Crystalline ceramic material (Gd,Y)3Al2Ga3O12 codoped with Ce and Tb (GYAGG: Ce, Tb) was demonstrated to be a high light yield scintillator. The luminescence kinetics was proven to be formed by the combining of the direct Tb3+→Ce3+ and inverse Ce3+→Tb3+ transfer of electronic excitations. This forms a mechanism leading to the increase of the slow component fraction in the scintillation and limits the application of the material, when a fast response is required. However, a high light yield opens an opportunity to utilize the developed material for application in the detectors operating in a current measurement mode and, in long living, as high-flux sources of optical photons under the ionizing radiation of a different type.

GYAGG:Tb (Ce) scintillators have been confirmed to be promising sources of light emission when excited by an intense 150 keV electron beam. The saturation of the scintillation yield under such excitation conditions has been studied. To explain the results obtained, a model that considers the Auger quenching mechanism was used. The Ce-doped material did not show saturation, whereas a moderate 30% drop of the yield was measured in the Tb-doped sample at the highest excitation beam intensity ~1 A/cm2. This put forward a way to exploit the Tb-doped scintillator for indirect β-voltaic batteries.

The luminescent Z-scan technique with time resolution is applied to the study of the luminescence properties of CH3NH3PbBr3 single crystals representative of the family of hybrid organic–inorganic lead perovskites successfully applied recently in photovoltaics and currently investigated as potential nanosecond scintillators. The third harmonic of Ti-sapphire laser (λ = 266 nm) with a pulse duration of 26 fs and 1 kHz frequency was applied for the luminescence excitation creating the charge carriers with the estimated density from 1017 to 1021 cm−3 in the temperature range from 13 to 300 K. Temperature and excitation density dependence of the luminescence yield and kinetics is interpreted with the consideration of the temperature-dependent binding of electrons and holes into excitons, a saturation of defects responsible for the non-radiative relaxation channel competing with exciton creation; absorption saturation resulting in the increased penetration depth of the excitation radiation and hence the increased contribution of the re-absorption.

A mechanism of firefly high‐scintillation light yield (LY) of Tb‐doped quaternary (Gd, Y)3Al2Ga3O12 garnet ceramics is reported. Through measurements with the synchrotron source, the high efficiency of the luminescence excitation, providing a quantum yield Q > 1 below the photon multiplication energy range, is defined. The excitation efficiency reaches two at the excitation energy slightly above 2Eg. The cascade of photons is explained by combining three factors: first, the high quantum yield Q ≈ 1 of the luminescence at excitation in lower mixed states 4f75d1 with high spin (HS) and low spin (LS); second, the cross‐relaxation 4f7(6P)5d1(HS) → 4f7(8S)5d1(HS) provides the excitation of 4f8(7F0) →4f8(5D1,4) transition of the 4f8 configuration of the same or neighboring Tb ion, which is followed by the luminescence from 5D1,4; and finally, the relaxation of 4f7(8S)5d1‐5(HS) configuration into the excited 4f8 configuration occurs with future emission from 4f8(5D1,4) states. This cascade forms the final stage of the scintillation in the compound being studied and provides a LY twice as high compared with the material when doped with Ce.

Two series of (Gd, Y, Yb)3Al2Ga3O12 quintuple compounds with a garnet structure and solely doped with Ce and Tb were prepared in the form of ceramics by sintering in oxygen at 1600 °C for two hours and studied for the interaction of activator ions with ytterbium ions entering the matrix. It was shown that the photoluminescence and scintillation of Ce3+ ions are completely suppressed, predominantly by tunneling ionization through the charge transfer state (CTS) of the Ce4+-Yb2+ ions. The photoluminescence of Tb3+ ions is quenched in the presence of ytterbium, but not completely due to the poor resonance conditions of Tb3+ intraconfiguration transitions and the CTS of the single Yb3+ and the CTS of Ce4+-Yb2+ ions. The scintillation in the visible range of both Ce3+- and Tb3+-doped samples is intensely quenched as well, which indicates strong competition from Yb3+ ions to activators in interaction with the Gd substrate.

