CsLaSiS4 single crystals doped with Tb3+ and co-doped with Ce3+, Tb3+ ions were obtained by a high- temperature flux synthesis. XRD data demonstrate that the samples crystallize in the orthorhombic P nma space group without additional reflections belonging to the impurity phases. Low-temperature luminescent spectroscopy methods have been used to study the efficiency of radiative transitions and energy transfer between Ce3+ and Tb3+ ions. Additionally, the effect of irradiation with protons with an energy of 18 MeV from a cyclotron was studied. Spectral-kinetic measurements of pulsed cathodo- and photoluminescence of samples co-doped with Ce3* and Tb3* revealed bidirectional energy transfer processes between these ions, the parameters of nonradiative energy transfer Ce3+ -> Tb3+ were determined. The effect of concentration quenching is observed in undoped CsTbSiS4. The method of low-temperature thermally stimulated luminescence and the kinetics of pulsed cathodoluminescence indicate a high concentration of "shallow" carrier trapping centers in doped samples. When irradiating CsLaSiS4:0.5%Ce sample with protons, both the low-temperature emission of self-trapped excitons (STE) and the energy transfer STE -> Ce3+ decrease, the luminescence yield of defect-bound excitons (DBE) also decreases compared to the emission of Ce3+ ions, and defects are mainly formed, which are the centers of nonradiative recombination of band charge carriers.

Ce+3 doped CsLaSiS4 single crystals were synthesized using high-temperature flux synthesis. XRD analysis showed that the products are isostructural to CsLaSiS4 and crystallize in orthorhombic space group Pnma. Absorption spectra were studied at room temperature, and photoluminescence properties were examined in the temperature range of 5-310 K. The energy of interband transitions E-g = 3.75 eV was determined at room temperature in the Tauc model. At room temperature, only a non-elementary d -> f emission band of Ce+3 ions was observed in the 520 nm region. The luminescence kinetics upon excitation by a pulsed cathode beam or X-ray synchrotron radiation exhibited a dominant nanosecond component. Decay time, as well as build-up time, decreased with increasing concentration of Ce+3 ions. Concentration quenching of Ce+3 emission was not observed up to 11.9 mol% of Ce+3 ions. At a low temperature of 5 K, new wide emission bands at 422 and 688 nm appeared in the photoluminescence spectrum. It is shown that the 422 nm band in the photoluminescence spectrum corresponds to host emission, specifically the luminescence of self-trapped excitons (STE). The 688 nm emission band corresponds to defect-related luminescence. STE emission is quenched according to the Mott law at temperatures above 26 K with an activation energy of 20 meV. An efficient energy transfer channel from the STE to the Ce+3 ion via the radiative resonance mechanism is observed. The emission of Ce+3 ions and defect-related luminescence can be excited by the intracenter way, due to electron-hole recombination, or by the creation of defect bound excitons. Based on the obtained spectroscopic data, a band scheme illustrating the processes of relaxation of electronic excitations at T = 5 K in Ce+3 doped CsLaSiS4 crystals is proposed.

A series of single crystals of CsLa1-& khcy;& Scy;& iecy;& khcy;SiS4 monophasic solid solution (x = 0-1) has been obtained for the first time by high-temperature flux synthesis. Methods of XRD and chemical analysis, absorption and low-temperature (from T = 5 K) luminescent spectroscopy were used. The results of the band scheme calculating using density functional theory correlate with spectroscopy data. One non-elementary d -> f emission band of Ce3+ ions is observed in the region of 520 nm in the luminescence spectra at room temperature at any value of the x parameter. The luminescence decay kinetics of Ce3+ ions upon excitation by a pulsed electron beam, X-ray synchrotron radiation or intracenter photoexcitation is characterized by a nanosecond component. As the parameter x increases, the decay time is reduced from 132 ns (x = 0.005) to 0.88 ns (x = 1). The luminescence decay kinetics upon photoexcitation at x = 0.005-0.12 is characterized by monoexponential decay with tau = 31.4 +/- 0.2 ns. Concentration quenching of the Ce3+ ion photoluminescence is not observed up to the value of the parameter x = 0.12; it only appears at x = 1. The anomalously short decay time of the Ce3+ ions luminescence in CsCeSiS4 upon both X-ray excitation and photoexcitation is associated with concentration quenching. At temperature 5 K, new intense bands at 408 and 688 nm in addition to the Ce3+ emission band observed in the photoluminescence spectra of nominally pure CsLaSiS4 or at the lowest parameter value x = 0.005. These bands correspond to the luminescence of self-trapped excitons (STE) and defects. With increasing x parameter, the STE emission band is reabsorbed by the absorption of Ce3+ ions and is quenched due to the resonance energy transfer STE -> Ce3+ center. Thermoluminescence glow curves of CsLa1-xCexSiS4 irradiated with X-ray at T = 90 K are characterized by several low temperature intense peaks, which indicates a high concentration of charge carrier traps.

