Here the NaF-B2O3-Li2O-MoO3 system is studied by delineating regions of primary crystallization of lithium borates in the LiB3O5-NaF-Li2Mo4O13 and LiB3O5-NaF-Li4Mo5O17 ternary sections. Lithium triborate crystals are obtained from the solvent based on NaF-Li4Mo5O17. The addition of NaF to the melt-solution system has been shown to increase both viscosity and crystal yield.

Here the NaF–B 2 O 3 –Li 2 O–MoO 3 system is studied by delineating regions of primary crystallization of lithium borates in the LiB 3 O 5 –NaF–Li 2 Mo 4 O 13 and LiB 3 O 5 –NaF–Li 4 Mo 5 O 17 ternary sections. Lithium triborate crystals are obtained from the solvent based on NaF–Li 4 Mo 5 O 17 . The addition of NaF to the melt–solution system has been shown to increase both viscosity and crystal yield.

In this work a series of sulfide reference materials based on synthetic pyrrhotite was obtained. 18 trace elements at a concentration level of 100 ppm were measured with a probe laser with diameters of 40, 65 and 80 mu m. Dependences of concentration and homogeneity (RSD) on temperature and duration of annealing were established. For the best sample prepared by annealing at 800 degrees C for 9 days the relative standard deviation below 5 % (laser spot size 80 mu m) for most elements except As, Se was achieved. However, further research is required to address the issues in the context of the high quality sulfide reference material. Among them are differences of estimated and calculated concentrations, variations of concentrations and RSD for different spot sizes and the loss of volatile components.

В настоящей работе была исследована тройная система BaB2O4-NaBaBO3-BaMoO4 для оптимизации процесса выращивания кристаллов метабората бария (β-BaB2O4), которые являются перспективными материалами для нелинейной оптики в видимом и ультрафиолетовом диапазонах. Основное внимание уделено изучению фазовых равновесий и характеристик кристаллизации в этой системе. Показано, что добавление молибдата бария снижает вязкость раствора-расплава, увеличивая выход и качество кристаллов. Методами твердофазного синтеза, дифференциальной сканирующей калориметрии (ДСК) и рентгенофазового анализа (РФА) определены ключевые параметры, и области первичной кристаллизации β-BaB2O4. Проведены эксперименты по выращиванию спонтанных кристаллов β-BBO. Полученные результаты демонстрируют перспективность использования составов данной системы в качестве растворителей для роста кристаллов β-BBO.

The present study concerns the Li2O-B2O3-MoO3-LiF system. LiB3O5 and Li3B7O12 crystals were obtained spontaneous crystallisation and TSSG. The addition of LiF to the molybdate flux represents a promising avenue for the growth of lithium borate crystals.

Using in situ X-ray photoelectron spectroscopy under ultra-high vacuum conditions, the adsorption of a thin tin layer (~1 monolayer $\approx 0.2$ nm) on the $\mathbf{Bi}_{2}\mathbf{Se}_{3}(0001)$ surface at room temperature followed by annealing at 21 $0\ {}^{\circ} \mathbf{C}$ was investigated. Changes in the X-ray photoelectron spectra of $\mathbf{Bi}_{2}\mathbf{Se}_{3}$ and $\mathbf{Sn}^{0}$ revealed the formation of crystalline bismuth and Sn-Se compounds indicating the substitution of bismuth atoms by tin, subsequent exit to the surface, and the formation of Bi(111) bilayers during annealing. Scanning electron microscopy in backscattered and secondary electron detection modes has visualized a labyrinth-like structure where regions with an enhanced tin concentration occupy approximately 50% of the sample area, which suggests the formation of $\mathbf{SnSe}_{2}$ and $\mathbf{SnSe}$ compounds in the near-surface region. Atomic force microscopy images of the $\mathbf{Bi}_{2} \mathbf{Se}_{3}(0001)$ surface morphology after the deposition and annealing of 1 monolayer of tin show height variations corresponding to $\mathbf{SnSe}_{2}$ and $\mathbf{SnSe}$ van der Waals molecular layers and the Bi(111) bilayers.