Technological factors and processes contributing to the scintillation mechanism have been considered in quaternary garnet ceramics doped with Ce(Gd,Lu)3Al2Ga3O12. The super-stoichiometric additive of gadolinium in the material composition or its co-doping with a low concentration of Mg were found to be effective tools to suppress phosphorescence in the quaternary garnet, confirming that it is not an intrinsic property of the material. The Monte-Carlo simulation of electronic excitation transfer demonstrates that the hopping migration along the gadolinium sublattice plays an essential role in forming the scintillation kinetic parameters. Breaking the integrity of the gadolinium sublattice by substitution with heavier lutetium ions increases the role of self-trapped states in the excitation of Ce3+ ions, which ensures both an increase in the fraction of short ~20 ns and very long ~600 ns components in the scintillation kinetics.

Ceramics of quaternary garnets (Gd,Y)3Al2Ga3O12 doped with Ce, Tb have been fabricated and evaluated as prospective materials for indirect energy converters of α-and β-voltaic. Samples were characterized at excitation with an X-ray source and an intense 150 keV electron beam and showed good temperature stability of their emission and tolerance to irradiation. The role of X-rays accompanied the α-particle emitting in the increase of the conversion efficiency is clarified. The garnet-type structure of the matrix in the developed materials allows the production of quality crystalline mass with a light yield exceeding that of the commonly used YAG: Ce scintillator by a factor of two times.

The diamond composite materials with embedded yttrium-aluminum garnet doped with cerium (YAG:Ce) nanoparticles have been produced by microwave plasma-assisted chemical vapor deposition (CVD). Nanoparticles were synthesized by co-precipitation from an aqueous solution while CVD diamond served as the transparent matrix with high thermal conductivity, hardness, and resistivity to radiation damage. The composite films show high-intensity X-ray luminescence (XRL) with a broad band peaking around the wavelength of 550 nm (5d -> 4f transition in Ce3+ ion), and a narrow peak of silicon-vacancy (SieV) centers at 738 nm. The characteristic decay time was measured at tau(Ce) < 50 ns for cerium emission and at tau(SiV similar to 1) ns for SieV centers. Excitation spectra of both luminescence types measured near yttrium K-edge (17.1 keV) show a strong correlation, attributed to the excitation of SieV luminescence by photoelectrons ejected from YAG:Ce nanoparticles. The discovered phenomenon suggests a new way to control X-ray visualization by luminescent diamond composites for fast X-ray detectors and screens. (C) 2020 Elsevier Ltd. All rights reserved.

The work motivation is caused by the need to increase service life of aerospace components by developing the methods of thermal barrier coatings on structural materials The main aim of the paper is to study thermal barrier coating structures formed by plasma spraying of yttria-stabilized zirconia. The methods used in the study is the nuclear backscattering spectrometry. The results: Using the methods of nuclear backscattering spectrometry the authors have investigated the element composition, structure and thickness of plasma-sprayed yttria-stabilized zirconia coatings. The intermediate layer between coatings and base material was founded. The total porosity of the coatings, evaluated by comparison of massand geometric thicknesses, is 20...30 %. It was shown, that due to high speeds of low-pressure plasma spraying the mixed coatings can be formed in case of layer-by-layer deposition of nickel and yttria-stabilized zirconia powders. The total porosity tends to decrease with the increase number of layers. For the coating formed by plasma spraying through the mask with holes, the periodically changing coating thickness was determined.

This study presents the results of metric and trace-wear analyses, as well as elemental composition analysis using the mass-spectrometry with inductively coupled plasma (ICP-MS) of 42 sickles from the Sosnovaya Maza hoard from State Historical Museum. The main components of the alloy in all cases were identified as Cu (91.30–99.19%) and Fe (0.02–7.85%). The trace-wear analysis of sickles has revealed many traces on surfaces of the items that were assigned to three technological phases: casting, post-casting processing, and probable use of the sickles. The comparison of metric and trace-wear analyses results provide to identify eight subgroups of sickles. Each subgroup was supposedly cast in a single mold.

Thin-film diamond–rare earth fluoride nanocomposites have been produced by chemical vapor deposition to be used as a source of intensive photo- and X-ray luminescence. The composites with embedded Eu-containing nanoparticles show high-intensity orange narrow-band photoluminescence near the wavelength of 612 nm. Using β-NaGdF4:Eu instead of Eu(III) tri-(2,6-pyridine dicarboxylic acid) and europium fluoride in the diamond matrix resulted in enhanced signal/noise ratio in the luminescence. The mapping of the spatial distribution of photoluminescence intensity on macro- and micro scale revealed highly uniform emission originated from the composite. The developed composite material with mechanically strong, highly thermally conducting and transparent diamond matrix opens a way to use the diamond–fluoride composites as photo- and X-ray luminescent screens (scintillators) capable to withstand high photon fluxes.

