The paper discusses the possibility of increasing the transition temperature of metal-oxide compounds ("high-temperature" superconductors) to the superconducting state (zero electrical resistance) when irradiating them with a sufficiently powerful photon flow. In this case, in the irradiated substance, as a result of internal photo-ionization, changes occur in both the important parameters of the phonon spectrum and the electrons energy spectrum. The value of the photon energy must satisfy this condition: hν ≥ W (ν is the photon frequency, W is the energy of the photoinduced chemical reaction. According to the estimates made in the work, the minimum wavelength of photons that can realize the described effect should be characterized by the value l≈10–4m. Photons of this wavelength correspond to infrared light radiation, a flow of sufficient power of which is easily achieved by laser technology. A change in the parameters of the phonon spectrum and the energy state of electrons in the discussed compounds when they are irradiated with photons causes the formation of an additional number of clusters of special ion complexes (negative U-centers), which are capable of generating quasiparticles: "Cooper" pairs of electrons (bosons). The formation of clusters of negative U-centers leads to the formation of a special energy spectrum of the electronic subsystem in metal oxides, which allows pair transitions of electrons. Paired electrons carry an electric charge without losing energy. Irradiation of multicomponent metal oxides with optical photons intensifies the process of formation of the maximum possible total length of U-centers clusters, therefore intensifies the process of metal oxides transition to a superconducting state: the temperature of the complete transition of these compounds to the superconducting state Tc can approach the value of the temperature of the opening of a pseudogap in the energy spectrum of electrons that is, this transition is realized at higher temperatures than it occurs under normal conditions.
Development of high quality teaching remotely is currently at the forefront of higher education developments. Particularly challenging is remote delivery of the teaching programs that require deep understanding of complex scientific phenomena, as well as development of practical skills and professional competencies. In this work, we discuss the experience of remote delivery of Physics degree. It is noted that different approaches are needed for different teaching elements. Based on this, we make recommendations for approaches to enhance student experience and to enable successful completion of the degree programs. Remote defense of the diploma projects in the format of research conference (using Zoom, Skype, GoogleMeet and other video communication) showed that this stage of the educational process is successfully implemented and is almost identical to the face-to-face defense. Consultations (on training courses, research projects, diploma projects) can be conducted remotely. When conducting written assessments of learning: tests, quizzes and examinations in the distance mode (using standard procedures such as distribution of questions and tasks), it is quite difficult to control the quality of students' performance, since there are opportunities for use various sources of information. A test system can provide a suitable substitute. The experience of conducting lectures and practical classes in the distance mode has shown that the lecturer does not have the feedback that occurs in classroom teaching. The lecturer is unable to interact with the audience, since students hardly ask questions and during the lecture they can go about their own business rather than listen to the lecturer.
The effect of high hydrostatic pressure 0 ≤ Р ≤ 17 kbar on the electrical resistance ρ(Т) in the basic ab-plane of praseodymium-doped single crystals of the Y1–xPrxBa2Cu3O7–δ system at 0 ≤ х ≤ 0.34 was investigated in the paper. Single crystals of compounds Y1–xPrxBa2Cu3O7–δ were grown by solution-melt technology in a gold crucible. Hydrostatic pressure was created in a piston-cylinder multiplier. The pressure was determined with a manganin manometer, and the temperature – with a copper-constantane thermocouple. It was established that an increase in pressure leads to an increase in the critical temperature of the studied compounds and a decrease in their electrical resistance, which corresponds to literature data for polycrystalline samples. Near the superconducting transition, the appearance of the temperature derivatives of the electrical resistance, dr/dT, of the Y1–xPrxBa2Cu3O7–δ compounds indicates a certain heterogeneity of the samples, i.e., the presence of areas in the samples with different temperatures of the superconducting transition, Tс, which transition to the superconducting state as Tс is reached. At intermediate concentrations of praseodymium, such regions pass into the superconducting state sequentially, but at x = 0 and x = 0.34, the form dr/dT indicates the presence of percolation paths for the flow of the transport current. The value of Tc and literature data on the Debye temperature indicate that the McMillan formula can be applied only to compounds Y1–xPrxBa2Cu3O7–δ that have Tc < 65 K (that is, for x, d > 0.3), and at the same time gives a very high values of the electron-phonon interaction constant, l ~ 1. It was found that, in contrast to pure YBa2Cu3O7–δ samples with optimal oxygen content, the application of high pressure leads to a multiple increase in the value of the baric derivative dTc/dP. It was established that within the limits of experimentally achieved pressures, there was no change in the sign of baric derivatives dTc/dP with increasing pressure, which was observed on polycrystalline samples with close values of praseodymium concentration. The possible mechanisms of the effect of high pressure on the critical temperature of the transition to the superconducting state Tc are discussed, taking into account the features in the electronic spectrum of carriers.