The YbBO3–ScBO3 system was studied across the selected compositional range by means of solid-state synthesis, powder X-ray diffraction (XRD), differential scanning calorimetry (DSC), and photoluminescence spectroscopy. XRD of annealed samples at 1300–1400 °C revealed that the system reaches equilibrium and consists of two phases, YbBO3 and ScBO3, separated by a two-phase region. The lattice parameters show a limited solubility between Yb3+ and Sc3+ ions. DSC measurements display a broad endothermic feature at approximately 1480 °C, corresponding to the eutectic point. Near-infrared emission excited at 975–980 nm originates from Yb3+ ions and shows the highest intensity for pure YbBO3 and for the Sc-rich composition, while intermediate samples exhibit weaker luminescence.

Phase pure Tb1-xYbxAl3(BO3)4 (x=0-1) crystalline powders were prepared by the combustion synthesis method. Down-conversion experiments under UV excitation of 375 nm revealed optimal concentration of Yb x=0.5 providing intensive green luminescence with 24% of quantum efficiency. Also up-conversion luminescence via energy transfer from Yb3+ to Tb3+ using a low power IR diode laser operating at 980 nm was achieved. Here the most powerful green emission was obtained with x=0.1.

Using angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT), an experimental and theoretical study of changes in the electronic structure (dispersion dependencies) and corresponding modification of the energy band gap at the Dirac point (DP) for topological insulator (TI) Mn_1-xGe_x Bi_2 Te_4 have been carried out with gradual replacement of magnetic Mn atoms by non-magnetic Ge atoms when concentration of the latter was varied from 10% to 75%. It was shown that when Ge concentration increases then the bulk band gap decreases and reaches zero plateau in the concentration range of 45%-60% while non-topological surface states (TSS) are present and exhibit an energy splitting of 100 and 70 meV in different types of measurements. It was also shown that TSS disappear from the measured band dispersions at a Ge concentration of about 40%. DFT calculations of Mn_1-xGe_x Bi_2 Te_4 band structure were carried out to identify the nature of observed band dispersion features and to analyze a possibility of magnetic Weyl semimetal state formation in this system. These calculations were performed for both antiferromagnetic (AFM) and ferromagnetic (FM) ordering types while the spin-orbit coupling (SOC) strength was varied or a strain (compression or tension) along the c-axis was applied. Calculations show that two different series of topological phase transitions (TPTs) may be implemented in this system depending on the magnetic ordering. At AFM ordering transition between TI and trivial insulator phase goes through the Dirac semimetal state, whereas for FM phase such route admits three intermediate states instead of one (TI - Dirac semimetal - Weyl semimetal - Dirac semimetal - trivial insulator).

The formation of solid solutions in the CaMoO4-CaWO4 binary system is investigated by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy methods. The intermixtures of CaMoO4 and CaWO4 components are sintered in 600-1200 degrees C temperature range (in 100 degrees C increments). The solidus of the CaMoxW(1-x)O4 system is studied by the differential scanning calorimetry method in the x = 0.3 & mldr; 1.0 range. CaMoO4-CaWO4 phase diagram is constructed up to 1550 degrees C. The minimal sintering temperature in order to get CaMoxW(1-x)O4 solid solution is shown to be 800 degrees C. Cathodoluminescence study of CaMoxW(1-x)O4 compounds showed higher intensity of molybdate luminescence type.

This study investigates methods for controlling the physical properties of the intrinsic magnetic topological insulator MnBi_2Te_4 (MBT) by substituting Mn with Pb in Mn_1-xPb_xBi_2Te_4 (MPBT) solid solutions. This substitution enables tunable magnetic and electronic properties. Using various angle-resolved photoemission spectroscopy (ARPES) techniques, including spin-resolved and circular dichroism (CD) measurements, we analyzed the evolution of the electronic structure across different Pb concentrations, with a focus on topological phase transitions (TPT) near x = 50 TPT include the presence or absence of topological surface states (TSS) and bulk band gap closure. The results show a gradual decrease of the bulk band gap in the electronic structure of MPBT up to x = 40 followed by a constant gap value between 40 - 60 a PbBi_2Te_4-like electronic structure. TSS were observed at x less than 30 were absent near x = 55 semi-metallic or a trivial insulator with a narrow gap phase. These findings demonstrate the tunability of the electronic structure of MPBT, making it a promising candidate for topological and spintronic applications.

