Authors:Tejkaran Narolia, Vijay K. Gupta, I. A. Parinov Abstract: Journal of Advanced Dielectrics, Ahead of Print. A shear mode piezoelectric energy harvester for harvesting energy from rotary motion is developed. The kinetic energy in the form of rotation is converted into electrical form of energy by piezoelectric principle with oscillation of piezoelectric patch through magnetic shear force. Efforts have been made to increase the output power using shear mode of operation. In order to estimate the induced voltage of piezoelectric patch, a mathematical model and an Finite Element (FE) model are developed. Considering various parameters, optimization of the harvester was made. Analytical and Finite Element Method (FEM) results are compared and good agreement has been found. The total average output power of 358.44 W is generated when rotary speed of hub of about 600 RPM. Citation: Journal of Advanced Dielectrics PubDate: 2020-06-30T07:00:00Z DOI: 10.1142/S2010135X20500083

Authors:G. A. Geguzina Abstract: Journal of Advanced Dielectrics, Ahead of Print. The experimental and calculated data on the existence of complex oxides in solid state with the octahedral structures of four families, namely perovskites, Bi-containing layered perovskite-like ones, tetragonal tungsten bronzes and pyrochlores, and about their phase transitions are systematized and summarized on the basis of the quasi-elastic or geometric models of these structures. It has been established that similar existence areas and similar correlations between the interatomic bond strains in their structures, on the one hand, and the temperatures of their ferroelectric or antiferroelectric phase transitions, on the other hand, are observed for all of them, despite the differences in the compositions and structures of these oxides, but taking into account their similar parameters. Citation: Journal of Advanced Dielectrics PubDate: 2020-06-17T07:00:00Z DOI: 10.1142/S2010135X20600139

Authors:Yu. I. Yurasov, A. V. Nazarenko Abstract: Journal of Advanced Dielectrics, Ahead of Print. This paper is focused on the comparison of the results of various approximation models describing the frequency dependences of the dielectric constant [math] and [math], the tangent of the loss angle tg[math] and the electrical conductivity [math] and [math] of nonlinear dielectrics. The classic ferroelectric material of the PZT system with [math] was chosen as the object of study. Based on the analysis of temperature-frequency dependences of the “empirical” parameters [math] and [math], a regularity has been revealed that allows them to be calculated. A new relationship has been established through the parameter [math], which allows to relate the temperature and frequency dependences of the complex electrical conductivity as [math] and as [math] in the Havriliak–Negami approximation models and in the new model for the description of the complex electrical conductivity [math]. It is shown that [math] is a parameter of the temperature-frequency distribution of dielectric losses. Using the obtained expressions, a new theoretical description of experimental spectra having a relaxation character was proposed. It has been proven that the use of the new model makes it possible to accurately describe the set of studied spectra, including the high and low frequencies, in the frequency range from 10[math] to 108[math]Hz. Citation: Journal of Advanced Dielectrics PubDate: 2020-06-16T07:00:00Z DOI: 10.1142/S2010135X20600061

Authors:V. A. Chebanenko, I. V. Zhilyaev, A. N. Soloviev, A. V. Cherpakov, I. A. Parinov Abstract: Journal of Advanced Dielectrics, Ahead of Print. This paper presents the application of the Pareto-based multicriteria optimization technique to problems of increasing the efficiency of piezoelectric generators (PEGs). The optimization problem was solved for two types of generators: cantilever and stack. For the cantilever generator, the task was to optimize the design in such a way as to obtain the maximum output power for a given mechanical excitation. The optimization process was divided into several stages, which significantly reduced the amount of calculations. The task of optimizing the stack type for a given form of mechanical loading consisted in finding the geometric parameters of the generator at which the output voltage and power would be maximum. In the result of solving both problems, sets of geometric design parameters of PEGs were obtained, on the basis of which efficient transducers can be developed for specific operating conditions. It turned out that this technique is more suitable for optimizing the design of cantilever generators than for stack ones in given constraints. The solution of both problems was realized using the finite element method. Citation: Journal of Advanced Dielectrics PubDate: 2020-06-15T07:00:00Z DOI: 10.1142/S2010135X20600164