The paper investigates the effect of annealing at room temperature on the electrical resistance in the ab-plane ρab(T) of ReBa₂Cu₃O₇-δ (Re = Y, Ho) single crystals with oxygen deficiency. It was found that the reduction of oxygen content induces phase segregation, accompanied by the diffusion of a labile component and structural relaxation in the sample volume, confirming the critical role of oxygen deficiency in determining the structural and electrophysical properties of these materials. Annealing at room temperature with varying oxygen deficiencies results in an expansion of the linear range of ρab(T) and a narrowing of the temperature region where the pseudogap regime occurs, highlighting the importance of oxygen concentration in forming the electronic structure. Excess conductivity follows an exponential temperature dependence over a broad temperature range, indicating the presence of nonlinear effects. The pseudogap temperature dependence is well described within the BKD-BEK crossover theory, confirming a transition between two modes of material behavior. Replacing yttrium with holmium (Re = Ho) affects the charge distribution in the CuO planes, leading to disorder in the oxygen subsystem, which alters the electronic structure, manifesting as shifts in temperature regions corresponding to metal-insulator transitions and pseudogap anomaly. Thus, the results demonstrate that controlling the oxygen content and chemical composition of ReBa₂Cu₃O₇-δ crystals is an effective method for managing their electrophysical properties. The obtained short-range interatomic potential values can also be used for systematic studies of the complex behavior and defect chemistry of these materials at the atomic level. The use of "atomic scale techniques" allows not only for improving the physicochemical parameters of various rare earth oxides (REO) compounds but also for validating the adequacy of numerous current theoretical studies.
In bounds of the non-linear and system paradigms, been formulated by L. F. Chernogor in the last 1980th, all processes in open, non-linear, dynamical systems are very complex, non-linear, ultra-wideband or fractal ones. According to the fractal paradigm put forward in the early 2000s by V. V. Yanovsky, fractality is one of the fundamental properties of the surrounding world. Therefore, the study of fractal characteristics, in particular, of natural physical processes is actual, interesting and useful. The fractal dimension based on the Hurst exponent is one of the oldest and most famous ones. Based on the study of model fractal signals, it is demonstrated that the dependence between the estimate of the Hurst fractal dimension, obtained by the normalized range method, and its true value is significantly non-linear. To decrease of influence of the errors arising as a result of this, it is proposed to use the method of the corrective function. The practical effectiveness of the proposed method is demonstrated on the example of the analysis of experimental results obtained in the middle 1960s by H. E. Hurst, which discovered the presence of a somewhat strange grouping of the values of the Hurst fractal dimension around the value of 1.27 for various natural physical processes. A hypothesis about the possibility of explaining this fact precisely by the nonlinearity of the mentioned dependence for R/S-method was proposed.