Introduction. Borates of rare earth elements attract attention due to their unique physical properties due to the peculiarities of their electronic structure and crystal lattice. Ytterbium orthoborates are of great practical importance in the field of infrared luminescence. The aim of the work. Investigation of the structure, phase composition and luminescent properties of GaBO3-based solid solutions doped with ytterbium ions. Methodology. Ga1-xYbxBO3 (x = 0, 0.005, 0.01, 0.02, 0.03, 0.05, 0.06 and 1) were obtained by solid-phase synthesis. Results and discussions. SEM EDS analysis showed that 1 mol.% Yb dissolves in GaBO3 at a temperature of 700°C and 2 mol.% Yb at temperatures of at 800 and 900°C. The results of diffusion experiments indicate that the maximum is 2 mol.% of Yb ions can be dissolved in gallium borate. These data are consistent with the results of X-ray phase analysis, showing that the ytterbium content is over 2 mol.%, significant impurities and signs of incomplete synthesis are observed. Conclusion. The Ga0.995Yb0.005BO3 and Ga0.99Yb0.01BO3 compounds exhibit stable luminescent properties with broad peaks at 919 nm and 970 nm. These results highlight the potential of the materials for applications in optoelectronics and photonics.

The optical properties of new three-cation crystals family RE x Nd y Sc z (BO3)4 (RE:NSB), where RE are Sm - Lu lanthanides and x + y + z = 4, have been studied. The influence of the cation RE on the absorption and luminescence spectra of crystals was determined. The effective nonlinearity coefficient of crystals for second harmonic generation (SHG) of Nd:YAG laser radiation (1064 nm, 7 ns) was estimated using the Kurtz-Perry powder method. It is established that for the RE:NSB series, the highest luminescence intensity and SHG efficiency is demonstrated by the Gd:NSB crystal. It may be promising as active medium of self-frequency doubling solid-state lasers.

A wide range of solid solutions based on TbBO3 (with ScBO3 ≤ 30 mol%) and ScBO3 (with TbBO3 ≤ 50 mol%) was found in the TbBO3–ScBO3 system. Under UV excitation the characteristic green emission is visible due to the typical 5D4–7F5 transition of Tb3+. The intensity of photoluminescence significantly depends on the doping concentration of Tb3+ and the optimal concentration has been determined as x = 0.05. Crucial impact of hydrogen treatment on the luminescent properties was found. The compositions of TbxSc1–xBO3 (x = 0.05–0.1), after being treated with hydrogen at a temperature of 800 °C, has high potential for practical application as a green phosphor. This is due to its impressive quantum yield value of up to 69 % when excited by a 378 nm.

Using angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT), an experimental and theoretical study of changes in the electronic structure (dispersion dependencies) and corresponding modification of the energy band gap at the Dirac point (DP) for topological insulator (TI) $\mathrm{Mn}_{1-x} \mathrm{Ge}_x \mathrm{Bi}_2 \mathrm{Te}_4$ have been carried out with gradual replacement of magnetic Mn atoms by non-magnetic Ge atoms when concentration of the latter was varied from 10$\%$ to 75$\%$. It was shown that when Ge concentration increases then the bulk band gap decreases and reaches zero plateau in the concentration range of 45$\%$-60$\%$ while non-topological surface states (TSS) are present and exhibit an energy splitting of 100 and 70 meV in different types of measurements. It was also shown that TSS disappear from the measured band dispersions at a Ge concentration of about 40$\%$. DFT calculations of $\mathrm{Mn}_{1-x} \mathrm{Ge}_x \mathrm{Bi}_2 \mathrm{Te}_4$ band structure were carried out to identify the nature of observed band dispersion features and to analyze a possibility of magnetic Weyl semimetal state formation in this system. These calculations were performed for both antiferromagnetic (AFM) and ferromagnetic (FM) ordering types while the spin-orbit coupling (SOC) strength was varied or a strain (compression or tension) along the $c$-axis was applied. Calculations show that two different series of topological phase transitions (TPTs) may be implemented in this system depending on the magnetic ordering. At AFM ordering transition between TI and trivial insulator phase goes through the Dirac semimetal state, whereas for FM phase such route admits three intermediate states instead of one (TI - Dirac semimetal - Weyl semimetal - Dirac semimetal - trivial insulator).