Authors:Sidorenko Eugeny, Chan Thi Beat Ngoc, Prikhodko Gennady, Natkhin Ivan, Shloma Alexander, Kharchenko Diana Abstract: Journal of Advanced Dielectrics, Ahead of Print. The effect of a constant electric field ([math]) on the absorption of microwave electromagnetic energy ([math]) by BaTiO3 crystals and the highly sensitive PCR-1 piezoceramic was studied. The field dependence of the absorption value [math] at the maximum of the spectrum [math] has the form of a “butterfly”, and the dependence of the frequency shift of the maximum on the field strength [math] has a hysteretic character. The PCR-1 [math] absorption spectrum at high [math] is modulated by pulses in a wide frequency range. It is assumed that the cause of the amplitude–frequency modulation of the spectrum may be the electromagnetic radiation of incomplete local discharges at the surface of piezoceramics. The change in the magnitude and position of the resonance maximum in the absorption spectra and the appearance of amplitude–frequency modulation [math] when exposed to a constant field is interpreted from the point of view of changes in the parameters and concentration of the domains walls, as well as the [math]- and [math]-domain wedges of mechanical twins resonating in the electromagnetic field. Citation: Journal of Advanced Dielectrics PubDate: 2020-06-15T07:00:00Z DOI: 10.1142/S2010135X20600206

Authors:Linganaboina Srinivasa Rao, Chinthakuntla Thirmal, Parchuri Raghavendra Rao Abstract: Journal of Advanced Dielectrics, Ahead of Print. 40 Li2O–5 WO3–(55-[math]) B2O3: [math]V2O5 (mol%) for [math] glasses were prepared by melt-quenching. Electric polarization was described in terms of the dielectric constant ([math]) and loss ([math]). Mixed conduction phenomenon was explained by redox pairs [math] and [math] at high temperatures. Electronic polarizability ([math]) was determined over a range of frequencies (100[math]Hz–100[math]kHz) and temperatures (30–[math]C). The change of boron coordination in the glass network was explained with the aid of temperature coefficient of polarizability ([math]). Nonlinear susceptibility ([math]) and optical band gap ([math]) were studied as a function of concentration of V2O5. The highest values of [math] and [math] were obtained at [math][math]mol%. These glasses may find potential practical applications in the fields of solid-state ionics and nonlinear optics. Citation: Journal of Advanced Dielectrics PubDate: 2020-06-12T07:00:00Z DOI: 10.1142/S2010135X2050006X

Authors:E. M. Bayan, T. G. Lupeiko, L. E. Pustovaya, M. G. Volkova Abstract: Journal of Advanced Dielectrics, Ahead of Print. Sn-doped TiO2 nanomaterials were synthesized by sol–gel method. It was shown the phase compositions and phase transitions change with the introduction of different tin amounts (0.5–20[math]mol.%). X-ray powder diffraction was used to study the effect of different tin amounts on the anatase–rutile phase transition. It was found that the introduction of ions increases the thermal stability of anatase modifications. The material’s photocatalytic activity was studied in reaction with a model pollutant (methylene blue) photodegradation under UV and visible light activation. The best photocatalytic properties were shown for material, which contains 5[math]mol.% of Sn. Citation: Journal of Advanced Dielectrics PubDate: 2020-06-12T07:00:00Z DOI: 10.1142/S2010135X20600188

Authors:S. V. Zubkov Abstract: Journal of Advanced Dielectrics, Ahead of Print. The structural and electrophysical characteristics of a number of solid solutions of layered oxides of the perovskite-type Bi7Ti[math]WxNb[math]V[math]O[math] ([math]) are studied. According to X-ray powder diffraction data, all the compounds studied are single-phase and have the structure of Aurivillius phases ([math]) with a rhombic crystal lattice (space group I2[math]cm, [math]). Changes in tetragonal and rhombic distortions of perovskite-like layers in compounds were considered depending on their chemical composition. The temperature dependences of the relative permittivity [math] (T) were measured. It was shown that the Curie temperature [math] of the perovskite-type oxides Bi7Ti[math]WxNb[math]V[math]O[math] ([math]) linearly decreases with increasing parameter [math]. The activation energies of charge carriers were obtained in different temperature ranges. It was found that there are three temperature regions with very different activation energies due to the different nature of the charge carriers in the studied compounds. The effect of substitution of Nb[math] ions by V[math] ions is investigated. It was found that for a number of compounds, the substitution of niobium ions by vanadium ions led to an increase in the dielectric constant and a decrease in the dielectric loss tangent. Citation: Journal of Advanced Dielectrics PubDate: 2020-06-10T07:00:00Z DOI: 10.1142/S2010135X20600085