The paper investigates the effect of high hydrostatic pressure on the conductivity, s(T), in the basic ab-plane of the HTSC single crystal Y0.66Pr0.34Ba2Cu3O7–δ. The YBa2Cu3O7–δ single crystal was grown using the well-known solution-melt technology. Y2O3, BaCO3, CuО and Pr5O11 compounds were used in the appropriate percentage ratio as initial components for growing Y0.66Pr0.34Ba2Cu3O7–δ single crystal. The modes of growth and oxygen saturation of the Y1–xPrxBa2Cu3O7–δ crystal were the same as for undoped single crystals. Electrical resistance in the ab-plane was measured according to the standard 4-pin method. Hydrostatic pressure was created in a piston-cylinder multiplier. The temperature dependences of the specific electrical resistance, r(Т), of the studied single crystals in the ab-plane in the temperature range Tc–300 K at pressures of 0–10 kbar were obtained experimentally. At all applied pressures, the experimental curves r(T) contain linear sections at temperatures T > T*. When T < T*, the r(T) curves deviate downward from their linear extrapolation, i.e., excess conductivity, Ds(T), appears in the studied samples. It was established that Ds(T) of the samples in a wide temperature range Tf < T < T* are characterized by an exponential temperature dependence Δs ~ (1–Т/Т*)exp(Δ*ab/T), where T* is the mean-field temperature of the superconducting transition, and can be interpreted in terms of the BCS-BEC crossover theory. Using this ratio, the temperature dependence of the pseudogap, Δ*ab(T), from T* to the temperatures corresponding to the maximum value of the pseudogap was constructed. An increase in the applied pressure leads to the effect of narrowing the temperature interval of realization of the pseudogap (PG) mode and, as a result, to the expansion of the interval of the linear dependence of the specific electrical resistance in the ab-plane. As the pressure increases, the temperature dependence of the pseudogap shows a crossover from the dependence of the BCS type to the dependence of the BEK type.
The article is devoted to the 110th anniversary of the birth of Valerian Ivanovych Startsev, Doctor of Physical and Mathematical Sciences, Professor, Honored Worker of Science and Technology of the Ukrainian SSR, an outstanding scientist in the field of crystal physics, physics of strength and plasticity, a well-known organizer of science and education in Kharkiv. Information about his scientific, scientific-organizational, scientific-pedagogical activities is presented. A brief overview of the fundamental and applied research conducted under the leadership and with the direct participation of V. I. Startsev is given. The results of these studies were included in the fund of ideas of modern science about the strength and plasticity of solids, stimulated the development of the physical theory of plasticity and dislocation physics.
The article examines the effect of plasmon resonance of gold nanoparticles on the luminescent properties of molecular aggregates (J-aggregates) of two cyanine dyes, PIC and TDBC. It is shown that the luminescence enhancement of J-aggregates due to the exciton-plasmon interaction occurs in a very similar manner for both types of aggregates, namely: the largest enhancement factor is achieved at a distance between J-aggregates and nanoparticles of 15-20 nm, while the exciton delocalization length increases and increasing their lifetime, as well as suppressing the process of exciton self-trapping. However, these effects are more pronounced for PIC J-aggregates than for TDBC J-aggregates, despite the latter exhibiting better excitonic characteristics. It is proposed that the main factor of the detected discrepancies is the different structure of the exciton bands for J-aggregates and, accordingly, the different degree of overlap of their absorption bands with the plasmon resonance band of gold nanoparticles.
The article presents the results of research aimed at summarizing experimental data on the mechanical behavior, structural state and mechanisms of superplastic deformation of aluminum alloys Al-4 wt.% Ge, Al-4.1 wt.% Cu-0,5 wt.% Zr, 1420T, 1933. It is revealed that the initial microstructure of Al-4 wt.% Ge alloy samples is coarse-grained. Initial microstructure of 1420Т and 1933 alloy samples is bimodal. The study of characteristic types of samples microstructure deformed under the optimal conditions showed that the average grain size d av in samples of Al-4.1 wt.% Cu-0.5 wt.% Zr and 1420T alloys increases slightly. It is revealed that in the course of superplastic deformation of Al-4 wt.% Ge and 1933 alloy samples, recrystallization takes place intensively, it leads to an increase in the initial grain sizes. Accumulation of cavities in the samples of all studied alloys during superplastic flow is observed. In the samples of alloys 1420T and 1933 during superplastic deformation, structural changes occur, which are probably associated with local melting of the alloys. The viscous flow of the metastable liquid-solid phase localized at the grain boundaries leads to the formation of fibrous structures in cavities and cracks. The study of the deformation relief of the samples gives grounds for asserting that their superplastic deformation takes place due to the cooperative development of deformation and accommodation mechanisms, namely grain boundary sliding, intragranular dislocation sliding and diffusion creep. The contribution of grain boundary sliding to the overall deformation of the samples was analyzed, as well as the likely influence of liquid phase inclusions on the mechanism of superplastic deformation of samples that exhibit the effect of structural superplasticity in the solid-liquid state.
