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The bulk of the LiNa5Mo9O30 (LNM) crystals were successfully grown in the [010] and [001] directions without internal inclusions and cracks, using the Czochralski method with a low temperature gradient. The crystal grown in the [010] direction showed a tendency to twinning. The crystal grown in the [001] direction demonstrated high structural perfection (FWHM = 13″) for the (001) plane and high optical quality Δn ≈ 2 × 10−5. The laser-induced damage threshold was measured along a, b and c axes and was 12.2, 27.0 and 27.5 J/cm2, respectively. The thermo-optical coefficient dn/dT was measured for the main crystallographic axes, which was −5.75 × 10−6, −20.2 × 10−6 and 3.65 × 10−6 K−1 along the a, b and c axes, respectively. The second harmonic generation (SHG) was conducted in the crystalline LNM sample. The maximum efficiency value of 3.5% at a pump power of 12 W was achieved. [ABSTRACT FROM AUTHOR]

The problem of intensification of the melt crystal growth process has been analyzed using CdTe as an actual material. Numerical simulation of 100 mm diameter CdTe crystal growth using the VGF technique has been carried out. The heat–mass transfer was controlled by introducing low-frequency oscillating baffle into the melt, which is a so-called axial vibrational control (AVC) technique. The baffle configuration has been optimized to destroy solid "tails", which were formed near the crucible walls at high cooling rates due to the low thermoconductivity and the corresponding latent heat. Analysis of CdTe homogeneity range showed that during fast crystal cooling, Te micro precipitations were formed, resulting from the decay of oversaturated Cd-rich nonstoichiometric solid solution during the Bridgman crystal growth technique. After full crystallization, a VGF-grown CdTe crystal stays inside the phase field of the high-temperature wurtzite polymorph. This makes it possible to go through the polymorph transition without Te micro-precipitating using the advantages of the VGF-specific feature of very slow cooling. [ABSTRACT FROM AUTHOR]

New oxychloride lead borate glasses in the xPbCl2–(50-0.5x)PbO–(50-0.5x)B2O3 system were synthesized with a maximum lead chloride content of 40 mol%. The characteristic temperatures and mechanical and optical properties were studied. The incorporation of lead chloride led to a significant expansion of the transparency range in the UV (up to 355 nm) and IR regions (up to 4710 nm). Decreases in the Vickers hardness, density, and glass transition temperature were the consequences of a change in the structure. The studied glasses are promising materials for photonics and IR optics. The structure of the PbCl2–PbO–B2O3 system was analyzed in detail using vibrational spectroscopy and X-ray diffraction. [ABSTRACT FROM AUTHOR]

Bismuth-germanate glasses, which are well known as a promising active medium for broadband near-infrared spectral range fiber lasers and as an initial matrix for nonlinear optical glass ceramics, have been synthesized in a 5–50 mol% Bi2O3 wide concentration range. Their structural and physical characteristics were studied by Raman and FT-IR spectroscopy, differential scanning calorimetry, X-ray diffraction, optical, and luminescence methods. It has been found that the main structural units of glasses are [BiO6] and [GeO4]. The growth in bismuth oxide content resulted in an increase in density and refractive index. The spectral and luminescent properties of glasses strongly depended on the amount of bismuth active centers. The maximum intensity of IR luminescence has been achieved for the 5Bi2O3-95GeO2 sample. The heat treatment of glasses resulted in the formation of several crystalline phases, the structure and amount of which depended on the initial glass composition. The main phases were non-linear Bi2GeO5 and scintillating Bi4Ge3O12. Comparing with the previous papers dealing with bismuth and germanium oxide-based glasses, we enlarge the range of Bi2O3 concentration up to 50 mol% and decrease the synthesis temperature from 1300 to 1100 °C. [ABSTRACT FROM AUTHOR]

Freeze-drying is often used as a final stage to produce three-dimensional porous matrices for medicine. Because a pure solvent crystallizes first during freezing, it acts as a pore-forming agent. The size of the solvent crystals primarily depends on the cooling rate and the composition of the material to be frozen. Ultrasonic treatment also affects the size of crystals and can be used to control the structure of a porous matrix. This article describes the effect of ultrasound (40 kHz, 50 W) applied at the preliminary freezing stage of polysaccharide solutions (alginate, chitosan, alginate–chitosan and alginate–gelatin) on the finished matrix properties. The most attention was paid to the effect of ultrasound on the size and shape of crystals formed during freezing, which leads to a change in the porous structure of the matrices after solvent sublimation. As a result of changes in the microstructure, a number of differences in the vibrational spectra of the molecules and the values of pore volume, sorption capacity, permeability and degradation of matrices were identified. Such changes in the structure of materials, as well as the emerging directionality of pores, together can affect the process of cell cultivation in these polysaccharide matrices, which can be useful in solving problems of tissue engineering. [ABSTRACT FROM AUTHOR]

Special techniques for deep purification of ZnO and WO3 have been developed in this work. A ZnWO4 single crystal has been grown by the Czochralski method using purified ZnO and WO3 chemicals, along with the ZnWO4 crystal-etalon, which has been grown at the same conditions using commercially available 5N ZnO and WO3 chemicals. The actual accidental impurities compositions of both the initial chemicals and the grown crystals have been measured by inductively coupled plasma mass-spectrometry. A complex of comparative spectroscopic studies of the crystals has been performed, including optical absorption spectra, photo-, X-ray-, and cathodoluminescence spectra and decay kinetics, as well as the photoluminescence excitation spectra. The revealed differences in the measured properties of the crystals have been analyzed in terms of influence of the accidental impurities on these properties. [ABSTRACT FROM AUTHOR]

In the present research, an individual Bi2GeO5 crystalline phase is successfully synthesized on air from Bi2O3‐Bi‐GeO2 batch in which some part of bismuth oxide is replaced by metallic bismuth to create an oxygen deficiency. The crystallization process is carried out by three methods: heterophase synthesis, melt cooling, and glass crystallization. The structure of the formed crystalline phases as well as the influence of the bismuth metal quantity and synthesis temperature on crystallization results have been investigated by X‐ray diffraction (XRD). It is found that both the melt temperature rising, and an increase of metallic bismuth amount led to the formation of an individual Bi2GeO5 phase. The optimal initial batch compositions and crystallization conditions to produce an individual Bi2GeO5 or Bi4Ge3O12 phase have also been found. [ABSTRACT FROM AUTHOR]

The method of synthesis of a monophase boron phosphate (BPO4) powder has been refined. Single crystals of BPO4 free from solvent inclusions and cracks have been obtained by the top‐seeded solution growth technique with the seed orientation [010]. The growth is carried out under conditions of a low axial temperature gradient in the melt‐solution, which is varied in the range of 1–4°C cm−1. The value of the temperature gradient that promotes the growth of defective crystals is determined. The absorption spectra and optical homogeneity of crystals are studied. The chemical composition of polycrystalline BPO4 is studied using inductively coupled plasma mass spectrometry. The purity of the synthesized powder is better than 4 N. [ABSTRACT FROM AUTHOR]