Authors:O. B. Shcherbina, S. M. Masloboeva, N. I. Steblevskaya, M. V. Belobeletskaya, V. V. Efremov, M. V. Smirnov, M. N. Palatnikov Abstract: Journal of Advanced Dielectrics, Ahead of Print. Ceramic solid solutions GdNbxTa[math]O4 ([math]–1) were synthesized by sol–gel. Morphological particularities of microstructure were studied, strength characteristics (Young’s modulus) and stress intensity factor for mode I [math] were evaluated. The latter is a criterion of crack resistance of the material. Luminescent properties of solid solutions GdNbxTa[math]O4 were researched under UV exciting radiation. A comparatively small addition of Ta ([math]) was shown to increase luminescence intensities of centers Nb[math]–O−. An addition of Ta to GdNbO4 leads to creation of solid solution GdNb[math]Ta[math]O4. Intensity of these centers is 3–6.5 times larger than that of GdNbO4 and GdTaO4. Citation: Journal of Advanced Dielectrics PubDate: 2020-06-10T07:00:00Z DOI: 10.1142/S2010135X20600140

Authors:T. I. Belyankova, E. I. Vorovich, V. V. Kalinchuk, O. M. Tukodova Abstract: Journal of Advanced Dielectrics, Ahead of Print. A model of a piezoelectric structure with an inhomogeneous coating is considered. The structure is a homogeneous half-space made of PZT-5H ferroelectric ceramics with a functionally graded coating. The properties of coating vary continuously in thickness from parameters of one material to parameters of another material in a continuously nonmonotonic or piecewise-continuous manner. As coating materials, various combinations of ceramics of different stiffness based on PZT are considered. Using the example of the problem of the propagation of sh-waves in a piezoelectric structure, we studied the influence of the ratio of the physical parameters of the coating materials, the localization region, and the size of the transition zone of one material to another on the propagation features of surface acoustic waves (SAWs) and the structure of the wave field. Citation: Journal of Advanced Dielectrics PubDate: 2020-06-10T07:00:00Z DOI: 10.1142/S2010135X20600176

Authors:N. Gaponenko, D. Parafinyuk, P. Kholov, T. Raichenok, S. Prislopski Abstract: Journal of Advanced Dielectrics, Ahead of Print. Sol–gel technology was applied to fabricate Eu-doped BaTiO3/SiO2 multilayer structures by spinning on silicon and fused silica substrates. Eu photoluminescence (PL) was investigated depending on the annealing temperature of these structures. The samples demonstrate the room temperature luminescence corresponding to 5D[math]FJ ([math], 2, 3, 4) transitions of trivalent europium with the most intensive band at 615 nm. For the structure on fused silica with Eu in the BaTiO3 cavity, increase of the annealing temperature from [math]C to [math]C results in modification of the luminescence indicatrix and lowering of the luminescence intensity in the direction along the surface normal. For BaTiO3/SiO2 multilayer structure generated on silicon, scanning electron microscopy (SEM) analyses reveal disordering after annealing at [math]C. This heat treatment provides also an increase of the Eu luminescence intensity. Citation: Journal of Advanced Dielectrics PubDate: 2020-06-04T07:00:00Z DOI: 10.1142/S2010135X20500058

