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A laboratory technique was developed for obtaining an ultra-low-background hybrid material based on organic glass — polymethyl methacrylate (PMMA). 157Gd nuclei are used as an efficient absorber of thermal neutrons in the hybrid material. A uniform distribution of gadolinium in the PMMAmatrix is achieved by introducing the gadolinium in the form of a coordination compound — gadolinium acetylacetonate — into the hybrid material. A uniform gadolinium distribution was achieved in a 5 cm thick matrix of hybrid material with gadolinium mass content from 1.0 to 1.5%. It is shown that at 298 K the mechanical characteristics of the hybrid material samples coincide with nominally pure PMMA, but at 77 K the hybrid material is inferior to pure PMMA within admissible requirements.

A method based on two-stage sublimation purification for obtaining high-purity tungsten (VI) oxide was developed. An impurity analysis of a commercial preparation of tungsten (VI) oxide was performed using mass spectrometry with inductively coupled plasma. Potassium-gadolinium-tungstate [KGW] crystals grown using commercial reagents and tungsten (VI) oxide with chemical purity of 99.999 wt.% were obtained. Acomparative analysis of crystals grown from different initial tungsten oxides was performed. It is shown that the developed high-purity tungsten (VI) oxide does not reduce the chemical purity of the grown KGWcrystals and is a promising raw material for the technology of glass-ceramic optical materials based on tungstates.

Transparent glass-ceramic materials co-activated by Eu3+/Gd3+ were obtained by heat treatment of the initial lead fluoroborate glasses. It was found that the rare-earth ions in the obtained transparent samples are located in nanoparticles of lead fluoride cubic crystals, distributed in the bulk of the glass. It was shown that Eu3+ ions are situated in a highly symmetric local environment and that the introduction of a second activator increases the nanocrystalline phase fraction.

The strong influence of MoO3 chemical purity from 99.99 wt% to 99.999 wt% for lithium triborate (LBO) and NaLa(MoO4)2 crystal growth as well as for OLED technologies has been demonstrated. The method of purification of molybdenum trioxide by vacuum sublimation under the controlled partial pressure of oxygen and with chemical bonding of residual tungsten has been developed. Numerical simulation of the technique processing allowed specifying the sublimation conditions and finding out the parameters, which defined optimal yeild of the condense phase. The experimental optimization of the parameters made it possible to purify crystalline α–MoO3 at least up to 99.9993 wt% when 65 elements were detected by inductevely coupled plasma mass-spectrometry.

Three NaGd(WO4)2 single crystals were grown by the Czochralski method using charges of different chemical purity. The impurity compositions of the grown crystals were analyzed by inductively coupled plasma mass spectrometry. The optical absorption spectra of the crystals were measured, and the effect of uncontrollable impurities on their optical properties and color was analyzed. The green color encountered in NaGd(WO4)2 crystals in some cases was shown to be due to the uncontrollable impurities of d elements, among which the chromium impurity had the most significant effect.

A laboratory technology for a new ultra-low background hybrid material (HM) which meets the requirements for neutron absorption with simultaneous neutron detection has been developed. The technology and hybrid material can be useful for future low background underground detectors designed to directly search for dark matter with liquid noble gases. The HM is based on a polymethylmethacrylate (PMMA) polymer matrix in which gadolinium nuclei are homogeneously distributed up to 1.5 wt% concentration in polymer slabs of 5 cm thickness. To determine the 65 impurity elements by the inductively coupled plasma mass-spectrometry (ICP-MS) technique in the Gd-based preparations in 100–0.01 ppb range, the corresponding method has been developed. Limits of determination (LD) of 0.011 ppb for uranium, and 0.016 ppb for thorium were achieved. An analysis of Gd raw materials showed that the lowest contents of U and Th (1.2–0.2 ppb) were detected in commercial Gd-based preparations. They were manufactured either from secondary raw materials (extraction phosphoric acid) or from mineral raw materials formed in sedimentary rocks (phosphogypsum). To produce the Gd-doped HM the commercial GdCl3 was purified and used for synthesis of low-background coordination compound, namely, acetylacetonate gadolinium (Gd(acac)3) with U/Th contents less than LD. When dissolving Gd(acac)3 in methylmethacrylate, the true solution was obtained and its further thermal polymerization allowed fabrication of the Gd-doped PMMA with ultra-low background.