Single crystals of a solid solution of the (Y 1– x Eu x ) 2 O 3 compound with the bixbyite-type structure and different europium contents, which are suitable for the structural analysis, are grown by the flux method. The structural data show that the Y/Eu occupation of independent sites is uniform in the crystal; europium has no preferred site occupancy. The average R –O distance is also typical of the rare-earth metal atoms located at different crystallographic sites and increases monotonically as the europium content increases in the crystal. The europium distribution coefficient from the flux is noticeably less than unity, which enriches the crystal with yttrium compared to the flux.

Large-sized, high optical quality Gd2O3 single crystals were grown from a solution at T = 1145 degrees C using Czochralski method. XRD analysis showed that the crystal structure is characterized by a single cubic (bixbyite) phase (c-phase). The absorption spectra and luminescence properties of Gd2O3 doped with Eu3+ and Tb3+ impurity ions were studied. The absorption spectrum of Gd2O3:Eu in the short wavelength region is mainly due to charge transfer transitions from O2-to Eu3+ (240-290 nm), which overlap with the Urbach tail of the host-absorption. Additionally, electronic transitions in Eu3+ (320-540 nm) and Gd3+ (245-315 nm) lanthanide ions contribute to the absorption spectrum. Intraconfigurational radiative f - f transitions in impurity ions are clearly observed upon both UV-and X-ray excitations. However, 6PJ & RARR; 8S7/2 radiative transitions in Gd3+ ions are completely unobservable. Based on the obtained spectroscopic data, the energy positions of the ground state of all di-and trivalent lanthanide ions, as well as the energies of intraconfigurational f - f and interconfigurational f - d electronic transitions in Gd2O3 crystals with a cubic structure, are calculated. The proposed electronic energy diagram is used to discuss efficient energy transfer between lanthanide ions.

We have perfected processes for the synthesis of lanthanum, gadolinium, and yttrium oxyselenides by heating oxides in flowing hydrogen and selenium vapor. The optimal selenidation temperature is 700°C for lanthanum, 850°C for gadolinium, and 900°C for yttrium. Subsequent annealing of the materials in flowing hydrogen at 1000°C makes it possible to remove trace levels of amorphous selenium and impurity phases containing diselenide groups.

X-ray quality crystals of solid solutions of complex borates Li6R(BO3)3 and LiR6(BO3)3O5 (R = Y, Eu) with different europium contents are grown from a Li6R(BO3)3 melt solution with an addition of 20 mol.

Методом роста из раствор-расплава были выращены монокристаллы твердого раствора соединения (Y1–xEux)2O3 со структурой биксбиита и разным содержанием европия, пригодные для структурного анализа. Структурные данные показывают, что распределение Y/Eu по независимым позициям в кристалле является равномерным, нет предпочтительного заполнения позиций европием. Среднее расстояние R-O в изученных кристаллов также близко для атомов редкоземельного металла, находящихся в разных кристаллографических позициях и монотонно растет с увеличением содержания европия в кристалле. Коэффициент вхождения европия из раствор-расплава заметно меньше единицы, что приводит к обогащению кристалла иттрием по сравнению с раствор-расплавом.

Из раствор-расплава Li6R(BO3)3 (R= Y, Eu) с добавлением 20 мол. % смеси оксидов иттрия-европия были выращены кристаллы твердых растворов сложных боратов Li6R(BO3)3 и LiR6(BO3)3O5 с разным содержанием европия, пригодные для структурного анализа. Структурные данные показывают, что распределение Y/Eu в LiR6(BO3)3O5 по независимым позициям в кристалле является неравномерным, различие в заселенности Eu достигает 80%. Это различие в заселенности коррелирует с объемом позиций, рассчитанным в структуре LiR6B3O14 по Хиршфельду.

We present here the syntheses and structural characterizations of inorganic polymeric cluster compounds, Cs[Mn(salen)](3)[{Mo6Br6Se2}(CN)(6)] (1) and (H3O)(TBA)[Mn(salen)](2)[{Mo6Br6Se2}(CN)(6)] (2) (TBA=tetrabutylammonium ((n-C4H9)(4)N+)), built-up from [{Mo6Br6Se2}(CN)(6)](4-) molecular building blocks and Mn(salen)(+) complexes (salen = salen = N,N '-bis(salicylidene)ethylenediamine). The nature of additional counter cations (i. e. Cs+ or TBA(+)) enables to control the interactions between the [{Mo6Br6Se2}(CN)(6)](4-) building blocks and the Mn(salen)(+) groups. Thus, 1 was obtained by slow diffusion of a methanol solution of K2Cs2[{Mo6Br6Se2}(CN)(6)] cluster compound into a methanol solution of Mn(salen)ClO4. 2 was obtained in a similar way but after the addition of tetrabutylammonium bromide into the solution of Mn(salen)ClO4. 1 is a bimetallic 3D coordination compound ( R3?c ${R\bar{3}c}$ ) and 2 is a bimetallic 2D compound ( P1? ${P\bar{1}}$ ). Structural correlations between 1 and 2 are discussed and compared with relevant examples found in the literature.