Authors:Andryushin Konstantin, Andryushina Inna, Sadykov Khizir, Nagaenko Alexandr, Reznichenko Larisa Abstract: Journal of Advanced Dielectrics, Ahead of Print. This paper presents the results of a comprehensive study of the industrially produced ferro-piezoelectric ceramic material based on the PbZrO3-PbTiO3-PbMn[math]Nb[math]O3-PbZn[math]Nb[math]O[math] system. Studies have confirmed that this material refers to ferro-rigid materials with high coercive fields, stable dielectric properties in a wide temperature range, practically no Curie temperature hysteresis, as well as low controllability of the dielectric constant and deformation characteristics by constant bias electric fields. The revealed correlation between dielectric, deformation characteristics and dielectric hysteresis allows us to consider this material as promising for devices operating in power modes: piezotransformers, highly loaded ultrasonic devices, piezoelectric motors, etc. Citation: Journal of Advanced Dielectrics PubDate: 2020-06-04T07:00:00Z DOI: 10.1142/S2010135X20600127

Authors:Skaliukh Alexander Abstract: Journal of Advanced Dielectrics, Ahead of Print. A three-dimensional mathematical model is proposed that describes the ferroelectric response of polycrystalline ferroelectrics to an electric field in the absence of mechanical stresses. It is based on the separation of the switching process into two related parts: the rotation of the spontaneous polarization vectors and the destruction of the domain wall fixing mechanisms. For each of the parts, the energy costs are calculated, which are the components of the energy balance in the real polarization process. The constitutive relations for the induced and residual components of the polarization vector of the representative volume are obtained. A number of numerical experiments were performed, which showed good agreement with the experimental data. Citation: Journal of Advanced Dielectrics PubDate: 2020-06-04T07:00:00Z DOI: 10.1142/S2010135X20600152

Authors:Sidek Khasbulatov, Suleiman Kallaev, Haji Gadjiev, Zairbek Omarov, Abumuslim Bakmaev, Iliya Verbenko, Aleksey Pavelko, Larisa Reznichenko Abstract: Journal of Advanced Dielectrics, Ahead of Print. The paper presents the results of a comprehensive study of the thermophysical properties (thermal conductivity, thermal diffusivity, heat capacity) of high-temperature multiferroic BiFeO3 modified with rare-earth elements (REEs) (La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Lu). The regularities of the formation of the mentioned characteristics were established. The assumptions about the nature of the observed phenomena were suggested. Citation: Journal of Advanced Dielectrics PubDate: 2020-06-04T07:00:00Z DOI: 10.1142/S2010135X2060019X

Authors:S. I. Raevskaya, S. P. Kubrin, Jian Zhuang, I. P. Raevski, M. A. Malitskaya, I. N. Zakharchenko, M. S. Panchelyuga, V. V. Titov Abstract: Journal of Advanced Dielectrics, Ahead of Print. 0.5[math]FeO3–0.5NaNbO3 ([math], La) solid solution compositions were prepared using a solid phase reaction route from high-purity starting oxides. Mössbauer studies have shown that while for 0.5BiFeO3–0.5NaNbO3 the magnetic phase transition temperature [math] value is about 150[math]K, for 0.5LaFeO3–0.5NaNbO3, it is only [math][math]K. This dramatic difference in [math] values seems to be due to additional contribution of the magnetic superexchange between Fe[math] ions via the empty 6p-states of Bi[math] ions to the overall superexchange. Citation: Journal of Advanced Dielectrics PubDate: 2020-06-02T07:00:00Z DOI: 10.1142/S2010135X2060005X

Authors:G. Ya. Karapetyan, V. E. Kaydashev, M. E. Kutepov, T. A. Minasyan, V. A. Kalinin, V. O. Kislitsyn, E. M. Kaidashev Abstract: Journal of Advanced Dielectrics, Ahead of Print. A tunable high-Q surface acoustic wave (SAW) resonator in the form of several parallel-connected interdigital transducers loaded on a varying capacitance on lithium niobate substrates was developed and studied. The working frequency range was 90–2450[math]MHz. A method of calculating such resonators, considering losses in the metal film as well as losses due to the propagation of SAWs and transformations into bulk waves is proposed. Such a design allows one to obtain a quality factor over 5000 in the frequency range 2400–2483[math]MHz. The resonant frequency shifts by 600[math]kHz when the capacitance changes by [math]% of the value of 21[math]pF (or 32[math]ppm/pF) and has an almost linear character. Citation: Journal of Advanced Dielectrics PubDate: 2020-05-11T07:00:00Z DOI: 10.1142/S2010135X20600097