The theoretical and experimental analysis of phase equilibria in the Zn–Se–Fe ternary system is carried out with the use of X-ray diffraction analysis and inductively coupled plasma mass-spectrometry. Information is acquired on monovariant equilibria in isothermal sections at temperatures of 730, 814, and 1073 K and also on the solubility of iron under conditions of bi- and monovariant equilibria at 1073 K. The phase composition of samples in the Zn–Se–Fe system synthesized at different temperatures and different total compositions is determined. The reliability of theoretically plotted isothermal sections in the Т–Х–Y projection of the P–T–Х–Y diagram for the Zn–Se–Fe ternary system is confirmed.

Aria is a plant hosting a$${350}\,\hbox {m}$$350mcryogenic isotopic distillation column, the tallest ever built, which is being installed in a mine shaft at Carbosulcis S.p.A., Nuraxi-Figus (SU), Italy. Aria is one of the pillars of the argon dark-matter search experimental program, lead by the Global Argon Dark Matter Collaboration. It was designed to reduce the isotopic abundance of$${^{39}\hbox {Ar}}$$39Arin argon extracted from underground sources, called Underground Argon (UAr), which is used for dark-matter searches. Indeed,$${^{39}\hbox {Ar}}$$39Aris a$$\beta $$β-emitter of cosmogenic origin, whose activity poses background and pile-up concerns in the detectors. In this paper, we discuss the requirements, design, construction, tests, and projected performance of the plant for the isotopic cryogenic distillation of argon. We also present the successful results of the isotopic cryogenic distillation of nitrogen with a prototype plant.

The products of interaction of SmF3 with metallic Sm0, Si, and molecular hydrogen in quartz, graphite, and molybdenum containers have been investigated by X-ray diffraction. It is shown that reduction occurs with the formation of nonstoichiometric cubic SmF2 + x (sp. gr. Fm3m, unit-cell parameter a = 5.8517(2) A) with a content x = 0.108 only in the case of synthesis of SmF3 with metallic Sm0 in a quartz ampoule. The transformation of the SmF2 + x phase composition in air at room temperature has been studied for the first time. It is found that SmF2.108 passes into the superstructural phase Sm13F32–δ (sp. gr. R3) with the unit-cell parameters a = 14.7354(4) A and c = 10.1156(4) A for 60 days. The use of Sm0, Si, and H2 as reducing agents for SmF3 is inefficient because of the weak tendency of the latter to reduction: the process occurs also with a low yield of the Sm13F32–δ phase and of the α-SmF3-based phase as impurity in the case of direct reduction by hydrogen.

A new approach for fabrication of laser elements in form of plates based on ZnSe:Fe2+ with undoped faces, combining the advantages of hot pressing and diffusion techniques has been proposed. CVD-ZnSe was used as a host material. 1 µm Fe film was deposited by electron-beam technique on one side of the polished CVD-ZnSe plate (20 mm in diameter and 2 mm in thickness). The elements were stacked in contact by iron surfaces, placed in a hot press-mold die, heated under vacuum to 1000 °C, exposed during 60 min with the application of 25 MPa uniaxial pressure. The iron film was dissolved in ZnSe matrix and elements welded together. The samples were subjected to hot isostatic pressing (HIP) during 29 h at 100 MPa argon pressure and 1300 °C. The influence of sintering and HIP processing conditions on local morphology and properties of the interface of welded elements was studied by SEM, TEM and optical microscopy. For all composite elements the lasing was obtained at a pumping by HF-laser at RT with high efficiency around 40%. The proposed technique removes restrictions on the size of laser elements and appears to be very promising for the management of the distribution profile of the doping component.

carry out the process of obtaining high-purity tellurium by the vacuum distillation method, a reactor design consisting of high-purity quartz glass and graphite is proposed. During the process, the tellurium melt evaporates; and the vapor is transferred from the hot part of the system to the colder one and condenses in the form of a solid phase (distillate) without the formation of a liquid. Regularities in the redistribution of impurities between the distillate and the cube stillage residue, as well as the spatial distribution of impurities in the distillate during the purification of metallic tellurium, are studied. It is established that some impurities, for example, s-metals, Zn, Ni, and V, and rare metals, are distributed uniformly along the length (20 cm) of the distillate. At the same time, Se tends to concentrate in the far (from the still) part of the distillate with a difference of more than one order of magnitude than in the near part.

