Abstract The effect of the terrestrial gravitation field on crystal growth from a solution–melt during spontaneous crystallization is considered, taking into account that the space station (SS) and a laboratory at the Earth, in which the crystallization processes occur, are a noninertial system. It is shown that the specific feature that distinguishes the crystal growth in the terrestrial conditions is the pressure in the melt caused by the supporting force (the Newton third law). This pressure is absent at SS, and this fact leads to an increase in the unit cell of the melt that undergoes the first-order phase transition. As a result, the crystals grown at the SS have larger sizes than the same crystals grown in terrestrial conditions. They also exhibit an excess stress, the value of which is equal to the support pressure, which is absent at the SS. This situation is compared to the experimental data on growing CrSi_2 crystals from a solution–melt in Zn of the Cr–Si–Zn system.

The effect of the terrestrial gravitation field on crystal growth from a solution–melt during spontaneous crystallization is considered, taking into account that the space station (SS) and a laboratory at the Earth, in which the crystallization processes occur, are a noninertial system. It is shown that the specific feature that distinguishes the crystal growth in the terrestrial conditions is the pressure in the melt caused by the supporting force (the Newton third law). This pressure is absent at SS, and this fact leads to an increase in the unit cell of the melt that undergoes the first-order phase transition. As a result, the crystals grown at the SS have larger sizes than the same crystals grown in terrestrial conditions. They also exhibit an excess stress, the value of which is equal to the support pressure, which is absent at the SS. This situation is compared to the experimental data on growing CrSi 2 crystals from a solution–melt in Zn of the Cr–Si–Zn system.

We have analyzed crystal growth in “terrestrial” conditions and in conditions on a space station. It is shown that CrSi2 crystals grown from the Zn melt of the Cr–Si–Zn system in zero-gravity conditions exhibit an excess stress comparable with the excess pressure in the melt due to the support reaction on Earth, as well as the Laplace pressure.

It is shown that CrSi2 crystals are grown from the Zn melt of Cr-Si-Zn system in «weightlessness” conditions have excessive stress. This stress is comparable in magnitude to the excess pressure in the melt. This overpressure is caused by the reaction of the "support" on Earth to this melt, plus (with the corresponding sign) the Laplace pressure

It is reported that two compounds containing several rare earth elements (RE) simultaneously was obtained recently. It is proposed to call them polyelement solid solutions - (PSS). Single crystals of RE hexaborides and RE digallides PSS were obtained, some of their characteristics and features are given. These PSS were obtained by mass crystallization from melts - solutions in Al (hexaborides) and Ga (digallides). PSS hexaborides exhibit a "densification" of their crystal structure when RE atoms are introduced into the base LaB6 crystal lattice. The incorporation is facilitated by the presence of a homogeneity region in RE hexaborides and RE digallides. The stepwise chemical analysis of the recently obtained 6-element PSS of lanthanum hexaborides and digallides shows a high uniformity of the RE distribution along the sample. The complex process of the formation of PSS of hexaborides RE and digallides of RE is analyzed and the possibility of obtaining different groups of PSS is discussed.

A design for a high-efficiency single-photon detector based on lanthanum and cerium hexaborides, which operates from the infrared to ultraviolet spectral ranges, is suggested. The results of computer simulations of heat transfer in the sensitive element of the detector upon the absorption of photons with energies of 0.5–4.13 eV are presented. To attain a high efficiency of the system of photon detection in the wavelength range from near infrared to ultraviolet, lanthanum hexaboride is proposed as the absorber and heat-sink material in the sensitive element. It is shown that a sensitive element of both single- and three-layer design made entirely of hexaborides will possess a gigahertz counting rate and a detection efficiency exceeding 90%.

AbstractA design for a high-efficiency single-photon detector based on lanthanum and cerium hexaborides, which operates from the infrared to ultraviolet spectral ranges, is suggested. The results of computer simulations of heat transfer in the sensitive element of the detector upon the absorption of photons with energies of 0.5–4.13 eV are presented. To attain a high efficiency of the system of photon detection in the wavelength range from near infrared to ultraviolet, lanthanum hexaboride is proposed as the absorber and heat-sink material in the sensitive element. It is shown that a sensitive element of both single- and three-layer design made entirely of hexaborides will possess a gigahertz counting rate and a detection efficiency exceeding 90%.