Authors:G. Ya. Karapetyan, I. A. Parinov, G. Parchi Abstract: Journal of Advanced Dielectrics, Ahead of Print. A thermoelectric transducer based on MDSM structures of the field-effect transistor (FET) type is proposed, in which the thermal energy of the environment is converted into electrical energy. We use a new principle of converting thermal energy into electrical energy. We show that with the help of such a converter, it is possible to dramatically increase the efficiency of processors due to the heat generated by the processor is converted by this converter again into electricity that transfers to the processor. Citation: Journal of Advanced Dielectrics PubDate: 2020-05-07T07:00:00Z DOI: 10.1142/S2010135X20600073

Authors:Yu. N. Zakharov, V. P. Sakhnenko, I. A. Parinov, I. P. Raevsky, M. A. Bunin, V. A. Chebanenko, M. A. Zaerko, E. I. Sitalo, A. A. Pavelko, L. I. Kiseleva Abstract: Journal of Advanced Dielectrics, Ahead of Print. It has been established that in plates made of hot-pressed ferroelectric ceramics PZT-19 ([math]C), after metal electrodes from Ag are burned into opposite surfaces with different depths of mechanical damage, counter-directional stationary deformation gradients and, accordingly, internal electric displacement fields create a stationary flexoelectric effect. As a result, unpolarized ceramics below the Curie temperature become a pyroelectric, and above it become a pyroelectric bolometer. After polishing the less damaged surface and replacing the Ag (valency [math]) electrode with Cr ([math]) by thermal evaporation in vacuum from the intact surface, a new thermally stable polarization is created, directed from the damaged surface in the interelectrode volume. Such plates have an asymmetric dielectric hysteresis loop, retain the values of the pyroelectric effect and piezoelectric effect in the ferroelectric phase, as well as the bolometric effect in the paraelectric phase after repeated heating cycles to [math]C and cooling to [math]. Citation: Journal of Advanced Dielectrics PubDate: 2020-05-06T07:00:00Z DOI: 10.1142/S2010135X20600103

Authors:S. V. Zubkov Abstract: Journal of Advanced Dielectrics, Ahead of Print. The Aurivillius phases (APs) [Bi2O2][math][[math]O[math]][math] are well-known ferroelectrics with high Curie temperatures. High-temperature piezoceramics Bi[math]GdxTiNbO9(BiGdTiNb, [math], 0.1, 0.2, 0.3) were prepared by a solid-state reaction method. The structural and electrophysical characteristics of BiGdTiNb ceramics have been studied. According to the data of powder X-ray diffraction, all the compounds are single-phase with the structures of two-layer APs ([math]) with the orthorhombic crystal lattice (space group [math]). The temperature dependence of the relative permittivity [math] (T) of the compounds was measured and showed that the Curie temperature of perovskite-like oxides Bi[math]GdxTiNbO9 increases linearly with an increase in the substitution parameter [math] to [math]C. The activation energies of charge carriers have been found in different temperature ranges. Citation: Journal of Advanced Dielectrics PubDate: 2020-04-24T07:00:00Z DOI: 10.1142/S2010135X20600024

Authors:Aleksey Pavelko, Lidiya Shilkina, Larisa Reznichenko Abstract: Journal of Advanced Dielectrics, Ahead of Print. Phase diagrams were constructed (at room temperature), the dielectric, piezoelectric, elastic and reversible properties of the Ge-modified [math]PbTiO3–[math]PbZrO3–[math]PbNb[math]Mg[math]O3 multicomponent system ceramics were studied. The data obtained are compared with the results of studies of solid solutions of basic binary systems, as well as with the results obtained previously for other sections of the system under consideration. A significant increase in the width of the morphotropic region, diffusion of the concentration dependences of the electrophysical characteristics, and an increase in stability under the influence of constant bias fields in the solid solutions of the studied system were established. Citation: Journal of Advanced Dielectrics PubDate: 2020-04-24T07:00:00Z DOI: 10.1142/S2010135X20600115

