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Specific mechanisms of grain structure effect on the thermoelectric properties (specific electrical resistivity and total thermal conductivity) of the Bi1.9Gd0.1Te3 compound have been analyzed. These mechanisms are as follows: 1) forming the surface Te vacancies at grain boundaries acting as donor centres; 2) changing the elemental composition of the grains at high-temperature Te evaporation under thermal treatment of material to prepare the samples with desired average grain size.

AgInSe2 nanopowders with a chalcopyrite structure and an average particle size of ~75 nm were synthesized from solutions by the polyol method of chemical synthesis. Spark plasma sintering was used to obtain bulk polycrystalline nanomaterials with an average grain size of ~110 nm. Electrons are the main current carriers in bulk materials. In the range 300–700 K, the features of the temperature dependences of the electrical resistivity, Seebeck coefficient, and total thermal conductivity of the nanomaterials are determined. It was found that the maximum thermoelectric figure of merit, equal to 0.1, is achieved at a temperature of 700 K.

Ceramic samples of the ternary 0.5Y0.1Zr0.9O2 − 0.5(0.6SrTiO3 − 0.4BiScO3) system consisting of the individual Y0.1Zr0.9O2 and 0.6SrTiO3 − 0.4BiScO3 subsystems were synthesized using solid-state pr...

Nanopowders of Bi2Te3 and R0.1Bi1.9Te3 (where R = Er, Tm, Yb, Lu) are obtained by microwave solvothermal synthesis. The powder-like materials are compacted by cold isostatic compression followed by annealing in argon. The influence of the doping agent on the structure and characteristics of the derived materials are investigated. It is demonstrated that the introduction of rare-earth elements (2 at %) into the bismuth-telluride lattice leads to a decrease in the electrical resistivity and to an increase in the Seebeck coefficient. The best thermoelectric properties are obtained for the sample of bismuth telluride doped with thulium.

Investigations of materials of the quasi-binary system Zn3As2–Mn3As2 have been performed. We present band structure calculations of crystal structures of Zn3As2, Mn3As2 and ZnMn2As2 within the framework of the density functional theory (DFT) and DFT + U method. The calculations based on first-principles were made using plane waves normalized on pseudopotential with the Quantum Espresso software package. Was obtained, that fundamental gap for Mn3As2 and Zn3As2 is equal to the optical band gap, while the band gaps for ZnMn2As2 was closer. The calculation for Mn3As2 and ZnMn2As2 by method DFT + U were performed; in these cases, the fundamental band gaps are closer to the optical band gaps, respectively. Considering the series Zn3As2 → ZnMn2As2 → Mn3As2, an increase in the Fermi energy was observed: Ef = 7.5 → 8.98 → 12.04 eV. It was established that the band gap of ZnMn2As2 (Eg = 0.6 eV) is a direct band gap corresponding to the transition between points Γ→Γ of the Brillouin zone. The Eg value obtained by us is closely known from experiments on optical absorption and the study of the temperature dependence of resistivity with Eg values equal to 0.8 eV and 0.76 eV, respectively. For Mn3As2 and ZnMn2As2, splitting is observed in density of states (DOS) between spin up and spin down electrons.

Single phase and nanosized powders of high-entropy (BiSbSe1.5Te1.5)1-x Cu x compound with x=0; 0.3, 0.6 were synthesized by using soft chemistry approaches. Owing to its low thermal conductivity, this compound is promising for thermoelectric applications. The synthesized powders were used to prepare bulk samples totally suitable for testing thermoelectric properties.

A three-component ceramic material is obtained in the system ZrO2–SrTiO3–BiScO3; its phase composition and microstructure particularities are determined; and, the temperature dependence of the conductivity is studied. It is found that at room temperature the material consists of a cubic phase with space symmetry group Fm3m, corresponding to the cubic modification of zirconium dioxide, and a solid solution consisting of nonpolar cubic phase with Pm3m symmetry and polar tetragonal phase with P4mm symmetry characteristic for a two-component SrTiO3–BiScO3. An investigation of the microstructure and elemental composition of samples by means of scanning electron microscopy confirms the presence of these phases. It is found that above the temperature about 750 K the conductivity of the experimental samples increases significantly.