Experimental data obtained in a study of CrSi 2 microcrystals grown under microgravity conditions from a Zn melt in the Cr–Si–Zn system by the mass crystallization method and then placed in terrestrial conditions are presented and analyzed. New properties of crystals of this kind are observed.

Experimental data and their analysis on the study of Cr〖Si〗_2 microcrystals grown in weightlessness from the melt Zn of Cr-Si-Zn system by mass crystallization and placed in earth conditions are presented. New properties of such crystals are found.

K. Chen,1,* T-C. Weng,2 G. Schmerber,3 V. N. Gurin,4 J.-P. Kappler,1 Q. Kong,1 F. Baudelet,1 A. Polian,1,5 and L. Nataf1 1Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin-BP48, 91192 Gif-sur-Yvette Cedex, France 2Center for High Pressure Science & Technology Advanced Research, 1690 Cailun Road, 201203 Shanghai, China 3IPCMS, CNRS-Université de Strasbourg, 23 rue du Loess, BP 43, 67034 Strasbourg Cedex 2, France 4Ioffe Institute, Russian Academy of Sciences, St. Petersburg 194021, Russia 5IMPMC, Sorbonne Université, C.N.R.S. UMR 7590, 4 Place Jussieu, 75005 Paris, France

AbstractThe formation of the protective and hardening oxide coatings on the surface of the single-crystal sapphire and sintered corundum (ceramics) is studied. Corundum systems with oxide coatings are as yet unknown and our studies are original. The compositions of the coating based on the mixture of Al_2O_3 and B_2O_3 oxides and a technique of their deposition on the samples are worked out. The strength of the samples during the bending test is studied. It is shown that the hardening of several samples achieves ~30% and microhardness (HV) reaches 30 GPa. Basing on the results of an investigation of the significant number of the samples obtained under different conditions, it is concluded that the developed method of the protection and hardening of the corundum products is promising.

Motivated by the prediction of surface Kondo breakdown in topological Kondo insulators, we investigated the valence and magnetism of SmB6 with x-ray absorption and magnetic circular dichroism at the Sm M-4,M-5 and L-2 edges with surface and bulk sensitivity, respectively. A higher Sm valence state at the surface and in the bulk under pressure indicates the surface- and pressure-induced bulk Kondo breakdown. We confirmed the different magnetization origin from the surface (f electron) to the bulk (d electron) and ascertained the direct relationship between the disappearance of the Sm L2-edge x-ray magnetic circular dichroism signal and the closure of the d-f hybridization gap in SmB6 bulk under pressure, paving the way for further investigations of the Kondo insulators. Above P-c = 8.5 GPa, a more localized 4f state with higher valence and the disappearing of the 5d magnetism are observed, suggesting the closure of the hybridization gap in the bulk.

Monocrystals of lanthanum hexaboride LaB6 containing both natural boron and its isotopes 10B and 11B have been produced using the solution-melt method. Polyelement hexaboride rare-earths have been grown and the corresponding ceramics have been synthesized for the first time. All these crystals have been studied by means of various techniques, generally using Raman scattering. The Raman spectra attributed to various spectral lines corresponding to nonanalyzable representations have been obtained and interpreted. Frequencies and half-widths of spectral lines have been obtained, the removal of degeneracy and the development of respective splitting of degenerate oscillations induced by defects, mainly by boron isotope inclusions, have been identified. The influence of defects on the Raman spectra has been determined.

The formation of the protective and hardening oxide coatings on the surface of the single-crystal sapphire and sintered corundum (ceramics) is studied. Corundum systems with oxide coatings are as yet unknown and our studies are original. The compositions of the coating based on the mixture of Al2O3 and B2O3 oxides and a technique of their deposition on the samples are worked out. The strength of the samples during the bending test is studied. It is shown that the hardening of several samples achieves ~30% and microhardness (HV) reaches 30 GPa. Basing on the results of an investigation of the significant number of the samples obtained under different conditions, it is concluded that the developed method of the protection and hardening of the corundum products is promising.