Authors:M. V. Talanov, A. A. Pavelko, L. A. Reznichenko Abstract: Journal of Advanced Dielectrics, Ahead of Print. The electromechanical responses of multicomponent solid solutions Pb[math]Ba[math](Mg[math]Nb[math])[math](Zn[math]Nb[math])[math](Ni[math]Nb[math])[math]Ti[math]O3 in low and high electric fields were studied. In both cases, significant electromechanical responses are observed. In particular, the maximum values of the large-signal piezoelectric coefficient [math] reach 1600[math]m/V at very low values of the electric field ([math]5[math]kV/cm). The observed features of the electromechanical responses of the studied ceramics are advantages in terms of their possible application in actuators. Citation: Journal of Advanced Dielectrics PubDate: 2020-04-17T07:00:00Z DOI: 10.1142/S2010135X20600048

Authors:Zamir S. Khan, M. P. Lokhande, Avadhut Deshmukh, A. C. Kumbharkhane Abstract: Journal of Advanced Dielectrics, Ahead of Print. The Complex permittivity spectra of glycol ether (GE) compounds such as ethylene glycol mono-methyl ether (EGME) with water mixture over entire concentration range and in temperature range of 10–25∘C have been determined using Time Domain Reflectometry (TDR) technique in the frequency range 10[math]MHz to 50[math]GHz. The complex permittivity spectra for EGME-water were fitted in the Cole–Davidson model. The Static dielectric constant ([math], Relaxation time ([math], effective Kirkwood correlation factor ([math], excess permittivity ([math], thermodynamic parameters (activation enthalpy and activation entropy) and Bruggeman factor ([math] have been calculated by the nonlinear least square fit method. The intermolecular interactions between EGME-water binary mixtures suggest the nonlinear behavior of dielectric parameters. The contribution of hydrogen bonding interactions among the solute–solvent mixtures is confirmed by Excess properties and Bruggeman factor. Citation: Journal of Advanced Dielectrics PubDate: 2020-04-15T07:00:00Z DOI: 10.1142/S2010135X20500046

Authors:M. R. Hassan, M. T. Islam, M. N. I. Khan Abstract: Journal of Advanced Dielectrics, Ahead of Print. In this research, influence of adding Li2CO3 (at 0%, 2%, 4%, 6%) on electrical and magnetic properties of Ni[math]Mg[math]Fe2O4 (with 60% Ni and 40% Mg) ferrite has been studied. The samples are prepared by solid state reaction method and sintered at 1300∘C for 6[math]h. X-ray diffraction (XRD) patterns show the samples belong to single-phase cubic structure without any impurity phase. The magnetic properties (saturation magnetization and coercivity) of the samples have been investigated by VSM and found that the higher concentration of Li2CO3 reduces the hysteresis loss. DC resistivity increases with Li2CO3 contents whereas it decreases initially and then becomes constant at lower value with temperature which indicates that the studied samples are semiconductor. The dielectric dispersion occurs at a low-frequency regime and the loss peaks are formed in a higher frequency regime, which are due to the presence of resonance between applied frequency and hopping frequency of charge carriers. Notably, the loss peaks are shifted to the lower frequency with Li2CO3 additions. Citation: Journal of Advanced Dielectrics PubDate: 2020-04-14T07:00:00Z DOI: 10.1142/S2010135X20500034