Large-size high optical quality Gd2O3 single crystals were grown from solution at T = 1145 degrees C by Czochralski method. XRD analysis showed that the crystal structure is characterized by a single cubic phase (C-phase). Absorption spectra and luminescence properties of Gd2O3 doped with impurity Tb3+ ion were studied. The absorption spectrum is determined by electronic transitions in Gd3+ ion (spectral region of 245-315 nm) and interband electron transitions below 240 nm. Intraconfigurational radiative f-f transitions from 5D4 level in Tb3+ ion are clearly manifested upon both UV-and X-ray excitation. At the same time, 6PJ & RARR; 8S7/2 radiative transitions in Gd3+ ions are completely absent. This fact indicates high efficiency of nonradiative energy transfer from Gd3+ to Tb3+ ions. Thermo-luminescent spectroscopy shows the absence of charge carrier trapping centers, which proves the perfection of its crystal structure. The crystal under study shows high radiation resistance to high-energy (E = 10 MeV, D = 105 kGy) electron beam. However, the effects of irradiation appear only in the photoluminescence excitation spectra and thermally stimulated luminescence.

Single crystals of a solid solution of the (Y1–xEux)2O3 compound with the bixbyite-type structure and different europium contents, which are suitable for the structural analysis, are grown by the flux method. The structural data show that the Y/Eu occupation of independent sites is uniform in the crystal; europium has no preferred site occupancy. The average R–O distance is also typical of the rare-earth metal atoms located at different crystallographic sites and increases monotonically as the europium content increases in the crystal. The europium distribution coefficient from the flux is noticeably less than unity, which enriches the crystal with yttrium compared to the flux.

Inorganic phosphors based on rare earth elements are commonly used as scintillation materials due to their high chemical and radiation resistance. In this work, we study gadolinium oxyselenide as a new phosphor material. The work describes a facile synthesis method for Gd2O2Se. Single crystal structure of this compound was determined for the first time: sp.gr. P3m1 with a = 3.8911(4) angstrom and c = 6.8829(8) angstrom. Gd2O2Se is stable in the inert atmosphere and melts at 2075 +/- 20 degrees C. This material is also stable when heated in air up to 720 degrees C. with the following oxidation and weight increase. This mass increase can be explained by the oxidation of Se2- to Se4+. Further temperature increase above 952 degrees C leads to a sharp mass loss and the final mass of sample corresponds to full oxidation of Gd2O2Se to gadolinium oxide. The band gap of the material was estimated to be 3.6 eV. Photoluminescence spectrum for Gd2O2Se:Tb3+ shows the characteristic transitions in Tb3+ ion with the most intense green emission that corresponds D-5(4) -> F-7(J) transitions.

Высокотемпературным синтезом были получены новые двойные тиосиликаты иттрия AYSiS4, A= Rb, Cs. Соединения кристаллизуются в ромбической сингонии (пр.гр. P212121) с параметрами: a = 6.3381(4) Å, b = 6.5961(4) Å, с = 16.8868(12) Å для RbYSiS4 и a = 6.3303(4) Å, b = 6.6593(5) Å, с = 17.5795(13) Å для CsYSiS4. Соединение с рубидием быстро гидролизуется водой, соединение с цезием устойчиво в сухом воздухе. Для CsYSiS4 методом диффузного отражения оценена ширина запрещённой зоны, составляющая 3.8 эВ. Спектр фотолюминесценции представляет собой широкую полосу в видимой области спектра с максимумом при λ = 492 нм (зеленая область). Времена жизни составляют τ1 = 5.25 мкс и τ2 = 0.26 мкс, с квантовым выходом < 1%.

Optical properties of doped optically pure rare-earth (RE) oxyselenides RE2O2Se:RE′ (RE = Gd, Y; RE′ = Sm, Tb) are studied. Photoluminescent properties of optically pure RE oxyselenides in the form of powders and thin films demonstrate the possibility in principle of using them as scintillation materials for detectors of ultraviolet or ionizing radiation.

By the high-temperature synthesis new double yttrium thiosilicates AYSiS4, A = Rb, Cs are obtained. The compounds crystallize in the orthorhombic system (space group P212121) with the following parameters: a = 6.3381(4) Å, b = 6.5961(4) Å, c = 16.8868(12) Å for RbYSiS4 and a = 6.3303(4) Å, b = 6.6593(5) Å, c = 17.5795(13) Å for CsYSiS4. The compound with rubidium is rapidly hydrolyzed by water; the compound with cesium is stable in dry air. For CsYSiS4 the band gap estimated by diffuse reflectance is 3.8 eV. The photoluminescence spectrum has a broad band in the visible region with the maximum at λ = 492 nm (green region). The lifetimes are τ1 = 5.25 µs and τ2 = 0.26 µs with the quantum yield of <1%.

The optical properties of doped oxoselenides of rare-earth elements of optical purity RE2O2Se:RE' (RE = Gd, Y; RE' = Sm, Tb) are studied. Photoluminescent properties of oxoselenides of rare earth elements of optical purity in the form of powders and thin films demonstrate the fundamental possibility of using them as a scintillation material for detectors of ultraviolet or ionizing radiation.