Needle-like Cs2Mo7O22 (7×1×1 mm) and plated Cs2Mo5O16 (4×3×2 mm) crystals were obtained by spontaneous crystallization method from Cs2Mo5O16 + 2

Bulk Na6Mo11O36 single crystals with dimensions 70*40*20 and 70*40*40 mm3 were obtained by the low-thermal gradient Czochralski technique. The uniformity of the grown boules was assessed using the following characterization techniques: X-ray diffraction (XRD) and differential scanning calorimetry. The crystal structure was thoroughly examined through single-crystal X-ray diffraction (SCXRD). Space group was determined by SCXRD as C2/c (a = 7.2229(1) & Aring;, b = 17.8065(4) & Aring;, c = 22.2789(5) & Aring;, beta = 90.311(1)degrees). Na6Mo11O36 crystals exhibited a strong tendency to formation of twins up to the change of crystallization direction on 90 degrees during the growth process, which is a unique event for Czochralski technique crystal growth. Crystal faceting was studied, and Miller indexes of developed facet families were determined by the XRD method; a reference model of the Na6Mo11O36 crystal was visualized based on obtained data. Optimal growth direction for obtaining uniform bulk Na6Mo11O36 crystals was determined to be [010]. Photoluminescence was registered on a 10 x 10 x 10 mm3 sample from 175 K temperature and below.

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.

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.

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.

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.

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).

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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TbGa3(BO3)4 crystals were grown using the Bi2Mo3O12: B2O3 : Tb2O3 flux, which decreases contamination of Bi in the resulting crystal. The produced compound crystallizes in the R32 space group with unit cell parameters: a= 9.4512(4) Å, c=7.4532(2) Å. A strong green emission of the luminescence is primarily dominated by the 5D4 to 7F5 transition in Tb3+. Annealing these crystals in a hydrogen atmosphere at 800°C causes a reduction in the luminescence efficiency. On the other hand, annealing in air results in the increment of QY up to the value of 38%.

The Sr3B2O6-YbBO3 diagram was constructed based on samples obtained by the solid-state synthesis. In the system YbBO3, Sr3Yb(BO3)3, Sr3Yb2(BO3)4 and Sr3B2O6 phases were identified by XRD analysis. Diffusion experiments showed formation of solid solutions between all compounds. These solid solutions demonstrate typical near-infrared luminescence in the range of 960–1020 nm, characteristic of Yb3+ and related to 2F5/2→2F7/2 transitions in ytterbium ions.

Transparent Li4Mo5O17 crystals with dimensions 60 x 30 x 20 mm were grown by low-thermal-gradient Czo-chralski technique. Optimal growth parameters were determined. According to SCXRD, Li4Mo5O17 compound crystallizes in the triclinic space group of P 1 and the unit cell parameters at 150 K are a = 6.7596(2) angstrom, b = 9.4546(3) angstrom, c = 10.7909(3) angstrom, alpha = 73.1610(10)degrees, 8 = 88.8810(10)degrees, gamma = 69.7460(10)degrees, V = 616.75(3) angstrom 3. Uniformity of obtained crystals was confirmed by XRD analysis. Li4Mo5O17 crystal structure and cell parameters were studied by SCXRD. Li4Mo5O17 melting point at 546 degrees C was determined by DSC curve in 300-1000 K range. Luminescence was registered with peak maximum 670 nm at 370 nm excitation and 645 nm at 300 nm excitation.

Na2Mo2xW2(1 − x)O7 (x = 0..1 with step 0.1) compositions were obtained by solid-state synthesis and spontaneous crystallization. The sample series were studied by XRD, Raman, DSC and SEM methods. The obtained data indicates formation of solid solutions, with unit cell gradually increasing with increasing tungsten ratio. A refined Na2Mo2O7 - Na2W2O7 phase diagram with unlimited miscibility was constructed. The solidus line was built based on DSC data and the liquidus line was constructed based on spontaneous crystallization experiments data. A luminescence study showed possibility of emission color variation in Na2Mo2xW2(1 − x)O7 solid solutions in dependence from excitation wavelength.

The TbBO3-GaBO3 phase diagram was investigated. The system was found to comprise solid solutions based on TbGa3(BO3)4, TbBO3 and GaBO3 compounds. The Bi2Mo3O12–based flux was employed to obtain single crystals of TbGa3(BO3)4 through spontaneous crystallization. The SCXRD analysis indicates that the obtained crystals belong to the R32 space group, with the unit cell parameters a = 9.453(2) Å and c = 7.453(2) Å. The green luminescence observed in all samples, with the exception of those containing undoped GaBO3, was found to be correlated with the 5D3→7F6 electron transition of Tb3+. The potential of TbGa3(BO3)4 crystals for various non-linear optical (NLO) applications was demonstrated by their second-harmonic generation (SHG) efficiency (deff), which was found to be 2.35 times higher than that of KDP crystals.

$\mathrm{TbGa}_{3}\left(\mathrm{BO}_{3}\right)_{4}$ and $\mathrm{TbAl}_{3}\left(\mathrm{BO}_{3}\right)_{4}$ crystals were grown using the $\mathrm{Bi}_{2} \mathrm{Mo}_{3} \mathrm{O}_{12}: \mathrm{B}_{2} \mathrm{O}_{3}: \mathrm{Tb}_{2} \mathrm{O}_{3}$ and $\mathrm{K}_{2} \mathrm{Mo}_{3} \mathrm{O}_{10}: \mathrm{B}_{2} \mathrm{O}_{3}: \mathrm{Tb}_{2} \mathrm{O}_{3}$ flux, respectively. The produced compounds crystallize in the R32 space group. A strong green emission of the luminescence is primarily dominated by the ${ }^{5} \mathrm{D}_{4}$ to ${ }^{7} F_{5}$ transition in $\mathrm{Tb}^{3+}$. According to the data obtained, the SHG efficiency is higher for the $\mathrm{TbGa}_{3}\left(\mathrm{BO}_{3}\right)_{4}$ compound due to its higher molar mass.

KSrY(BO3)(2): Tb3+ and Tb4+ solid solutions have been obtained using the solid-state synthesis and top-seeded solution growth method from the KF flux. Comparing the two types of Tb spectra 3d(3/2) TbO2 (Tb4+) and Na3Tb(BO3)(2) (Tb3+) with annealing in air of the KSrTb(BO3)(2) crystal, X-ray photoelectron spectroscopy (XPS) revealed that the crystal contains about 15% of Tb4+. The entire Y/Tb series has polymorphic phase transitions that occur at temperatures between 550 and 600 degrees C. Synthesis and subsequent treatment methodology have an impact on the resulting Tb3+/Tb4+ ratio in the sample. The best luminescent properties were measured on the composition KSrY0.9Tb0.1(BO3)(2), which was annealed at 700 degrees C under a hydrogen flow and cooled slowly.

TbAl3(BO3)4 should not be considered as a strictly stoichiometric compound. A variety of Tb1+xAl3-x(BO3)4 (x = -0.1-0.15) single phase compositions with the R32 space group were synthesized in the TbBO3-(Al2O3B2O3) system. The K2Mo3O10-B2O3-Al2O3 flux was used to grow Tb1+xAl3-x(BO3)4 (x = 0.06 and 0.09) crystals. The orthoborates have typical luminescence in the green range which correlated with the 5D3 -> 7F6 electron transition of Tb3+. However, deviating from stoichiometry can result in halving the quantum efficiency of luminescence. The SHG efficiency from 1064 nm radiation for Tb1+xAl3-x(BO3)4 crystals (x = 0.06 and 0.09) was found to be 1.82 and 1.53 times higher than that of KDP, respectively.