Authors:Andryushina Inna, Pavlenko Anatoliy, Zinchenko Sergey, Andryushin Konstantin, Shilkina Lidiya, Glazunova Ekaterina, Nagaenko Alexandr, Stryukov Daniil, Sadykov Hizir, Reznichenko Larisa Abstract: Journal of Advanced Dielectrics, Ahead of Print. This paper presents the results of studies of the structure, microstructure, dependences of the piezoelectric properties on the electric field (dielectric hysteresis loops, reversible nonlinearity, deformation characteristics) and dielectric properties of the ceramic material PCR-13 (based on the PZT system) in the temperature range 300–900[math]K and frequencies of an alternating electric field ([math]) Hz. The character of the obtained dependences made it possible to attribute PCR-13 to ferro-hard materials. Using the HF cathodic sputtering method, PCR-13 thin films were fabricated on Si (001) substrates. It is shown that they are polycrystalline textured, while in comparison with bulk material, the film contains tensile stresses of the unit cell in the plane of the substrate and compresses in the perpendicular direction with the value [math]. The capacitance-voltage characteristics of the Al/PCR-13/Si/Al heterostructure were studied. The reasons for the revealed patterns are discussed. Citation: Journal of Advanced Dielectrics PubDate: 2020-04-14T07:00:00Z DOI: 10.1142/S2010135X20600036

Authors:Olga G. Maksimova, Oleg S. Piskunov, Roman A. Gerasimov, Olga S. Baruzdina, Andrew V. Maksimov Abstract: Journal of Advanced Dielectrics, Ahead of Print. In this work, shear strain modeling in materials consisting of a thin polymer layer ([math][math]nm), adhesive bonded to a rigid substrate, considered not to be impacted by deformation, was performed. A discrete-continuum model of chains system with a given stiffness with polar groups is developed. The polymer chain was considered in the framework of the persistene model, and the polar groups were based on the lattice model on the tetragonal lattice. It was assumed that the main contribution to the energy of interchain interactions is due to the potential of the polar groups and was calculated using the Metropolis algorithm. The potential interactions between the nearest polar groups of chains included the energy of dipole–dipole interactions (Keesom energy) and the Lennard–Jones potential. It is taken into account that the possible orientations of the polar groups are determined by the average elongation of the chain. Calculations showed that the dependence of free energy on the interchain distance has two minima. The first minimum is characterized by the orientational ordering of the polar groups, the second — by their disordered state. The depth and position of the minima depend on temperature, bending stiffness of the chain, the modulus of the dipole moment of the polar groups and the depth of the potential well in the Lennard–Jones energy. A step-by-step simulation of shear strain in a polymer layer in an orientationally disordered state was carried out. The obtained stress–strain diagrams make it possible to estimate the value of the elastic limit and also to determine the stresses at the points of phase transitions from a disordered to an orientationally ordered state. Citation: Journal of Advanced Dielectrics PubDate: 2020-03-25T07:00:00Z DOI: 10.1142/S2010135X20500022

Authors:Yu. V. Klunnikova, S. P. Malyukov, A. V. Filimonov, N. Zhang Abstract: Journal of Advanced Dielectrics, Ahead of Print. This research summarizes the analytical and experimental results of heat-transfer processes influence on defects formation during sapphire crystal growth by horizontal directed crystallization method (HDC). The shape of solid-melt interface significantly influences the process of sapphire crystals growth by this method. We receive the Stefan problem solution for sapphire crystals growth. It allows investigating the crystal growth process and the related factors (thermal stresses on different stages of growth process), their influence on defects formation. We investigate the main reasons for the formation of defective structures of the solid phase of sapphire crystals and the influence of thermal unit construction, the crystal geometry on the quality of the resulting sapphire crystal. We study the structure formation process, impurity distribution, and the nature of the defects in the crystal during it growth. Citation: Journal of Advanced Dielectrics PubDate: 2020-03-13T07:00:00Z DOI: 10.1142/S2010135X20600012

Authors:Haisheng Guo, Kexin Song, Zhenrong Li, Shiji Fan, Zhuo Xu Abstract: Journal of Advanced Dielectrics, Ahead of Print. Pb(In[math]Nb[math])O3-Pb(Mg[math]Nb[math]O3-PbTiO3 (PIN-PMN-PT) relaxor ferroelectric crystals in 5″ diameter by 5″ length were grown by the Bridgman (BR) method for the first time. Typical issues in the crystal growth concerning large volume of the melt, high density of the crystal and corrosion of the melt on the wall of Pt crucible are discussed. Citation: Journal of Advanced Dielectrics PubDate: 2020-02-28T08:00:00Z DOI: 10.1142/S2010135X20500010