Carbonated hydroxyapatite (CHA) is the basic mineral component of animal and human bone. Therefore, it is widely used in medicine to repair bone defects. In orthopedic surgeries, ceramic implants are usually used as a biologically active defect filler. In the lattice of CHA carbonate ions can occupy two non-equivalent positions - A and B. A position corresponds to the position of OH- anions in the lattice of hydroxyapatite (HA), and B - PO43-. It is well known that substitution of B-positions with carbonate groups leads to significant distortions of HA lattice, which causes microstresses and crystalline defects in it. Therefore, CHA ceramics as a result of sintering is characterized by significant internal stresses whose relaxation at room temperature can lead to a change in both its phase composition and biological activity. By methods of chemical and X-ray structural analysis, infrared spectroscopy and electron scanning microscopy the ageing process of pressed CHA at room temperature, sintered in an atmosphere of dry carbon dioxide at temperatures 800÷1200 °C was studied. The phase composition and structure of freshly prepared and aged for two years ceramic samples were compared. It is shown that relaxation of internal stresses arising during sintering of presses causes plastic deformation of crystallites accompanied by redistribution of carbonate ions from B to A-position. As a result, displacement of OH- ions from channel (A) positions and decomposition of B-type CHA on CaO and A-type CHA becomes energetically advantageous.
The laureates of the 2023 Nobel Prize in Physics are three researchers: Pierre Agostini (The Ohio State University, USA), Ferenc Krausz (Max Planck Institute of Quantum Optics, Garching and Ludwig-Maximilians-Universität München, Germany), and Anne L'Huillier (Lund University, Sweden). The prize was awarded for developing experimental methods that allow the generation of extremely short (attosecond) laser light pulses to study the dynamics of electrons in matter. The paper presents information about the scientific achievements of this year's Nobel laureates, which "give humanity new tools for exploring the world of electrons inside atoms and molecules." The paper describes the fundamental physical experiments that launched the new scientific field of attosecond physics. With its development, world science has gained many opportunities to study various fundamental physical processes and phenomena, as well as to create cutting-edge technologies, a brief overview of which is provided in the paper. A description of the new physical phenomenon discovered by the laureates, which was called electron-ion recollision, is given.
The problem of the influence of a defect ensemble and long-term exposure in an air atmosphere on various mechanisms of electrical transport of HTSC compounds Re1Ba2Cu3O7-δ (Re = Y or other rare earth ion) is considered. The features of the crystal structure and the influence of structural defects of various morphologies on the electrical conductivity of these compounds in the normal, pseudogap, and superconducting states are discussed. A review of experimental data obtained from studies of the effect of long-term aging in air on various mechanisms of electrical transport of Re1Ba2Cu3O7-δ compounds of various compositions and technological backgrounds is carried out. The effect of long aging on stability of the oxygen subsystem and the electrical resistance of pure and aluminum-doped YBa2Cu3O7-δ single crystals with a given topology of planar defects have been studied. Various theoretical models are discussed on the effect of long-term exposure in an air atmosphere on the electrical conductivity of HTSC compounds of the 1-2-3 system.
