This work investigates the luminescent properties of fluorapatite doped with Tb3+ ions (HAp–F:Tb) to determine the nature of the luminescent centers and the excitation features. Biohydroxyapatite was obtained from cattle bone raw material by rapid pyrolysis followed by annealing at 750°C; doping was carried out by the solvation–precipitation method. The samples were characterized by X-ray diffraction analysis, IR spectroscopy, and photoluminescence spectroscopy in the 200–700 nm range. It was established that the main active center is Tb3+ : intense emission bands corresponding to the 5D4 → 7F5 , 5D4 → 7F4 , and 5D4 → 7F3 transitions were recorded in the 490–620 nm region. The maximum intensity was observed under excitation at 220–260 nm and 355–377 nm, indicating direct excitation of Tb3+ and/or energy transfer from the matrix and defect levels. The obtained results demonstrate the promise of HAp–F-Tb as a luminescent material and the possibility of targeted modification of its optical properties through doping with rare-earth ions.
The photocatalytic degradation of paracetamol, a widely detected pharmaceutical contaminant, was investigated using WO3 nanopowders synthesized via a hydrothermal method. The obtained materials exhibited a hierarchical micro/nanostructured morphology composed of interconnected grains and well-defined nanoplate-like particles. Optical characterization revealed an indirect band gap of approximately 2.9 eV. The photocatalytic performance of WO3 was evaluated under light irradiation, demonstrating a gradual decrease in paracetamol concentration with increasing irradiation time. The degradation process followed pseudo-first-order kinetics, with an apparent rate constant ( kapp ) of 2.54 * 10-2 min -1 . The enhanced photocatalytic activity is attributed to the developed surface morphology and improved charge transport within the interconnected structure. These results highlight the potential of WO3 nanopowders as effective photocatalysts for the removal of pharmaceutical pollutants from aqueous environments.
A process for the purification and growth of alkali halide crystals (AHCs) has been demonstrated using the KCl:Li crystal as a representative example. The experiments were performed on an experimental crystal growth setup manufactured by Across International (USA). The procedure comprised the following sequential stages: (i) establishment of a deep static vacuum ( 10^-3 Pa or 10^-6 Torr) within a quartz reactor containing a quartz ampoule with a raw material; (ii) introduction of high-purity argon at room temperature to a pressure of 0.3–0.5 bar, calculated to reach 1.1–1.3 bar at the melt temperature of the material (770–800°C), in order to suppress the evaporation of aggressive halogen vapors. Crystal growth was conducted in strict accordance with the protocol of the Eurotherm system and the MCGS (Monitor and Control Generated System) human–machine interface (HMI) platform. Owing to this integrated control architecture, a controlled slow-cooling regime of the “superheated” crystal at a rate of 20–30 °C/h was implemented, a capability not previously attainable in comparable crystal growth systems. The newly developed integrated crystal growth system differs fundamentally from conventional designs and does not require: (i) quartz-sealing laboratory facilities for ampoule sealing, since the raw material within the quartz ampoule is maintained under vacuum inside the quartz reactor; (ii) additional water cooling of the installation, as the crystallization center is formed close to the thermal block and ends of the quartz tube are positioned outside the high-temperature zone. In a test regime, X-ray luminescence (XRL) spectra of freshly grown KCl:Li crystals were recorded as a function of lithium ion concentration. The anticipated enhancement of the luminescence light yield was observed, attributed to the recombination assembly of electron–hole pairs within the field of lithium ions. The result constitutes an important parameter for the development of the scientific basis of scintillation detectors.
In experiments performed at GELINA (IRMM, Belgium) and IREN (FLNP JINR, Dubna, Russia) facilities, variations in the total kinetic energy (TKE) of fission fragments as a function of incident neutron energy were experimentally observed in the resonance region of 235U fission. These observations provided a basis to assume a correlation between the number of prompt fission neutrons and the TKE. To further investigate this dependence, the ENGREN setup was developed. It consists of a twin Frisch-gridded ionization chamber (GIC) with a target at its center, surrounded by 32 detectors based on EJ-309 liquid scintillator arranged in a spherical configuration around the GIC. The setup is designed for simultaneous measurement of the TKE and angular distributions of fission fragments, as well as for registration of prompt fission neutrons. We present its comprehensive calibration and performance validation. Energy calibration was performed by comparing measured gamma-ray spectra (22Na, 137Cs, 60Co) with Monte Carlo simulations, establishing a linear response ( R2 = 0.9977 ) and an energy resolution of ∆E/E = 7.7% at 1.333 MeV. The resolution parameters are consistent with the characteristics of organic liquid scintillators. Optimal neutron-gamma pulse shape discrimination (PSD) was achieved, with Figure of Merit (FoM) values matching standard specifications. The system’s readiness is demonstrated by a geometric efficiency of 4.55% and successful test measurements with a 235U target at the JINR IREN facility, confirming its capability for high-statistics fission studies.