Solid solutions based on (Eu,Gd)Sc3(BO3)4 , Gd)Sc 3 (BO 3 ) 4 (C2/c) and Gd 0.25 Sc 0.75 BO 3 (R R 3) in the EuSc3(BO3)4-GdSc3(BO3)4 3 (BO 3 ) 4-GdSc 3 (BO 3 ) 4 system were studied. Synthesis at 1250 degrees C provides wide homogeneity regions which are stable at room temperature. Melt-solution crystallization of both compounds from LiBO2-LiF 2-LiF flux was shown. All the obtained samples have luminescence characteristic of Eu3+ 3+ with a largest peak at 615 nm corresponding to the 5 D 0 -> 7 F 2 transition. In this series the luminescence intensity monotonically increases with an increase of Eu content. The largest quantum yield of luminescence (53 %) in the EuSc3(BO3)4-GdSc3(BO3)4 3 (BO 3 ) 4-GdSc 3 (BO 3 ) 4 system is demonstrated by EuSc3(BO3)4 3 (BO 3 ) 4 sample.

The phase diagram of the Sr3B2O6-NdBO3 binary system was studied. The intermediate compound Sr3Nd2(BO3)(4) can be synthesized over a wide range of compositions, from 27 to 70 mol.% NdBO3 , at 1200(degrees)C The maximum luminescence of Nd in this solid solution was measured for the highest content of Sr. The partial substitution of Nd by 3 mol.% Sr in NdBO3 does not significantly affect the presence of concentration quenching. The phase exhibiting the strongest luminescence within the system is neodymium doped Sr(3)B2O(6).

The surface preparation of topological insulators (TIs) is a critical task in order to realize their efficient applications. A chemical treatment in an anhydrous solution of hydrogen chloride in isopropanol (HCl-iPA) and a subsequent annealing at relatively low temperature in ultrahigh vacuum (UHV) was successfully used for the surface preparation of bulk 3D (0 0 0 1) TIs Bi2Te3, Sb2Te3, Bi2Se3 and an MBE - grown Bi2-xSbxTe3-ySey (BSTS) thin films. The surface treatment showed a significant modification of the initial TI surfaces, which was free from the structural disorder, oxidation and chemical impurities determined by X-ray photoelectron spectroscopy and low-energy electron diffraction. The insulating nontrivial bulk gap and well resolved gapless surface states with a linear dispersion of a massless Dirac cone were observed by angle-resolved photoelectron spectroscopy (ARPES). In the BSTS film, the Fermi level is located within the bulk band gap. The negative magnetoconductance corresponding to weak antilocalization demonstrated the contribution of the surface states of BSTS, that promise to be protected from backscattering. The surface treatment method proposed in this work is highly efficient for both bulk and thin TI films that can be useful for the deposition of an insulators/metals to fabricate transistor and spin valve systems.

A series of novel KSrY1–x Er x (BO3)2 (x = 0–1) phosphors that emit near-infrared radiation was synthesized using solid-state methods. Pure Y and Er crystals were grown using a KF flux via the top-seeded solution growth technique. In situ high-temperature single crystal X-ray diffraction, Raman spectroscopy and DFT calculations were used for characterization. Within the series, a polymorphic phase transition from space group P21/m to R 3 m was discovered between 550 and 600°C. The concentration dependence of the luminescence intensity was measured for the samples. A strong emission of Er3+ electron transition 4I13/2 → 4I15/2 was detected within the 1529–1549 nm range, with the maximum observed for the KSrY0.4Er0.6(BO3)2 composition.

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