The functional characteristics of hydroxyapatite, which has carbonate impurities inside the hydroxyapatite crystal lattice after sintering in the temperature interval from room temperature to 1400°C have been studied. It has been shown, that carbonate impurities are present in hydroxyapatite up to 1000°C. Hydroxyapatite has a mixed AB - type of carbonate substitution. It has been shown, that all samples after the heating and sintering in the temperature interval from room to 1400°C contain single phase hydroxyapatite. The samples have density greater than 95% of the theoretical for hydroxyapatite at the temperature of 1200°C. The active shrinkage of the samples starts at temperature near 700°C and reaches the maximum value at 1280°C. The same tendency was demonstrated by the dependence of Vickers microhardness on sintered temperature. The maximum Vickers microhardness of 5.5 GPa was obtained in this work on the samples of hydroxyapatite after sintering at the temperature of 1100°C. The mechanisms of the hydroxyapatite sintering at 1150°C have been studied. It has been shown, that the diffusion during the sintering of the samples is realized by the surface diffusion mechanism, as well as through the interface grain boundaries in the polycrystalline hydroxyapatite. The microstructure of the hydroxyapatite particles after heating at high temperatures was studied. It has been shown, that at the initial stage of the sintering of hydroxyapatite, active mass transfer take place, which at the temperature of 1000°C leads to the sintering of the particles with neck formations between them. The Arenerus plot of the size of hydroxyapatite particles as a function of the heating temperature was obtained. The activation energy for diffusion processes in the particles at different temperatures was calculated. The obtained values were 36, 83, 5.11 and 11.28 kcal/mol at different intervals for the heating of hydroxyapatite.
Today, solid solutions based on antimony and bismuth tellurides are among the most widely used materials for the p-legs of thermoelectric converters used at room temperature and below. This paper presents the results of a study of galvanomagnetic properties (electrical conductivity σ, Hall coefficient RH, Hall mobility of charge carriers μH) of thermoelectric solid solutions (Bi1-хSbх)2Te3 in the range of compositions close to pure antimony telluride (x = 1 – 0.96) at temperatures T = 80 K and T = 300 K. The study was carried out on cast polycrystalline samples obtained by the method of crystallization from the melt followed by long-term annealing in vacuum at a temperature of T = 650 K. Galvanomagnetic properties were measured by the standard dc-method, the experimental cell was cooled with liquid nitrogen. The measurement error of RH and σ did not exceed ± 5%. It is shown that the introduction of the first portions of Bi2Te3 leads to a sharp decrease in σ, which is associated with a high degree of disorder of the crystal lattice. In the range of compositions x = 0.99 – 0.9825, the concentration dependences of σ(x) and μH(x) revealed anomalous growth of σ and μH. The presence of concentration anomalies is associated with the transition from dilute to concentrated solid solutions. An assumption is made about the percolation nature of the phase transition. Within the framework of the problem of spheres of percolation theory, within the framework of the task of spheres of the theory of percolation the radius of the deformation sphere of an impurity atom (Bi) is estimated. The obtained value is consistent with the short-range potential of the impurity. It is shown that the position of the anomalies in the σ(x) and μH(x) dependences does not change with the decrease in temperature down to 80K. Thus, the observation of concentration anomalies of the properties for the solid solution (Bi1-xSbx)2Te3 is another confirmation of the hypothesis about the universal nature of the behavior of solid solutions at a low impurity concentration. The detected anomalies must be taken into account when developing methods for increasing the thermoelectric performance of materials by creating solid solutions and doping.
