroelectric material in concentrations sufficient to induce magnetic properties in the composite material.

We have analyzed the electrocaloric response in ferroelectric materials in nonequilibrium thermal conditions. The temperature dependences of the electrocaloric response during polarization and depolarization of ferroelectric samples based on solid solutions of barium–strontium titanate and lead magnoniobate–titanate are considered. The difference in the electrocaloric responses for polarization and depolarization, which can be as large as 5 mK, has been demonstrated experimentally.

Korean Diaspora in the United States and Japan represent opposite patterns of ethnic boundaries reproduction in capitalist societies. Korean Americans developed their ethnicity as reaction to successful upward economic mobility. From the very beginning, the trust towards Korean immigrants was reflection of how well they were doing economically. However, this made Korean American Diaspora dependent on the contradictions of American society. The inevitable outcome of their economic activities (successful or not) was increase of racial/class tensions and conflicts that they could not ignore. Every economic activity represents temporal balance between scarcity and abundance and ethnic boundaries of Korean American Diaspora guarantee that scarcity of money and goods is once again present in American society, even for another ethnic group that motivates latter to pursue their own American dream. Japanese Koreans on the contrary developed moralized ethnic boundaries in response to social and economic exclusion. The disadvantaged status forces Japanese Koreans to mobilize their members for protest movements legitimized by the moralized image of Koreans in Japan as victims of discrimination. This does not always produce compassion among Japanese public but very often produces social irritations and eventually counter-protest movements that are also legitimized by moralized image of Japanese society as victim of Japanese Korean demands of compensations. Eventually this gives opportunity to Japanese Koreans to refer to unsuccessful attempts to obtain compensations and the cases of counter protest movement as a new proof of ongoing discrimination against their community to start this cycle of moral discontent once again.

Inconsistency between ethnic and national boundaries is reaction of Korean society to the pressure of modernization. At least since second half of 19th century growing influence of modern European nations and Japan forced political activists, intellectuals and peasants to try to shift from traditional hierarchically stratified society to absolutely different form of social organization as nation-state. It meant introduction of new principles of national and ethnic boundaries reproduction in form of recursive self-reproduction. It meant that social contradictions become major source of motivation to effectively exploit political and economic potential of Korean society. In this sense, political actions of each social group in Korea made nation-building process more dependent on disappointments and self-criticism because it increases contingency and thus create more possibilities to draw distinctions as a new source of motivation to modernize Korean society as nation. This helped political activists to return disappointed expectations into national discourse as political ideologies that permitted to preserve government’s legitimacy, legitimacy of idea of nation/ethnicity and motivate society to continue nation-building process. However, all social groups that pursued national unity faced lack of resources to implement the political and economic purposes of modernization. This forced them to rely on transnational resources whether as foreign assistance to promote further modernization inside Korea or emigration to other nations to implement expectations cultivated by modernizations outside Korea as ethnic minority.

Russia and China provide two opposite variations of Korean Diaspora ethnic boundaries formation within the context of socialist modernization. Socialist revolutions in Russia and China promised that taking power from the upper classes or the redistribution of wealth inside the national community would solve the problem of unequal distribution of wealth in society, which turned ethnic/national culture into a form of class struggle between labor and capital. Politicization of ethnicity demanded provision of Korean minority with its own national territory where they could enjoy a certain degree of autonomy, national schools, and national elites as a tool of dictatorship of the proletariat. Unlike China, Soviet/Russian government refused to provide territory to ethnic Koreans that defined further development. Logic of politicized Soviet/Russian Korean ethnicity constantly pressures to establish autonomy and at the same time resist its establishment. It meant that ethnic boundaries of Chinese Korean diaspora were reaction to different trends of political power in Yanbian Korean Autonomous Prefecture, Soviet/Russian Korean Diaspora developed in similar way but without politically guaranteed relation to certain territory that forced them to spread their activities in different regions all over the country.