Charge carriers parameters on a 2D-layer surface for (Cd1−x−yZnxMny)3As2 (y = 0.08) (the concentration n 2 D = 1.9 × 1012 cm–2, the effective value of the 2D-layer d 2 D = n 2 D / n 3 D = 14.5 nm, the wave vector k F = 0.1 nm–1, the charge carriers relaxation time due to dispersion τ D = 1.8 × 10–13 s, the velocity of charge carriers on Fermi surface v F = ℏ k F / m c = 2.65 × 105 m s−1, the mean free path l F = v F τ D = 47.7 nm) were determined. It was found that the dependence of the cyclotron mass m с (0)/m0 on Fermi wave vector k F for (Cd1−x−yZnxMny)3As2 (y = 0.08) is in compliance with a theoretical linear dependence, that describes mass-less Dirac fermions.

Elastic and anelastic properties of the relaxor 0.55SrTiO3-0.45BiScO3 ceramics were studied. Anomalous behavior of the Young's modulus and the internal friction were observed at cooling below the Burns temperature Td ≈585 K. Both elastic and anelastic anomalies were found to be frequency dependent. Elastic softening is assumed to be due to an electrostriction relationship between spontaneous polarization of polar tetragonal nanoclusters and a strain of unit cell. It was found that the internal friction anomaly observed below Td is in fact superposition of two maxima. Higher temperature maximum is typical for relaxors. Using the special internal friction mechanism for the first order phase transition, the size of the polar tetragonal nanoclusters was estimated to be equal to ∼10 nm. Such sizes of tetragonal islands were found for the sample under study by using the electron backscattered diffraction method.

A general method of adaptation of pixel-by-pixel background subtraction models designed for a fixed camera is developed in the case of a PTZ camera mounted on a mobile platform. The method involves the use of two identical pixellevel background models. The first one is directly applied to the classification of the current scene, while the second one is used to prepare the first model for the transformation to the new coordinate system, the one closer to the current position of the PTZ video camera. The chosen solution makes it possible to eliminate a large number of false positives, which inevitably occur after each transformation of the background model. The experimental verification of the developed method using two well-known background models GMM and ViBe demonstrated good quality of the scene classification and low computational load.

Single crystalline Eu3+-doped wurtzite ZnO micro- and nanowires were synthesized by a chemical vapor deposition method (CVD). The nanostructures were grown by autocatalytic mechanism at walls of an alumina boat. The structure and properties of the doped ZnO is fully characterized by X-ray diffraction (XRD), energy-dispersive X-ray spectrometry (EDX), scanning and transmission electron microscopy (SEM and TEM), and photoluminescence (PL) methods. The synthesis was carried out for 10 min giving vertically aligned nanowires with mean diameter of 50–400 nm and with length of up to several microns. The nanowires were grown along ±[0001] direction. The concentration of Eu3+ dopant in the synthesized nanowires was varied from 0.7 to 0.9 at %. The crystal structure and microstructures of the doped nanomaterials were discussed and compared with undoped ZnO. The photoluminescence spectra show that emission of doped samples were shifted towards orange-red region (2.02 eV) relative to undoped zinc oxide nanostructures (2.37 eV) due to Eu3+ intraionic transitions from ZnO/Eu.

Elastic properties of the ceramic 0.7SrTiO3-0.3BiScO3 sample with relaxor ferroelectric properties were studied in the vicinity of the Burns temperature Td = 550 К. It was found that for the sample under study an anomalous decreasing of the Young's modulus takes place just below the temperature Td. This elastic softening is assumed to be due to electrostriction relationship between spontaneous polarization of polar nanoclusters and strain of the sample.