AbstractMonocrystals of lanthanum hexaboride LaB_6 containing both natural boron and its isotopes ^10B and ^11B have been produced using the solution-melt method. Polyelement hexaboride rare-earths have been grown and the corresponding ceramics have been synthesized for the first time. All these crystals have been studied by means of various techniques, generally using Raman scattering. The Raman spectra attributed to various spectral lines corresponding to nonanalyzable representations have been obtained and interpreted. Frequencies and half-widths of spectral lines have been obtained, the removal of degeneracy and the development of respective splitting of degenerate oscillations induced by defects, mainly by boron isotope inclusions, have been identified. The influence of defects on the Raman spectra has been determined.

Методом электронно-лучевого напыления получены пленки гексаборида церия --- материала, перспективного для использования в термоэлектрических устройствах при гелиевых температурах. Напыление проводили с керамических мишеней на диэлектрические, полупроводниковые и металлические подложки при различных температурах. Подробно исследованы микроструктура, элементный и фазовый составы, температурные зависимости удельного сопротивления и коэффициента Зеебека. Получены пленки со структурой CaB6, характерной для гексаборида церия, и элементным составом, близким к стехиометрическому. При низких температурах пленки имеют удельное сопротивление несколько больше, а коэффициент Зеебека близок к значениям для монокристаллических образцов. Основной причиной различия величин удельного сопротивления является обнаруженная в пленках большая концентрация примеси кислорода. DOI: 10.21883/FTP.2017.08.44783.52

The results of the numerical simulation of heat propagation processes occurring after the absorption of single photons with energies of 1 eV–1 keV in a three-layer sensor of a thermoelectric detector are analyzed. Different configurations of the sensor with a tungsten absorber, a thermoelectric layer of cerium hexaboride, and a tungsten heat sink are considered. It is shown that sensors for detecting photons of a specific spectral range with the required energy resolution and counting rate can be developed by varying the geometric sizes of the sensor layers. It is concluded that a three-layer sensor has a number of advantages in comparison with a single-layer sensor and has characteristics allowing consideration of the thermoelectric detector as a realistic alternative to superconducting single-photon detectors.

Films of cerium hexaboride, a material promising for use in thermoelectric devices at liquidhelium temperatures, are produced by electron-beam deposition. Deposition is carried out from ceramic targets onto insulator, semiconductor, and metal substrates at different temperatures. The microstructure, the elemental and phase compositions, the temperature dependences of the resistivity and the Seebeck coefficient are thoroughly studied. CaB6-structured films, for which the structure is characteristic of cerium hexaboride and the elemental composition is close to the stoichiometric composition, are obtained. At low temperatures, the resistivity of the films is somewhat higher than that of single-crystal samples, and the Seebeck coefficient is close to the corresponding coefficient for single-crystal samples. The main cause of the difference between the resistance values is a high concentration of oxygen impurity detected in the films.

Анализируются результаты компьютерного моделирования процессов распространения тепла, протекающих после поглощения одиночных фотонов с энергией 1 эВ-1 кэВ в трехслойном сенсоре термоэлектрического детектора. Рассмотрены различные геометрии сенсора с вольфрамовым поглотителем, термоэлектрическим слоем из гексаборида церия и вольфрамовым теплоотводом. Показано, что посредством изменения геометрических размеров слоев сенсора можно получать датчики для регистрации фотонов конкретного спектрального диапазона с необходимыми энергетическим разрешением и скоростью счета. Сделан вывод, что трехслойный сенсор имеет ряд преимуществ по сравнению с однослойным сенсором и обладает характеристиками, позволяющими рассматривать термоэлектрический детектор как реальную альтернативу сверхпроводящим однофотонным детекторам. DOI: 10.21883/FTP.2017.07.44639.25

A new design of the sensor for thermoelectric single-photon detector is proposed. The results of modelling of kinetic processes in the sensor of thermoelectric single-photon detector after absorption IR-X-ray photons in different parts of the absorber for different geometries of the W/(La, Ce)B-6/W/Al2O3 multi-layer sensor are presented. It is shown, that thermoelectric detectors with multi-layer sensor have high energy resolution, gigahertz count rate and can be a real competitor to superconducting detectors.