A novel luminescent organic-inorganic hybrid material “LightSil” (hereinafter referred to as HM-LS) has been fabricated. Tris (8-hydroxyquinolate)aluminum (Alq3) purified by vacuum sublimation to 99.999 ​wt% was used as an organic phosphor. Silica aerogel was used as an inorganic matrix. Alq3 intercalation into aerogel structure did not strongly influence on the HM-LS morphology characteristics comparing with the pure aerogel, which indicated that the intercalation had proceed on the molecular level. An aerogel based hybrid was supercritical dried in a carbon dioxide environment under a pressure of 120 ​bar, at 40 ​°C at a carbon dioxide consumption of 500 ​g/h. The synthesis conditions (TEOS:2-propanol ratio) has been optimized to make the HM-LS sample with the best photoluminescence (PL) characteristics. Analysis of the PL spectra showed that the PL peak maximum of HM-LS shifted to longer wavelengths, and the HM-LS spectrum itself broadened by 64%: FWHMAlq3 ​= ​73 ​nm, FWHMHM-LS ​= ​113 ​± ​3 ​nm relative to Alq3 powder PL spectrum. The latter indicated on a change in the electronic structure of Alq3 in HM-LS in comparison with the nominally pure Alq3 and this proved the formation of a new hybrid material.

The method of growing of ZnS and ZnSe single crystals doped with chromium and iron using a combination of the solid phase recrystallization and diffusion doping during the high-temperature gas-static pressing has been implemented. The isostatic pressing up to 110 MPa has made it possible to increase the process temperature up to 1300 °C, increase the rate of grain growth and diffusion of Fe 2+ and Cr 2+ ions in zinc chalcogenides crystalline samples, reduce processing time to 25–150 h. ZnS:Cr (Fe) and ZnSe:Cr (Fe) single crystals from several to tens mm in size with dopant concentrations of (1–5)×10 19 cm −3 for Cr 2+ and (5–20)×10 18 cm −3 for Fe 2+ and at the total impurity's content no more than 5×10 −4 wt% have been obtained. The lasers made from the crystals demonstrated 55% differential lasing efficiency for the absorbed power.

Solid solution Li 2 Mo 1−X W X O 4 crystals were grown from two different melts (X=0.85 and 0.95) by Czochralski technique. The crystals were colorless and transparent within 300–1100 nm wavelength range. They had dimensions of 25 mm diameter and 100 mm length. The crystal grown from the X=0.85 melt had an inhomogeneous composition which varied from 0.65 to 0.88. The crystal grown from the X=0.95 melt had a uniform distribution of X, corresponding to the average Li 2 Mo 0.08 W 0.92 O 4 composition. Both crystals belong to a phenacite-type structure and they were characterized by X-ray diffraction, Raman and IR-spectroscopy.

The regularities of impurity distribution between the distillate and the still as well as the spatial distribution of impurities along the distillate length have been studied. We conclude that some impurities such as s−metals, Zn, Ni, V and rare metals distribute uniformly along the distillate length (20 cm). Contrarily, Se tends to concentrate in the distant (from the still) region of distillate with more than one order of magnitude higher concentration compared to the nearest region.

Three NaGd(WO 4 ) 2 single crystals have been grown by Czochralski technique using the initial chemicals with different purity. The optical absorption spectra of the crystals, as well as their impurity compositions have been measured. The possible reasons of the addition coloration of these crystals have been analyzed.

Hybrid organo-inorganic materials were prepared by solid-phase synthesis and by co-precipitation from aqueous solutions with phosphors — 8-hydroxyquinolates and diketonates of metals with hydrofluoric acid and ammonium fluoride. The photoluminescence spectra of the obtained hybrid materials were analyzed. A comparison was made with the spectral-luminescent properties of previously obtained hybrid materials by the melt technique using low-melting lead oxyfluoride glasses.

A technique for synthesis of high-pure tellurium oxide (IV) by chemical combustion of tellurium vapor in dry oxygen has been developed. The technique allows synthesizing crystalline β-TeO2 (paratellurite) free of OH-groups. Numerical simulation of the technique processing in a quartz-glass reactor let’s propose the mechanism of crystalline TeO2 formation as 2–5 μm particles and found out ranges of parameters of the combustion reaction of Te-vapor in oxygen atmosphere: temperature, tellurium vapor pressure, argon-carriage-gas flow, oxygen flow and total gas pressure in the reactor. The experimentally optimized parameters made it possible to synthesize crystalline β-TeO2 as pure as 99.999994 wt% (65 elements detected) using 99.997 wt% Te and 99.999 vol% oxygen with the yield of 85%.