Dielectric anomalies specific for relaxor ferroelectrics have been found for the SrTiO3-BiScO3 system. The relaxor properties of this system are rather unexpected because neither SrTiO3 nor BiScO3 are ferroelectrics. An X-ray diffraction analysis revealed that at room temperature the ceramic (1-x)SrTiO3-xBiScO3 samples with x = 0.2, 0.3 and 0.4 consist of a mixture of a cubic centrosymmetric Pm3m phase and a tetragonal polar P4mm phase. Lattice parameters for these phases increase as x increases. In addition, it was found by the electron backscattered diffraction method that at room temperature, the fraction of the cubic phase decreases and the fraction of the tetragonal phase increases as the mole fraction of BiScO3 increases. Phase coexistence is assumed to be one of the reasons for the relaxor properties of the system under study.

Температурна залежність питомого електричного опору ρ Bi1.9Lu0.1Te3 вивчено в інтервалі температур 2 ÷ 230 K. Мінімум опору виявлений при температурі Tm ≈ 11 K. Цей мінімум з'являється через зміну механізму провідності. Вище Tm опір збільшується зі збільшенням температури. Це поведінка зумовлена зменшенням рухливості електронів через розсіювання фононів при нагріванні. Нижче Tm стрибкова провідність з змінної довжиною стрибка, заснована на тунелюванні електронів, має місце. В цьому випадку ρ збільльшується зі зменшенням температури. Два польових режима стрибкової провідності виявлені в залежностях опору від напруженості електричного поля. Температурная зависимость удельного электрического сопротивления ρ Bi1.9Lu0.1Te3 изучено в интервале температур 2 ÷ 230 K. Минимум сопротивления обнаружен при температуре Tm ≈ 11 K. Этот минимум появляется из-за изменения механизма проводимости. Выше Tm сопротивление увеличивается с увеличением температуры. Это поведение обусловлено уменьшением подвижности электронов из-за рассеяния фононов при нагревании. Ниже Tm прыжковая проводимость с переменной длиной прыжка, основанная на туннелировании электронов, имеет место. В этом случае ρ увеличивается с понижением температуры. Два полевых режима прыжковой проводимости обнаружены в зависимостях сопротивления от напряженности электрического поля. The temperature dependence of the specific electrical resistivity, ρ, of the Bi1.9Lu0.1Te3 alloy has been studied within the temperature 2 ÷ 230 K interval. Minimum in the resistivity was found at temperature Tm ≈ 11 K. This minimum is originated from a change of conductivity mechanism. Above Tm, the resistivity ρ increases as temperature increases. This behavior is due to the electron mobility decrease via an acoustic phonon scattering at heating. Below Tm, the variable-range hopping conductivity based on electron tunneling takes place. In this case, ρ increases as temperature decreases. Two electric field regimes of the hopping conductivity were observed in the resistivity versus electric field strength dependences.

Positive nonsaturating transverse magnetoresistivity (MR) has been observed below room temperature in the Bi1.9Lu0.1Te3 alloy with inhomogeneous micrograined structure. A crossover from parabolic MR ~ B2 dependence in low magnetic fields to linear MR ~ B dependence in high fields was found in the magnetoresistivity curves. The crossover field is shifted to lower magnetic fields as temperature decreases. Within the temperature range of “metal” type of conductivity, the temperature dependences of the specific electrical resistivity and MR magnitude are determined by the temperature dependence of the carrier mobility due to acoustic phonon scattering. Linear MR can be associated with microstructural inhomogeneity leading to strong electrical disorder of the Bi1.9Lu0.1Te3.

The influence of the creeping discharge on the air flow in the boundary layer and the adjoining region of a plate with a cylindrical wedge has been investigated experimentally. Experiments were carried out in a supersonic wind tunnel at a Mach number M = 3.0. The processes of initiation and propagation of such a discharge and boundary layer development on the above objects under the action of this discharge have been investigated. The data on the flow around a wedge-shape projection on the plate are presented.

