Based on the data of thermogravimetric analysis the values of the oxygen index (3–δ) in the manganite of the La_0.7Sr_0.3Mn_0.9Fe_0.1O_3-δ composition, obtained by solid-phase reaction technique, have been calculated. The analysis of oxygen sorption-desorption curves showed that the processes of oxygen release and absorption at pO₂ = 10 Pa and pO₂ = 400 Pa are not reversible. The minima of the derivative dδ/dt = f(T) corresponding to the maxima of the oxygen extraction rate indicate the complex character of changes in the oxygen desorption rate from manganite. The decrease in the heating and cooling rate from 6.6 to 2.6 K/min resulted in a significant change in the value ∆δ, indicating the dependence of anion mobility on the oxygen concentration in the magnet structure. It has been revealed that in the La_0.7Sr_0.3Mn_0.9Fe_0.1O_3-δ manganite the oxygen desorption kinetics is well described by the exponential dependence on the Cramers model, which implies no return of desorbed oxygen to the sample. This model indicates the non-stationarity of the diffusion flux through the barrier during desorption of oxygen from samples. The calculation of the activation energy of oxygen desorption by the Merzhanov method at various partial pressures of oxygen has shown that at the initial stage of oxygen extraction from La_0.7Sr_0.3Mn_0.9Fe_0.1O_3-δ, the activation energy of oxygen desorption has a minimum value (Е_а = 103.7 kJ/mol at δ = 0.005) and as the concentration of oxygen vacancies increases, it rises reaching saturation (Е_а = 134.3 kJ/mol at δ = 0.06). It is assumed that with an increase in the concentration of oxygen vacancies, an interaction occurs between them, followed by the processes of their ordering with the formation of associates.

Problems of the synthesis of cadmium telluride powders having required purity and grain size distribution for high-efficiency solar cells have been analyzed. A test batch of powders has been synthesized and used for the manufacture and study of thin-film solar cell specimens exhibiting parameters compliant with the best worldwide standards. The phase composition of the powders has been studied using X-ray diffraction. Structural analysis and elemental composition measurements have been carried out using electron microscopy. The effect of free tellurium phase in the powders on the endurance of devices manufactured from the powder has been described. We show that excess tellurium in the film specimens whose atoms are predominantly localized along grain boundaries may cause temporal degradation of the electrical properties of the manufactured solar cells due to changes in the parameters of the crystalline structure of the cadmium telluride phase which are caused in turn by changes in the stoichiometric composition of the material. Structural studies of the film specimens have not revealed differences in the film structure before and after endurance tests. A new cadmium telluride powder process route has been developed, proven and tested taking into account the advantages and drawbacks of the previously used process and experiments confirming the correctness of the technical solutions chosen have been conducted.

In this work the effect of annealing in a constant magnetic field on the magnetoelectric (ME) coefficient in three-layered gradient composites<LiNbO₃/Ni/Metglas> is investigated. A technique of nickel electrochemical deposition on bidomain lithium niobate crystals was demonstrated. It is shown that the optimum temperature for the formation of the maximum remanent magnetization of the Ni layer in a constant magnetic field is 350 °C. In the samples annealed at this temperature, the maximum shift of the dependence of the ME coefficient on the external constant magnetic field relative to the value of 0 Oe was achieved. Quasistatic ME coefficient value was 1.2 V/(cm∙Oe) without applying of external DC magnetic field. The maximum value of the ME coefficient was reached 199.3 V/(cm∙Oe) at bending resonance of 278 Hz without external DC magnetic field. Obtained in this work values of ME coefficients don’t yield to most of ME composite materials which were published before.

The calculation of conductivity electron concentrations in n-GaSb at T = 295 K and T = 77 K have been made. The concentration of “heavy” electrons in the L-valley of conduction band at Т = 295 K has been shown to exceed “light” electron one in the Γ-valley. On the contrary, at T = 77 K the conductivity electrons are gathered in the Γ-valley.
The results of Hall measurements made on tellurium-doped samples of n-GaSb obtained by the Czochralski method have been represented. It has been shown that upon analysing Hall data at Т = 295 K, it is necessary to take into account the presence of two types of electrons (“light” and “heavy”); their concentrations are not possible to be determined. Seeming increase in electron concentration upon transition from T = 295 K to 77 K really does not take place. The electron concentration at T = 77 K may be determined correctly from the Hall data.

The results of substantiation of the improved technology for manufacturing of the frequency-selective electromagnetic shields are presented. The improvement of this technology was ensured by the following: 1) the inclusion of elements in the form of classical Archimedes spirals, formed from foil materials, into the volume of manufactured shields to ensure the frequency-selective properties of such shields; 2) fixing the specified elements in the volume of manufactured shields by thermal pressing. The indicated features determine the main advantage of the improved technology in comparison with its analogues — lower time costs required for its implementation. The substantiation of the improved technology was implemented in the following areas: 1) setting the parameters of Spiral elements, which correspond to the maximum values of energy losses of the electromagnetic radiation interacting with them in the microwave range; 2) determination of the order of arrangement of spiral elements in the volume of the screens, which corresponds to the lowest values of electromagnetic radiation transmission and reflection coefficients in the microwave range of these shields. The substantiation implemented in the first of the indicated directions was based on the results of the analysis of the content of scientific works devoted to mathematical modeling and the study of the electromagnetic radiation of the transmission characteristics of flat spiral antennas in the microwave range. The substantiation implemented in the second of the indicated directions was based on the manufacture of experimental samples of the shields, the volume of which includes spiral elements oriented in a certain way, and further obtaining and comparative analysis of electromagnetic radiation transmission and reflection characteristics in the microwave range of these shields. Shields manufactured in accordance with substantiated improved technology seem to be promising for use in order to protect electronic devices from the effects of electromagnetic interference.