North and South Korean diaspora politics developed as different reactions to inconsistency between ethnic and national boundaries. Each of them have to justify their political legitimacy as nation of Korean people in spite of the fact they do not include large number of Korean population who whether has their own nation or belong to other non-Korean nations as ethnic minority. Both North and South Korea apply different strategies of nation building formed within different patterns of modernization where diaspora politics plays crucial role. North Korea give example of socialist diaspora politics that search to exploit political potential of both North Korean society and overseas Koreans. It reproduces national unity of Korean people in terms of political contradictions that oscillates from inclusion of overseas Koreans into national boundaries to their exclusion depending on trend of political power in DPRK. Diaspora politics of the Republic of Korea on the contrary is largely aimed to exploit economic potential of both overseas Koreans and South Korean society. That is why it mostly focuses on reproduction of social inequalities between nation of origin and overseas Koreans to regulate inclusion or exclusion into/from national boundaries depending on their economic efficiency.

Barium titanate based ceramics is the most common class of lead-free ceramics due to its high values of dielectric constant, polarization, piezo- and electrocaloric effects. In this paper dielectric properties and electrocaloric effect in ceramics based on solid solution of barium-calcium titanate had been studied. It was shown, that increasing of calcium titanate in solid solution leads to increasing of dielectric constant and electrocaloric effect, simultaneouslyit leads to decreasing of leakage currents. While increasing fraction of calcium titanate from 0% to 10%, dielectric constant at frequency of 1 kHz rises from 10500 to 13600, maximum adiabatic electrocaloric response at ΔE = 1.3 V/μm rises from 0.5 K to 0.7 K.

The creation of devices based on the electrocaloric effect requires the methods for assessing pyroelectric currents at the different external parameters. Two indirect methods for calculating pyroelectric currents in ferroelectrics are considered. The first one based on the temperature-field dependences of the dielectric hysteresis loops. The second one based on the temperature-field dependences of the dielectric constant. The original method for directly estimating the magnitude of the pyroelectric currents by the charge change with thermal flux of laser radiation pulses is proposed.

Multiferroic materialsare widely used in microelectronics because they are sensitive to elastic, magnetic, and electric fields and there is an intrinsic coupling between them. In particular, transition metal-doped BaTiO3 is consideredas a viable multiferroic because of the simultaneous presence of ferroelectricity and magnetism.In this work, we study the electrical and thermal properties of Mn-doped BaTiO3 ceramics that can be used for multicaloric applications. We found that Mn doping leads to the broadening and shifting of the phase transition accompanied with simultaneous decrease of latent heat and entropy. Mn doping causes a decrease in the bulk resistivity while contact resistance remains intact. Doped ceramics can withstand high electric fields(up to 40 kV/cm) and exhibit linear I-V characteristics followed by the Schottkylimited current in contrast to earlier observations. As such, these ceramics are promising for multicaloric applications. © 2019 by the authors. Russian Science Foundation, RSF: № 18-19-00512 Funding: This work was supported by the Russian Science Foundation (grant № 18-19-00512).

A modified Weiss mean-field theory is used to study the dependence of the properties of a thin ferroelectric film on its thickness. The possibility of introducing gradient terms into the thermodynamic potential is analyzed using the calculus of variations. An integral equation is introduced to generalize the well-known Langevin equation to the case of the boundaries of a ferroelectric. An analysis of this equation leads to the existence of a transition layer at the interface between ferroelectrics or a ferroelectric and a dielectric. The permittivity of this layer is shown to depend on the electric field direction even if the ferroelectrics in contact are homogeneous. The results obtained in terms of the Weiss model are compared with the results of the models based on the correlation effect and the presence of a dielectric layer at the boundary of a ferroelectric and with experimental data.

The influence of the time mode of cooling, electric field and electrical conductivity on the thermal hysteresis loops in capacitor structures based on Ba0.55Sr0,45TiO3 (BST) ceramics with 12 wt.% magnesium orthotitanate Mg2TiO4 (BSTM) has been studied. The values of pyroelectric coefficients of the BSTM ceramics in the paraelectric phase were found to be between 2–8 · 10–4 C / (m2 ·K). The temperature hysteresis in the absence of an external electric field is caused by the pyroelectric effect. Different mechanisms responsible for the appearance of the thermal hysteresis are discussed.

The theoretical model of the ferroelectric domain wall motion has been developed. It is demonstrated that for a proper phenomenon description it is necessary to consider the thermoelectroelasticity gradient terms. It is shown that in the linear approximation the general solution of three-dimensional problem in transversely isotropic thermoelectroelastic media can be obtained by means of five newly introduced harmonic potential functions. As an example of the proposed model applicability, the electroelastic field induced by a sphere (SPM tip) located near a plane boundary of two half-spaces is considered and described.