The properties of coatings manufactured from titanium powder are described in this study. Coatings with thicknesses of 100 and 200 μm were deposited on a steel substrate using cumulative-detonation technology. The investigations showed the low porosity of the coatings and the absence of defects at the boundary with the substrate. Scratch tests of the coatings fixed their high adhesion and cohesion properties. Corrosion tests showed that the protective properties of the coatings are fairly high in NaCl and low in HCL. Increasing the thickness of the coatings to 0.2 mm strengthens their protective properties. Nanodispersion compounds of titanium with iron, oxygen, and carbon that decrease the corrosion resistance of the specimens in the chlorohydric acid were detected in the coatings.

Effects of polarization of hadrons and constituent quarks in Drell-Yan processes are considered; they are one of the most efficient tools for investigation of the quark structure of hadrons. Special attention is paid to such important parton distribution functions as the transversity and T-odd Sivers and Boer—Mulders functions whose study is necessary for understanding the effects connected with the nonzero transverse component of the quark momentum. An original method for direct extraction of transversity and Boer—Mulders function in the proton from the data on Drell—Yan processes, in which a maximum of one hadron in the initial state is transversely polarized, is presented. This method possesses a number of important advantages. The method is applied both to Drell—Yan processes with a valence antiquark (antiproton-proton and pion-proton collisions) and with a sea antiquark (proton-proton, proton-deuteron, and deuteron-deuteron collisions). Theoretical estimates of asymmetries and cross sections for setups at RHIC (BNL, US), NICA (JINR, Russia), COMPASS (CERN, Switzerland), PAX (GSI, Germany), and J-PARC (Japan) are presented for evaluation of the measurability of transversity and T-odd distributions. These theoretical estimates are accompanied by calculations of statistical uncertainties for measured asymmetries using the new Monte Carlo generator of Drell—Yan events. The duality of Drell—Yan processes and those of production of J/Φ resonance is studied, and it may allow one to considerably reduce statistical uncertainties of parton distributions. Kinematical conditions, for which this duality can be observed, are evaluated.

A detailed review of the current state of investigations into polarized deep inelastic scattering (DIS) is presented. Special attention is given to the methods of the QCD analysis of experimental data on these processes and to the methods of extrapolation of polarized structure functions and polarized quark distributions in the regions inaccessible to current experiments. In the case of pure inclusive processes, the QCD analysis of all worldwide data, including the latest COMPASS data, is presented in detail. Special attention is given to such important components of the nucleon-spin problem as the polarized strangeness and polarized gluon distribution. The features of SIDIS processes are considered; in particular, the role of fragmentation functions in the analysis of the semi-inclusive data is discussed. The methods of extracting the fragmentation functions from experimental data are considered in detail, and the corresponding results are presented. The results of analysis of the existing semi-inclusive polarized data both in the QCD leading order and in the next-to-leading order are considered. Special attention is given to non-standard, so-called difference asymmetries, which make it possible to minimize the dependence of results of analysis on the fragmentation functions. The current methods of QCD analysis of semi-inclusive polarized data are critically reviewed. An alternative method of QCD analysis of semi-inclusive data is presented for next-to-leading order QCD. Advantages of the method in practical applications are illustrated by the example of analysis of the HERMES data.

Using an inverted torsion pendulum, the peculiarities of low-frequency shear elastic and anelastic properties of the ferroelastic crystals Ba 2 NaNb 5 O 15 and K 2 Ba(NO 2 ) 4 have been investigated for various crystallographic oriented samples at temperature variation in the vicinity of their phase transition points. The work gives insight into the nature of the spontaneous shear strain behavior and spontaneous torque arising in the samples at the Curie point.

Using a torsion pendulum, the peculiarities of low-frequency shear elastic and anelastic properties of the improper ferroelastic crystal K2Ba(NO2)4 have been investigated for various crystallographic oriented samples at a temperature range in the vicinity of the phase transition point (TC = 420 K). The work gives insights into the nature of the internal friction and spontaneous torque arising in the samples at the Curie point.