An effective way to create self-organizing arrays of metal particles is to melt thin layers of substance on a poorly wetted surface. Such arrays may improve the technological properties of functional structures, and are themselves functional elements of modern devices and systems. During the melting of a solid layer on a poorly wetted substrate, an array of spherical particles is formed, which are evenly distributed over the surface of the substrate. The distribution of particles by size is determined by the thickness of the fusible layer and conditions of the deposition. The location of islands, formed after the melting of vapour-crystal deposited solid films, is determined primarily by the initial stages of de-wetting, when the thin continuous film starts to decay while remaining in solid state. This work studied self-organizing processes during the melting of Pb films deposited on a Ta substrate. The films were deposited on glass plates in a high vacuum and then after deposition were heated to a temperature slightly above the Pb melting point. After the heat treatment the samples were removed from the vacuum chamber and examined using SEM microscopy and EDS analysis. It was discovered that arrays of spherical particles are formed during the melting of micron-thick Pb films. The histograms of the size distribution of such particles are quite wide and can be represented as bimodal with partially overlapping maxima. This can be explained by active coalescence processes in thicker samples. This study demonstrated that small temperature gradients can cause noticeable kinetic effects that allow separate particles to move macroscopic distances and capture the surrounding substance. The study also estimated the energy associated with the optimization of the morphological structure of vacuum condensate and which is a physical factor of de-wetting.
The work presents the result of modernization of the equipment and methods of performing the work of the general physics laboratory practice. Modernization was carried out with the aim of giving the work of the workshop elements of research activity. Using the example of thematically related laboratory works from the section "Electricity and Magnetism", it is shown that the combination of several laboratory works into one study of the electrophysical properties of semiconductor materials provides an opportunity to gain deeper knowledge about the object of research and contributes to the development of research activity skills of physics students. The work investigated semiconductor diodes manufactured using different technologies: Schottky diode MBR2045, high-voltage p – i – n diode STTH6012 and diode with p – n junction D92 – 02. The study consisted of studying volt-ampere, volt-farad characteristics and temperature dependences of the reverse current of each of the specified products. The measurement results were processed using modern theoretical models of semiconductors. The equipment and skills acquired by students during the performance of such complex laboratory work can be used in research work if there are appropriate tasks.
The influence of medium doses (from 1019 cm–2 to 1020 cm–2) of irradiation with fast electrons and changes in the concentration of praseodymium in the interval 0.0 ≤ z ≤ 0.5 on the excess conductivity of optimally oxygen-doped Y1Ba2Cu3O7-δ single crystals was studied. It is shown that electron irradiation and an increase in the degree of doping with praseodymium leads to a significant expansion of the temperature interval of the existence of excess conductivity, thereby narrowing the region of the linear dependence of r(Т) in the ab-plane. It was established that at doses 0 ≤ D ≤ 6.5´1019 cm–2 the value of the value of the transverse coherence length ξс(0) increases with an increase in D approximately 3 times and more than four times as the praseodymium content in the sample increases to z ≈ 0.42. At the same time, in both cases, the 2D-3D crossover point is shifted by temperature. In contrast to the case of irradiation with small doses (D ≤ 1019 cm–2) and doping with praseodymium up to concentrations z ≤ 0.39, irradiation with medium doses and doping with praseodymium at higher concentrations leads to a non-monotonic dependence of the transverse coherence length xс(0) with characteristic maxima at D ~ (7-8)´1019 cm–2 and z ≈ 0.42, which may be related to the general suppression of superconducting characteristics.
The paper discusses the conditions under which superconductivity of metals would be detected at atmospheric pressure and at room temperature. One of the possible directions of research to achieve these conditions is to change the phonon spectrum of metals in order to increase the Debye temperature, and therefore to increase the temperature of the superconducting transition Tc. According to the idea of the work and to the estimates made in it, the maximum frequency of phonons nmax in metals can be increased by the short-term action of an external constant electric field (electric pulse). The duration of the pulse should be (10–5–10–7) s. The voltage of the constant electric field source is U » 1V. A decrease in the crystal lattice parameter should be accompanied by an increase in the maximum phonon frequency nmax and, accordingly, by an increase in the Debye temperature. The characteristic size of the sample, in which the change in electron concentration can be realized, should not exceed the length of electron shielding in metals, i. e. ≈ 10–8 m. The sequential action of a certain number of electric field pulses can maintain a superconducting state in a metal sample for some finite time.