Characteristic dimensions and evolution times of regions of secondary electronic excitations created by the interaction of ionizing radiation with matter cannot be measured directly. At the same time these are essential parameters both for engineering of nanostructured composite materials defining optimal layer thickness and nanoparticles radii and for the development of optimized scintillators. The paper demonstrates how such spatial and temporal data can be extracted from luminescence decay kinetics excited by vacuum ultraviolet (VUV) and X-ray photons at modern sources of synchrotron radiation MAX IV and PETRA III. Specific features of energy-band structure of self-activated crystal CeF3 are discussed, and its potential for a super-fast detection of ionizing radiation evaluated. Diffusion-controlled dipole–dipole interaction of Frenkel excitons is demonstrated to account well for the luminescence non-exponential decay kinetics providing information on the scales of excited regions created by photons of different energy. For 20 eV photons the radius of excited regions is estimated to be 10 nm, and for 200 eV photons it increases to 18 nm. Effective radius of excited regions of complicated shape created by 19 keV is as large as 80 nm and the diffusion length of Frenkel excitons over radiative time is 14 nm.

Metal hydrides and their alloys are widely used in nuclear power engineering and are regarded as promising hydrogen accumulators. Due to the nature of materials used in reactors, nondestructive methods are required to determine the concentration of hydrogen and its content in hydrides under the influence of a harsh environment. In this paper, a technique based on nuclear backscattering spectrometry is proposed, which allows determination of the hydrogen content in a sample at a depth of up to 100 μm. The profiles of the hydrogen distribution in Al, Mg, Ti, Zr, and their hydrides are measured. Estimation of the radiation damage to the sample is performed using the example of polymer impregnation of the protective coating.

Single-phase powders of Ba4Y3F17:Yb:Pr solid solutions with an average agglomerate size of 400 nm were synthesized by co-precipitation from aqueous solutions. It was shown that the down-conversion mechanism in the investigated samples was quantum cutting, with one photon absorbed by Pr3+ ions resulting in two photons emitted by Yb3+ ions. At first, overall the external quantum yield of down-conversion luminescence measured appeared to be relatively high, with a maximum value of 2.9 % for the Ba4Y3F17:Pr(0.1 %): Yb(10 %) sample. It makes this compound promising for Si-based solar cells efficiency enhancement.

Silicon nanocrystals in silicon nitride matrix are fabricated by thermal annealing of SiNx/Si3N4 multilayered thin films, and characterized by transmission electron microscopy, X-ray reflectivity and diffraction analysis, photoluminescence and X-ray photoelectron spectroscopy techniques. Si nanocrystals with a mean size of about 4 nm are obtained, and their properties are studied as a function of SiNx layer thickness (1.6–2 nm) and annealing temperature (900–1250 °C). The effect of coalescence of adjacent nanocrystals throughout the Si3N4 barrier layers is observed, which results in formation of distinct ellipsoidal-shaped nanocrystals. Complete intermixing of multilayered film accompanied by an increase of nanocrystal mean size for annealing temperature as high as 1250 °C is shown. Near-IR photoluminescence with the peak at around 1.3–1.4 eV is detected and associated with quantum confined excitons in Si nanocrystals: Photoluminescence maximum is red shifted upon an increase of nanocrystal mean size, while the measured decay time is of order of microsecond. The position of photoluminescence peak as compared to the one for Si nanocrystals in SiO2 matrix is discussed.

Древности Восточной Европы, Центральной Азии и Южной Сибири в контексте связей и взаимодействий в евразийском культурном пространстве (новые данные и концепции) Antiquities of East Europe, South Asia and South Siberia in the context of connections and interactions within the Eurasian cultural space (new data and concepts) К

Solid solutions LuxY1-xPO4 doped with Eu3+ were synthesized by the sol-gel method. Luminescence spectra under UV and X-ray excitation and luminescence excitation spectra in the UV-VUV energy range are presented. Observed variations of the structure of 4f-4f Eu3+ lines with the composition of the solid solution are explained by the fluctuations in the distribution of substitutional cations. The role of electronic structure modification in the fundamental absorption region with changing Y/Lu ratio is discussed and is suggested as the origin of different efficiency of energy transfer to Eu3+ in this region. Temperature dependence of the luminescence yield is related to the competition between emission centers and traps.