Since the early 1980s, the terahertz range (from 0.1 to 10 THz) attracts constant attention of both fundamental and applied physics. Due to its unique properties, terahertz radiation finds it’s applications in spectroscopy, defectoscopy, and security systems. The construction of efficient absorbers and converters in terahertz range is crucial for further development of terahertz technologies. In this work, we use a frequency-selective high-Q metamaterial to construct a converter of terahertz radiation into the infrared radiation. The converter consists of a metamaterial absorber of terahertz radiation covered with a micrometer thick layer of graphite, which emits in the infrared range the energy absorbed by the metamaterial. We have made a numerical electrodynamic and associated thermal simulation of the radiation converter. The metamaterial simulation at 96 GHz (low opacity window of the atmosphere) shows the electromagnetic radiation absorption coefficient of 99.998%, and the analytically calculated converter efficiency of 93.8%. Concluding the above our terahertz radiation converter may contribute to security systems and defectoscopy setups.

Monocrystalline calcium molybdenum CaMoO₄ is a well-known material. Recently, there has been a surge of interest in CaMoO₄ due to a number of popular applications, such as working medium for a cryogenic scintillation bolometer. During growth CaMoO₄ single crystals acquire a blue color due to the presence of defective centers, such as color centers, which is unacceptable for optical applications. To eliminate the coloration, annealing in an oxygen-containing atmosphere is used and then the necessary elements are prepared from the crystals by mechanical influences (cutting, polishing, etc.). In this regard, for the rational solution of issues arising in the manufacture of products from these crystals and their further practical use, the assessment of the mechanical properties of these crystalline materials is an urgent task. However, the results of studies of the mechanical properties of CaMoO₄ are poorly presented, without taking into account anisotropy; there is a significant spread of data on the value of hardness by Mohs. For different authors, hardness varies from 3.5 to 6. In this paper, samples of single crystals of calcium molybdate in the initial state and after high-temperature annealing of different duration in an oxygen-containing atmosphere are studied. It is shown that prolonged annealing leads to discoloration of crystals. It has been established that calcium molybdate crystals are extremely brittle, the brittleness score of Zp crystals in the initial state is maximum and is 5, annealing leads to a decrease in the brittleness score to 4. The “viscosity” parameters are calculated by the Palmqvist S method. The nubs of complete destruction of F_pr prints were established, it was shown that annealing in an oxygen-containing atmosphere leads to an increase in F_pr by 2.5 times for the Z-cut, by 10 times for the X-cut. It is shown that the microhardness of crystals is characterized by anisotropy of the II kind: for all samples, the microhardness of the Z-cut is higher than the microhardness of the X-cut. The anisotropy coefficients of the microhardness of the KH samples are estimated. On the basis of the measured values of microhardness, the degrees of ionic bonds I are calculated.

Aluminum in terms of electrical conductivity among all known metals ranks fourth after silver, copper and gold. The electrical conductivity of annealed aluminum is approximately 62% IACS of the electrical conductivity of annealed standard copper, which at 20 °C. is taken as 100% IACS. However, due to its low specific gravity, aluminum has a conductivity per unit mass 2 times greater than copper. This property of aluminum gives us an idea of the economic viability of using it as a material for conductors. With equal conductivity (the same length), the aluminum conductor has a cross-sectional area 60% larger than copper, and its mass is only 48% of the mass of copper. In most cases, in electrical engineering, the use of aluminum as a conductor is difficult, and often simply impossible due to its low mechanical strength. An increase in the mechanical strength of aluminum is possible due to the introduction of alloying additives, i.e. creating alloys. In such a case, the mechanical strength increases, causing a noticeable decrease in electrical conductivity. The heat capacity of the aluminum conductor alloy AlTi0.1 (Al + 0.1 wt.% Ti) with calcium in the “cooling” mode was determined from the known heat capacity of the standard aluminum sample. Equations are obtained that describe the cooling rates of specimens made from an aluminum conductor alloy AlTi0.1 with calcium and a reference. Based on the calculated values of the cooling rates of the samples, the equations for the temperature dependence of the heat capacities of the alloys and the standard were formed. The temperature dependences of changes in enthalpy, entropy, and Gibbs energy for the aluminum alloy AlTi0.1 with calcium are calculated by integrating the specific heat capacity. The heat capacity, enthalpy, and entropy of the AlTi0.1 alloy decrease with increasing calcium concentration, and increase with increasing temperature, while the value of the Gibbs energy has an inverse relationship.