The paper considers the possibility of using the method of heterovalent doping to improve the functional characteristics (light output and afterglow level) of composite scintillators based on ZnWO4 micropowder obtained by solid-stase synthesis. LiNO3, Li2SO4, Cs2SO4, Rb2SO4 were added to the mixture of initial ZnO and WO3 oxides in the amount of 0.003 wt. %. The synthesis was carried out in air at a temperature of 950 °C for 30 hours. The study of the morphology of the obtained powders was carried out by scanning electron microscopy (SEM). It has been shown that the grain size of the synthesized powders dependence on a greater extent by the radius of the cation replacing Zn2+ than by the presence of a mineralizer with a low melting point. The studied anions do not affect the synthesis process, and when ZnSO4 is added, the size of the obtained grains is similar to the nominally pure synthesized ZnWO4 (2-5 μm). When ZnWO4 is doped with 20% less Li+ relative to Zn2+, regardless of the form of introduction (anionic component), the average grain size increases by 4 times. When ZnWO4 doped with Rb+ and Cs+, which are twice as large as Zn2+, grains increase by a factor of 20. It happened because of a significant loosening of the crystal lattice formed by zero-dimensional defects, which contributes to better diffusion of reagents and acceleration of the synthesis process. The study of X-ray luminescence showed that the spectra of the synthesized powders coincide in terms of the peak position with the spectrum of the ZnWO4 single crystal, which corresponds to the emission on the WO6 6- oxyanion complex. The intensity of the bands increases with increasing dopant’s cationic radius: Li+ → Rb+ → Cs+. The maximum X-ray luminescence intensity is observed for the ZnWO4:Cs+ micropowder, which is two times higher than the intensity of the undoped ZnWO4 micropowder. This is due to a rather high degree of deformation of the structure of the WO6 emission center, which, in turn, affects the luminescent properties of the material. Composite samples based on the synthesized micropowders were prepared using SKTN optically transparent rubber as a binder in an amount of 50 wt.%. The results of measurements of the relative light output of composite scintillators based on ZnWO4:Me+ correlate with the results of measurements of the X-ray luminescence intensity of the synthesized powders. An increase in the value of the light output with an increase in the radius of the dopant cation is observed. Measurement of the afterglow level showed that the use of the heterovalent doping method, namely Me+ in our work, is an effective way to improve the scintillation parameters of crystalline materials. Composite scintillators based on ZnWO4:Cs+ and ZnWO4:Rb+ demonstrate the values of light output and afterglow at the level of a composite from a crushed ZnWO4 single crystal, and no worse than a single crystal ZnWO4 sample. The obtained materials are promising for use as scintillation detectors in computed tomography and digital radiography devices.
Calcium phosphate materials have been widely used in medical practice for decades. Due to their bioactivity and integration with human hard tissues. They have been produced in the form of dense and porous ceramics, powders and needle-like crystals (whiskers). Despite the high mechanical properties (hardness, compressive strength), calcium phosphate ceramics are mainly used in medicine mainly as the fillers for bone defects formed due to injuries or diseases because they have high fragility and low crack resistance. These circumstances do not allow using them in the sites that have high mechanical loads (e.g. hip surgery). To solve these problems metal implants are used. Among them, Ti-based alloys are the most widely used due to its high mechanical properties, biocompatibility and high corrosion resistance. Recently, the data on the use of MAX phases as medical materials to create the composites based on Ti3SiC2 have appeared in the literature. Calcium phosphate coatings were obtained on Ti3AlC2 substrate by the sol-gel method. The effect of temperature, holding time, chemical compositions of reactants on the phase composition and structure of the samples are discussed. XRD measurements have revealed that the initial coatings consists of nanoparticles sized 10-50 nm. Light and scanning electron microscopy (SEM) were applied to study the morphology of the coatings. It have been shown that the coatings had thickness in an interval 40-100 mm and had the homogenous structure. It has been established by X-ray phase identification that the coating after heating at 1000oC during 1 hour contained b-tricalcium phosphate (b-TCP). It was found, that the thickness and phase composition of coatings depend on the time of coating in calcium phosphate solution. The optimal conditions for the formation of coatings are established.
