The review primarily considers the scientific progress in the identification of impurities, molecular compounds, and heterophase inclusions in high-purity sulfur. Methods for their determination, established by the present time, based on atomic emission spectrometry, mass spectrometry, colorimetry, gravimetry, titrimetry, turbidimetry, conductometry, gas chromatography, infrared spectrometry, chromatography–mass spectrometry, and laser ultramicroscopy are thoroughly characterized.

Цель работы – анализ уровня макро- и микроэлементов в отдельных зонах опухоли при различных степенях анаплазии глиальных опухолей. Материалы и методы. Определены особенности элементного статуса отделов глиальных опухолей при различных степенях анаплазии. Для анализа использован метод атомно-эмиссионной спектрометрии с индуктивно связанной плазмой. Результаты. Проведенный анализ свидетельствует о повышенной кумуляции макро- и микроэлементов в ткани глиом по сравнению с тканью головного мозга практически здоровых людей. Показано, что концентрация меди, железа, цинка в перитуморальной зоне глиом при высоких степенях анаплазии (при метастазировании) выше, чем при Grade I, II, а уровень микроэлементов, способных активировать апоптоз клеток и/или ингибировать сигнальные пути, регулирующие пролиферацию и ангиогенез при глиальных опухолях (литий, селен) в пертуморальной зоне, при высоких степенях анаплазии – ниже. Заключение. Выявление групп микроэлементов, меняющих уровень в перитуморальной зоне глиом при метастазировании, может быть использовано для дифференциальной диагностики степени анаплазии этих опухолей, а также лечь в основу терапии злокачественных новообразований головного мозга.

A procedure is developed for the high-precision determination of matrix elements of high-purity glasses of the Ga–Ge–Te–I system, containing from 5 to 15 at % Ga, from 10 to 20 at % Ge, from 69 to 75 at % Te, and from 1 to 6 at % I, using inductively coupled plasma atomic emission spectrometry. The procedure includes two stages independent of each other: determination of the ratio of the mass fractions of Ga and Te to the mass fraction of Ge (stage 1) and determination of the mass fraction of I (stage 2) in the glass sample. Based on these values, the mass and mole fractions of each matrix element of the analyzed sample were calculated. Sample preparation includes the acid dissolution (provides quantitative transfer of Ga, Ge, and Te into the solution) and alkaline opening (provides quantitative transfer of I into the solution) of samples. The accuracy of the results of analysis was confirmed by comparing the results of an analysis of model solutions and model glass samples with the calculated composition. The estimated uncertainty of the results of analysis is 0.05–0.1 at % at P = 0.95.

The study is aimed to develop a method for preparing especially pure GexTe100_x glasses that provides low oxygen impurity content and, at the same time, high accuracy of a given, desired composition. It is shown that the conventional distillation of the Ge20Te80 melt can lead to a deviation in the glass composition from 0.5 to 2.1 at.% depending on the number of stages due to the thermal decomposition of GeTe. Such deviations in the composition have a significant effect on the crystallization of glasses upon heating and the values of the characteristic temperatures. A method for purification of GexTe100_x charge that makes it possible to minimize the deviation of the glass composition from the desired value is developed. The method is based on creating a constant tellurium vapor excess over germanium(II) telluride that suppresses its thermal decomposition. This is achieved by separate condensation of tellurium and GeTe and their subsequent successive evaporation. Two options for practical implementation of the method with the same efficiency, differing in the initial stage of the charge synthesis, are proposed. Using the developed method, Ge20Te80 glass samples with an oxygen impurity content of <10 ppb(wt) and a composition deviation of & LE;0.2 at.% are prepared.

The ability of rare-earth elements (REEs) to bind oxygen impurities in Ge20Te80 and Ga10Ge15Te75 telluride glasses is studied. Thermodynamic calculations and experiments show that REEs in glasses, with the exception of Eu, can significantly reduce the content of oxygen impurities chemically bound with germanium, tellurium, and gallium. The most promising oxygen getters are established to be Y, Gd, Lu, Tm, Dy, Tb, and Ho. The advantages of REEs as the getter compared to traditionally used aluminum are: more complete removal of the getter residue during the distillation of tellurium melt and chalcogenide glass; the absence of intense absorption oxide bands in the range of glass transparency; lower etching ability in relation to the silica-glass reactor.

A method for preparing high purity rare earth elements (REEs) doped chalcogenide glasses, in which all com-ponents of the charge (Ge, Sb, Ga, Se) and REEs are loaded and subjected to additional purification by combining reactive distillation of germanium and antimony selenides and chemical vapor transport (CVT) of gallium and REE iodides under high vacuum conditions, is proposed. The technique is tested in the preparation of Ga5Ge20Sb10Se65 glass doped with (1-20)center dot 10(19) at center dot cm(-3) Ce, Pr, Nd, Tb, Dy. In the best glass samples, the content of impurities was as following: metals - 0.03-4 ppm(wt), hydrogen - 0.01 ppm(wt), heterogeneous micron sized inclusions < 102 cm(-3). The novel high purity level of Ce3+ and Tb3+ doped glasses made it possible to achieve reproducible practically significant characteristics of laser generation power in the 4.5-5.9 mu m range in bulk samples and optical fibers in pulsed and continuous modes at room temperature.