The problem of obtaining crystalline ZnSe doped with d-elements for obtaining high-efficiency laser materials with characteristics in a wide IR range don’t possible successfully solved without reliable data on phase equilibrium and solubility of the components entering the system. The theoretical and experimental analysis of the three-component Zn—Se—Fe system for obtaining new fundamental information on phase using X-ray analysis (XRD) and inductively coupled plasma mass spectrometry (ICP-MS) was carried out. New experimental data of isothermal annealing in the ternary Zn—Se—Fe system at the temperatures 730 K (I, II), 814 K (III, IV), 1073 K (V), as well as information on Fe solubility in bi- and monovariant conditions by X-ray studies have shown the existence of the coexistence of the following phases: Fe3Zn10-Fe11Zn40-Zn-ZnSe (I), ZnSe-FeSe2-Fe7Se8 (II), ZnSe-Fe3Zn10-Fe (III), FeSe2-Fe7Se8-Se (IV), ZnSe-FeSe- Fe3Se4 (V), ZnSe-FeSe (VI) and confirmed the reliability of theoretical isothermal sections.

The glasses in PbF2–B2O3-REF3 (RE = Nd, Nd+La, Nd+Lu) system have been synthesized. The initial glasses were doped with several RE's (0.2–3.0 at%), one of which had no luminescent f–f transitions (La, Lu) and performed only the function of the stabilizer of the cubic phase PbF2, and the other (Nd) played the role of a luminescence center. Glass-ceramics have been obtained by the controlled crystallization of glasses with formation of Pb1-xLa/NdxF2+x or Pb1-xLu/NdxF2+x solid solutions. The luminescence spectra of co-activated glass-ceramics as well as crystalline samples demonstrated a splitting of the «0–0» line for the 4F3/2→4I9/2 transition. It has been shown that it is possible to stabilize a cubic phase based on PbF2 by several RE co-doping and to obtain glass-ceramics with a crystalline phase in which the concentration quenching was reduced compared to glass-ceramics doped with a single activator.

Lead fluoroborate and fluorosilicate glasses codoped with Nd3+/La3+, Er3+/Lu3+ and Er3+/Yb3+/Lu3+ - have been synthesized. Glass-ceramics have been made by heattreatment. In a glass-ceramic the rare-earth ions were located in fluoride crystal nanoparticles distributed in a glass. The changes in structural, mechanical and optical properties of the glassceramics were revealed in comparison with the initial glasses.

The melt structure evolution under the action of the low-frequency axial vibration control (AVC) technique was studied in situ by Raman spectroscopy for several complex chemical compound melts: sodium nitrate, margarine acid, paraffin mixture (C 17 -C 20 ). The measurements were conducted in the temperature range from the melting point up to 60 °C above. Comparison of crystallization heats for AVC activated and steady melts with melting heats of AVC-CZ and conventional CZ produced powders allowed to propose the energy diagram of NaNO 3 states for activated and non-activated melts and crystals based on DTA, XRD, DSC and Raman experimental data.

Tellurium oxide (IV) single crystals are in demand materials for manufacturing acousto-optical devices optical fibers for IR wavelength range. The initial material for production of active and passive optical materials must have purity better than 99.999 wt% and extremely low concentration of the residual water. The main method of synthesis of TeO2 is oxidation in nitric acid followed by recrystallization from HCl is complicated, also amount of used high purity acids and waste are very high. Besides the residual water content is no less than 10 ppm. In the research we have developed the procedure for the synthesis of high-purity tellurium (IV) oxide without the usage of liquid oxidants. The process of oxidation of elementary Te was carried out in a flowing quartz glass reactor. Air oxygen was used as an oxidizing agent. The oxidation was conducted at 600-670°C during 24 hours. The produced material was a fine crystalline powder of acicular dendritic crystals of bright white color, identified as β-TeO2 due to X-ray. It was as pure as 5N7 due to ICP-MS. The β-TeO2 crystal grown form the synthesized water-free preparation has demonstrated better optical properties towards the crystals grown from commercial TeO2, produced by the «wet» technology.

The theoretical and experimental analysis of the ternary system Zn-Se-Fe for obtaining new fundamental information on phase using X-ray analysis and inductively coupled plasma mass-spectrometry is carried out. New experimental data of isothermal annealing in the Zn-Se-Fe system at the temperatures 730, 814, 1073 K by X-ray studies confirms the reliability of theoretical isothermal sections. The information on Fe solubility and concentrations of native point defects of atomic scale at bi- and monovariant conditions at 1073 and 1273 K have been carried out. Taking into account the new data on phase equilibria, it is possible to fabricate active ZnSe:Fe2+ elements to create an effective laser operating at the temperature of 300 K with 1.52 Joule emission energy with efficiency of ≈50% relative to the absorbed energy.