Spontaneous twisting of (NH4)2SO4 crystals at the phase transition from the paraelectric phase Pnam to the ferroelectric phase Pna2 (TC = 223 K) was studied using the method of low-frequency torsion pendulum. It is shown that the macroscopic twisting of samples is caused by the rearrangement of ferroelastic twins with the {011} and {031} twinning planes existing in both the paraelectric and ferroelectric phases. A model interpreting the effect of the spontaneous twisting below the ferroelectric Curie point is proposed.

Low-frequency elastic and anelastic properties of the ceramic PbFe0.5Nb0.5O3 were investigated by the inverted torsion pendulum in the temperature range including the Neel (TN) and Curie (TC) temperatures. The shear modulus and the internal friction anomalies observed in the vicinity of TN are due to magnetostriction connection between a strain and magnetic spin ordering. The electric field effect on elasticity of the sample in the vicinity of TC was found.

Anomalous behavior of the low-frequency elastic and anelastic properties of the ceramic PbMg1/3Nb2/3O3 was found by the inverted torsion pendulum within the temperature range corresponding to the diffused phase transition. This transition was also observed via dielectric measurements, which allowed finding the dielectric constant anomaly of the relaxor type.

Low-frequency elastic and anelastic properties of the ceramic PbFe0.5Nb0.5O3 were investigated by the inverted torsion pendulum in the temperature ranges including the Curie and Neel temperatures. Correlation between elastic and dielectric properties was found to take place within the diffuse ferroelectric phase transition. The shear modulus and the internal friction anomalies observed in the vicinity of TN are due to magnetostriction connection between a strain and magnetic spin ordering.

The internal friction and shear modulus of a barium sodium niobate crystal were studied using the torsion pendulum technique at a frequency of ∼25 Hz in the temperature range from 80 to 800 K. An internal friction relaxation peak of the domain nature was observed at 228 K. A relaxation process responsible for this internal friction peak is explained through compensation of the electric charge (induced by a piezoelectric effect at the 180° domain walls) by charged point defects diffusing toward the domain walls.

It is found that the ferroelectric phase transition in the ammonium sulphate crystal (NH4)2SO4 at TC=223 K is accompanied by spontaneous twisting of samples around the a, b, and c crystallographic axes in the ferroelectric phase. This twisting, observed with a torsion pendulum, cannot be explained solely by the change in symmetry mmm → mm2 at the Curie point. It is supposed that the twisting is connected with a complex rearrangement of the structural elements of the crystalline lattice below the Curie temperature.

The possibility of using silicon-containing mineral raw material (quartz sand and sandy opoka) mined in the Belgorod region for manufacturing ceramic materials with a combination of high thermostability and satisfactory mechanical compressive strength was demonstrated.

An amorphous Ni alloy has been obtained as a ribbon by plasma-arc melt spinning in a copper water-cooled lining slag crucible. Ribbon samples have been annealed in a special cylindrical furnace at temperatures from 200 to 400°C for 1 h in Ar. It is established that nanocrystals in the alloy samples increase in size with increasing annealing temperature. The rise of resistivity upon annealing at temperatures below 300°C and its significant decrease at higher temperatures is consistent with the change in the amorphous alloy microstructure.

A correlation between the behaviour of the anelastic properties and the evolution of the misfit parameter in incommensurate barium sodium niobate was found. The internal friction peak was observed near the 1-q → 2-q transition within the incommensurate phase, accompanied by a drastic change of the ferroelastic domain structure.

The peculiarities of low-frequency internal friction near the first order low-temperature (110 K) and second order high-temperature (573 K) phase transitions in improper Ba2NaNb5O15 ferroelastic were studied. A large and wide internal friction peak and diffused step-like change in the temperature dependence of shear modulus were also observed within an incommensurate phase between these two phase transitions.