Расширены сведения о молекулярной форме примесей углерода, водорода и кислорода в особо чистом селене. Методом хромато-масс-спектрометрии в селене впервые установлено присутствие и содержание примесей углеводородов, их галогенпроизводных, серо- и селенсодержащих веществ. Методом атомно-эмиссионной спектроскопии с индуктивно-связанной плазмой определено содержание примесей 46 элементов в селене. Данные о молекулярной форме примесей углерода, кислорода и водорода в коммерческом особо чистом селене облегчат выбор и оптимизацию методов его дальнейшей глубокой очистки.

— This paper presents additional data on carbon, hydrogen, and oxygen impurities in molecular form in extrapure selenium. Using gas chromatography/mass spectrometry analysis, selenium has been shown for the first time to contain hydrocarbons, halogenated hydrocarbons, and sulfur- and selenium-containing substances. Forty-six elemental impurities were detected in selenium by inductively coupled plasma atomic emission spectroscopy. Data on carbon-, oxygen-, and hydrogen-containing molecular impurities in commercially available extrapure selenium will be helpful in choosing and optimizing methods for its further ultrapurification.

The purpose of this work is to study phase formation during quenching of glass-forming melts and crystallization of GaxGe40-xS60 glasses (x = 0-15 at.%), which are promising materials for optical IR glass-ceramics. The stability against crystallization of the glasses is determined to decrease with increasing gallium content. In the case of the glass-forming melts, the stability against crystallization increases in the range x = 0-8 at.% and then decreases. It is established that, during crystallization, not pure phases of binary sulfides are formed, but their solid solutions. When quenching the melts with a gallium content of 10-15 at.%, Ga2-xGexS3 solid solutions, which are isostructural to one of the polymorphic modifications of gallium sesquisulfide, are crystallized. Solid solutions form skeletal crystals, the growth of which leads to the formation of a dendritic crystal structure. Micro-liquation in the GaxGe40-xS60 glasses is observed.

A technique for preparation of high-purity Ga-Ge-S and Ga-Sb-S glasses is developed. The method includes two main stages: synthesis of gallium(III) sulfide by interaction of gallium(III) iodide with sulfur in an evacuated silica-glass reactor; synthesis and loading of germanium(II) sulfide and antimony(III) sulfide in the reactor. Thermodynamic modeling of Ge-S and Sb-S systems is carried out. Optimum conditions for the synthesis of germanium and antimony sulfides as components of the chalcogenide charge are theoretically and experimentally determined. High-purity Ga5Ge35S60 and Ga8Sb32S60 glasses with the 0.2-0.6 ppm(at) hydrogen impurity content in the form of SH-groups and heterogeneous micron and submicron-sized impurity inclusions of less than 10(2 )pieces/cm(3) are prepared.

The isotope effect of germanium (Ge-M, M = 72, 74, 76) in the crystallization kinetics of the especially pure glass-forming system (GeS1.35)-Ge-M-S-32 from the state of supercooled melt has been revealed and quantitatively characterized by differential scanning calorimetry (DSC) in the range 320-900 K. The data obtained in the nonisothermal regime on the increase in the crystallization temperatures of GeS (from 417.2 degrees C to 422.2 degrees C) and GeS2 (from 489.5 degrees C to 491.6 degrees C) in the series of these compounds with Ge-72, Ge-74, Ge-76 isotopes were supplemented by the necessary description of the kinetic isotope effect according to the ratio of the rate constants of quasi-chemical crystallization reactions. The found parameters can be used to plot the temperature-time dependences of the crystallization degree alpha (t, T), reflecting in the form of parameters the kinetic isotope effect in the glass under study.

Elemental and heterophase impurities in some rare-earth elements (Ce, Pr, Nd, Tb, and Dy) and features of their influence on optical and emission properties of doped chalcogenide glasses are determined. The main impurity elements in REEs are: W, Mo, Fe, Mg, Ti and some other metals (up to 8400 ppmw), fluorine and oxygen in the form of oxofluorides and oxides (up to 680 ppmw), and hydrogen in dissolved form (up to 68 ppmw). In doped Ge20Sb10Ga5Se65 glasses, the REEs are the main source of impurities of d-transition metals, non-metals (Si, F), gas-forming impurities (H, O), and inclusions. Heterogeneous inclusions, the source of which is REEs, make the greatest contribution to optical losses in doped chalcogenide glasses. Impurities of hydrogen in the form of SeH groups, oxygen in the form of dissolved oxides, d-transition metal ions, and REE analogues affect the rate of non -radiative relaxation of the excited state of REE.

