[en] It is shown that the unique features of the physical properties of rare-earth semiconductor compounds are based on the small values of the ionization potentials of the rare-earth elements included in them. The reason for this is the presence of 4f shells in the electronic structure of the elements.

[en] The effect of cyclic loading on the magnitude of coherent scattering regions (CSR) of X-ray radiation and microstresses of the II type in various crystalline materials: semiconductor (samarium sulfide) and metal (steel, duralumin) has been found. The loading was carried out by compressing the samples in various ways: all-round, uniaxial, bending compression. It is shown that with an increase in the number of compression cycles, the CSR values in all cases decrease, and the microstresses increase. These values can serve as parameters to assess the degree of mechanical fatigue of the material.

[en] The influence of doping of samarium monosulfide with gadolinium has been investigated. Experiments have been carried out in the temperature range of 300–450 K. A decrease in the effect value with increasing gadolinium content in the Sm1–xGdxS heterostructure with x ranged from 0 to 0.13 has been found and explained. Formulas for calculating the output signal in dependence of the doping value have been derived.

[en] The far- and mid-IR reflection spectra of Sm_{1+ x}S (x = 0–0.17) samples are recorded and analyzed, as well as their electrical and structural parameters at a temperature of T = 300 K. The bond ionicity in SmS is shown to fall with a decrease in the area of the X-ray coherent scattering region and an increase in the concentration of donor impurities and, consequently, conduction electron concentration. The electrical conductivity of stoichiometric SmS single crystals and polycrystals can be determined with an error of 10% from the IR reflection spectra. Due to the low structural quality of the samples, the electrical conductivity cannot be determined in the case of deviation from stoichiometry.

[en] Young’s modulus and the logarithmic decrement of oscillations at a frequency of ~100 kHz as well as the subgrain size and residual stresses in the strontium modified alloy of aluminum with 15 wt % silicon have been studied. The alloy was obtained with a solidification rate of 1 mm/s at the shifted eutectic point. The dependence of inelastic dislocation deformation on the applied oscillating stress has been obtained and analyzed. The effect of strontium modification on the microstrain diagram can be accounted for by transformation of the lamellar fiber structure of eutectic silicon into a superfine fiber structure.

[en] Electrical properties of thin SmS polycrystalline films with various values of the lattice constant at T = 300-580 K are studied. Specific features of the temperature dependences of electrical conductivity at T > 450 K are revealed. The effect of generation of the electromotive force with magnitude as large as 1.3 V at T = 440-470 K is observed when the films were subjected to the pressure of a spherical indenter. It is shown that it is possible to transform SmS films into a high-resistivity state (with the difference in the resistivity by three orders of magnitude) by applying an electric field with the strength higher than 100 V/cm. All the results obtained are accounted for using a model of the phenomenon of the electromotive-force generation in SmS under uniform heating of the sample and can also be attributed to the variable valence of samarium ions with respect to the lattice defects

[en] The electrical parameters of polycrystalline Sm_1_–_xEu_xS compounds are studied. The conductivity, concentration of free electrons, their mobility, and the conductivity activation energy are measured as functions of the quantity x. The structural parameters of the compounds are determined. A heterostructure is fabricated with x in the range from 0 to 0.3, and the electrical voltage generated by the structure, when heated to a temperature of T = 450 K, due to the thermovoltaic effect is measured. This voltage is found to be 55 mV. A method for measuring the thermally induced voltage is described. The method provides a means for separating the thermovoltaic effect from the Seebeck effect.

[en] The rare-earth semiconductor β-Ce₂S₃ compound samples were synthesized and their dielectric permittivity and electrical conductivity were measured in the temperature range 90–400 K. The energy-band structure has been determined. It is shown that the long-known large electrical parameter spread of semiconductor compounds close in composition to Ce₂S₃ is explained by the structure of impurity donor levels formed by cerium atoms and ions with different ionization degrees.

[en] The developed method of semiconductor gas Fourier spectroscopy is based on the relationship of the obtained calibration characteristics of the concentration sensors for volatile hydrocarbons contained in atmospheric air (in our case, it is methane and propane), with electrophysical parameters of the gas sensitive layers. The study used gas sensors based on samarium sulfide with reproducible and stable calibration characteristics. The working layers of hydrocarbon concentration sensors were obtained by two different methods: the explosive spraying method and the sol-gel coating technology. In this paper we present a system of equations that includes the main electrophysical characteristics of a gas-sensitive film which is solved by numerical methods. These equations reflect a unique relationship between the Debye screening length (L_d), film thickness (d), Fermi level (E_F), concentration of impurity levels (N_d), dielectric constant of the medium (ε), crystal lattice constant (a), and mobility of the main charge carriers (μ) with the observed data on the change in the conductivity of thin films of samarium sulfide in the processes of adsorption of methane and propane molecules on their surface. In the present work, we obtained the first calculated data of such parameters for the current prototype images of gas sensors of methane and propane. (paper)

[en] The magnetic properties (field range H = 0–50 kOe, temperature range T = 3–300 K), and structural features of a sodium-doped carbon composite material based on fullerene C₆₀ and thermally exfoliated graphite (TEG) are studied. The material is obtained with different ratios of the components by sintering at a pressure of 7 GPa and T = 600°C, at which it is found that significant amorphization of the crystal lattice of the initial C₆₀ occurs. The dia-, para-, and ferromagnetic components (M_D, M_PM, and M_FM) were separated from the total magnetic moment of the samples under study. It is found that a sodium dopant has no effect on the magnetic properties of the composite. Analysis of the M_PM(H) field dependences by using the Brillouin function for the fullerene-containing sample (i.e., without TEG) makes it possible to determine the quantum number of the total angular momentum of paramagnetic (PM) centers. Its value is found to be J = 1, which corresponds to elementary magnetic moment μ_PM = 2μ_B of a PM center. The concentration of PM centers is estimated at the level of N_PM ≈ (2–5) × 10¹⁸ g^–1 for most samples, including the material without TEG. The introduction of TEG into the initial composition and an increase in its proportion in the composite leads to a strong increase in the magnetic moment, which is explained by an increase in both the J value and the concentration of PM centers.