Peculiarities in the behavior of the dielectric, elastic, and anelastic properties of the PbFe1/2Nb1/2O3 ceramic ferroelectromagnet have been found and investigated near the antiferromagnetic phase transition (Neel temperature T N = 160 K). It is established that the transition to the antiferromagnetic phase leads to a decrease in the permittivity and elastic compliance. The anomaly of permittivity found near T N indicates the presence of magnetoelectric interaction in the magnetically ordered phase.

The anomalous changes of the low-frequency elastic and inelastic properties of single-crystal (NH4)2SO4 accompanying the phase transition from the paraelectric to the ferroelectric phase have been studied by the reverse torsion-pendulum method at 223 K and in the temperature region where the spontaneous polarization changes sign.

The comparative investigation of low (110K) and high-temperature (573 K) ferroelastic phase transitions in Ba2NaNb5O15 crystal was carried out by low-frequency inverted torsion pendulum. The anomalies of elastic and anelastic properties, corresponding to the phase transitions are differed essentially. A large and a wide internal friction peak was also observed at 228 K. A possible nature of mechanical loss is discussed in frame of domain wall dynamics in a crystal with defects.

The dielectric, elastic, and inelastic properties of a ceramic ferroelectric SrBi3Nb2FeO12 are studied over the temperature range 300–900 K. The observed anomalies in the temperature dependences of the permitivity, dielectric loss, shear modulus, and internal friction indicate the occurrence of a structural phase transition in the compound at ∼700 K. It is suggested that the transition is a proper ferroelectric and improper ferroelastic second-order phase transition.

Composite coatings of titanium powder were deposited on aluminium samples by using the cumulative-detonation equipment. Consumption of fuel mixture components (propane-oxygen-air) was up to 4.3 m3 per kilo of a coating. The coatings were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM) with diffraction, X-ray phase analysis, hardness measurements, as well as plasticity and adhesion/cohesion resistance scratch tests. It is shown that the coatings are characterised by the presence of nanodispersed ceramic formations, and feature high values of plasticity, hardness and adhesion strength.

Low-frequency (10-20 Hz) internal friction and shear modulus of superconducting YBa2Cu3O7-δ (δ = 0.1) ceramics have been studied at a temperature range from 40 to 1000 K. It is shown that in many cases the internal friction peculiarities were due to dynamics of ferroelastic twins.

The influence of twin structure state on the mechanical (elastic and anelastic) properties of high-temperature superconducting YBa2Cu3O7-δ ceramics and transition temperature Tc into the superconducting phase has been studied.

A comparison study of the infralow-frequency shear modulus G and internal friction Q−1 of nonsuperconducting La2 CuO4 and high-temperature superconducting La1·85Sr0·15CuO4 has been made in the temperature range 20 to 650 K.

La transition de phase tetragonale-orthorhombique de ce supraconducteur est ferroelastique et du premier ordre. Dans la phase ferroelastique, les proprietes elastique et anelastique dependent fortement de l'etat de structure du domaine et de la mobilite des macles elastiques dans un cristal reel

The spontaneous twisting of a y-orientation single-crystal sample of barium-sodium niobate Ba2NaNb5O15 at a phase transition and into an incommensurable ferroelastic phase is investigated. Anomalies are found in the temperature dependence of the torsional deformation at temperatures 453, 533, and 573 K and anomalous hysteresis of the temperature dependences of the torsional deformation, measured on heating and cooling of the sample. The results obtained are discussed on the basis of an analysis of the temperature dependence of incommensurable 1q and 2q structures and ferroelastic twins.

It is shown that at infralow frequencies near the ferroelastic phase transition point of YBa2Cu3O7-6 ceramics fluctuation mechanism responsible for the internal friction takes place and that tetragonal-orthorhombic phase transition is the first-order one.

The results of an experimental investigation of various methods of influencing the flow in the near wake by injecting a system of jets and varying the rear-end configuration for a Mach number M=3 are presented. The structure of the base flow and the pressure fluctuations behind an axisymmetric body with a base cavity when circular and annular gas jets are injected is investigated. The results are compared with the data for bodies with a flat base.