Thermoelectric materials, an important class within the semiconductor family for energy conversion, have been extensively studied in bulk form. However, growing interest in nanoscale materials driven by the quantum confinement effect has made it increasingly important to investigate how their properties change at reduced dimensions. In this work, we demonstrate the successful fabrication of nanosized ternary van der Waals (vdW) compounds SnSb 2 Te 4 and GeBi 2 Te 4 from their high-quality single crystals using High Energy Ball Milling (HEBM) for the first time. Here we discuss the effect of milling variables, i.e., materials of the milling container or grinding vessel and balls, milling medium (wet vs. dry), milling time, etc. The scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) analysis of the fabricated nanopowders reveals a strong sensitivity of the samples to the grinding vessel and ball materials, which introduces significant contamination during the milling process. Upon the milling time, this contamination can significantly impact the final composition of the powder, which is undesirable for functional semiconductor materials, where electronic properties are highly sensitive to impurities. Using different types of milling equipment, we demonstrate that nanoscale refinement with minimal impurity can be achieved simply by selecting appropriate milling materials, without modifying the target material or using protective agents. This result is particularly valuable for the preparation of high-purity nanoscale thermoelectric materials based on single-crystalline layered vdW compounds by the top-down method.
In Dy-doped Y3Al5O12 garnets exposed to UV photons near the fundamental absorption region, the formation of composite electron–radiative states arising from both intrinsic and impurity-related electron–hole trapping centers has been studied. Under exposure with photons of 6.2 eV and 5.64 eV at 77 K, a new recombination emission in Y3Al5O12 –Dy has been observed for the first time at 3.05 eV and 2.92 eV, which is excited by photon energies of 3.85 eV and 4.45 eV at 77 K. On the basis of the obtained experimental data, it is assumed that during UV irradiation near the fundamental spectral region of the matrix, transfer of charge from oxygen in the Al5O12 anionic complex of the valence band to a neighboring anion leads to the formation of intrinsic electron trapping centers (Al5O12)3– + e– → (Al5O12)4– ; in a similar way, impurity electron trapping centers are formed: Dy3+ + e– → Dy2+ . The intrinsic and impurity electron trapping centers form combined electron–radiative local states below the conduction band. As the combined electron–radiative state decays, ionization of both intrinsic and impurity-related electron traps occurs. The released electrons then recombine with hole trapping centers (Al2O7)2– located near the ground state of Dy3+ ions. This process can lead to exciton formation, and the energy released during recombination is either transferred to the Dy3+ impurities or emitted as recombination radiation with energies of 3.05 eV and 2.92 eV.
As is known, synthesis of high-strength, stable lithium-containing ceramics capable of withstanding high mechanical loads during operation is one of the key problems in the field of materials science, the solution of which will determine the potential for using new lithium-containing ceramics for blankets. In the work, using the method of mechanical mixing and subsequent thermal annealing, samples of lithium-containing ceramics based on lithium aluminate were obtained, and the variation of the ratio of the components during mixing made it possible to obtain ceramic samples with different phase ratios, a change in which, according to the data obtained, leads to a change in the strength and mechanical properties of the ceramics. According to X-ray diffraction analysis and Raman spectroscopy data, it was found that variation in the ratio of components in the composition of lithium aluminate due to an increase in the proportion of aluminum oxide leads to the formation of glass phases, as well as transformations of the tetragonal phase LiAlO2 into the cubic LiAl5O8 with subsequent dominance of this phase in the composition at concentrations of 0.9 M Al2O3. Moreover, the analysis of optical spectra showed that the change in the phase ratio is accompanied by the formation of oxygen vacancies, the minimum density of which is observed for samples of single-phase ceramics with the tetragonal phase LiAlO2. The evaluation results of the mechanical properties of ceramics showed that the formation of two-phase ceramics containing the tetragonal phase LiAlO2 and the orthorhombic phase Li5AlO4 leads to higher hardness and crack resistance compared to single-phase LiAlO2 ceramics. At the same time, the formation of two-phase ceramics, including the cubic phase LiAl5O8, leads to less pronounced changes in resistance to external influences due to the presence of glass-phase inclusions in the structure.