The wettability of stainless steel grades AISI 201, AISI 304, AISI 316Ti and AISI 430 with a Ge28Sb12Se60 glass melt was obtained in the temperature range 480-520 degrees C. The adhesive strength of the glass-to-metal boundary formed during cooling of the melt was studied in the temperature range of contact formation (330-450 degrees C). The wetting edge angles decrease linearly with increasing temperature. An increase in the temperature of the adhesive contact formation leads to an exponential increase in the adhesive strength. The highest adhesion is observed when using AISI 201 steel as a substrate, the lowest when using AISI 430 steel.

The IR spectrometric method for determination of hydrogen impurities in the form of SH-groups in liquid sulfur is developed. The temperature dependence of the content of SH-groups in sulfur samples in the range of 300-550 degrees C is studied. The technique for deep sulfur purification including vacuum distillation, passing sulfur vapor through catalysts based on silicon, aluminum and cerium oxides, and filtering the vapor using high-purity silica-glass micro-filters is developed. The sulfur containing 40 +/- 4 ppb(at) SH-group is prepared. By using the high-purity sulfur samples of various origins, Ga5Ge36 S-59 glasses are synthesized. Sulfur is shown to be the essential source of hydrogen impurity and heterogeneous inclusions in the glasses. The minimum hydrogen content in the form of SH-groups in the Ga5Ge36S59 glass sample, prepared from the sulfur purified using the developed technique, is 0.10 +/- 0.02 ppm(at). The content of heterogeneous micron-sized inclusions in this glass sample is not exceed 10 pieces/cm(3).

We developed a procedure for the high-precision determination of matrix elements of glasses of the Ga–Ge–As–Se system, including those doped with praseodymium, in the range of concentrations of gallium from 1 to 5 at %, germanium from 16 to 24 at %, arsenic from 14 to 18 at %, and selenium from 57 to 65 at %. A procedure for determining 0.05–0.5 wt % of praseodymium in these glasses by inductively coupled plasma–atomic emission spectrometry is also proposed. The expanded uncertainty (P = 0.95) of the results in determining the matrix elements ranged from 0.05 to 0.1 at %, and for praseodymium, it was from 0.002 from 0.02 wt %. A method for preparing standard solutions necessary to achieve the stated level of uncertainty of the analysis results is described. The minimum sample weight for determining matrix elements is approximately 1 mg, and for the determination of praseodymium, it is approximately 10 mg, which enables analyzing not only bulk glass samples but also fibers made of them.

The elemental composition of Ge-Se glasses prepared by different methods and the distribution of Ge and Se along the bulk sample length are investigated by inductively coupled plasma atomic emission spectrometry. The estimated uncertainty of Ge and Se content measurement is 0.02-0.05 at.% (P = 0.95). To date, these results are the most accurate for determining the elemental composition of optical Ge-based chalcogenides. The minimum required mass of the analyzed glass samples does not exceed 1 mg. Partial phase separation in the Ge-Se system leads to a significant (+2 at.%) deviation of the chemical composition of Ge-Se glasses along the length of the bulk sample from the specified value. This is the first time that the elemental composition of single-index Ge-Se fibers along the fiber length has been studied. The rod drawing method allows the fabrication of optical fibers with composition deviation along the length of 0.03-0.05 at.%. In the case of drawing by the crucible method, the deviations of the fiber composition can reach 0.16 at.% compared with the initial glass sample.

One of the most important stages of the high-purity chalcogenide glasses’ analytical control is the determination of matrix elements’ content with the uncertainty at the levels of 0.1–0.2 mol.%. The content of the macro-components may differ from the composition of the initial charge; therefore, an important task is the macro-composition determination of the final materials. This article describes the development of the technique for determining the matrix elements of high-purity Ge-Se-Te glasses in the range of germanium content from 10 to 35 mol. %, selenium and tellurium content from 20 to 50 mol. % with the expanded uncertainty within 0.01–0.2 mol. % (P = 0.95) using the inductively coupled plasma atomic emission spectrometry (ICP-AES). A simple technique for the preparation of primary calibration solutions from pure elementary Ge, Se and Te is proposed. The correctness of the analysis results is confirmed by comparing the calculated matrix composition of model glass samples, prepared by direct synthesis from high-purity simple substances in the sealed quartz glass ampoule, with the analysis results. The main advantage of the proposed analysis technique is the absence of the need for the reference samples identical to the analyzed material, which is especially important for determination of new materials’ matrix composition. The minimum sample mass for the determination of matrix elements is about 1 mg, which makes it possible to analyze not only bulk glass samples, but also fibers and expensive materials.

The adhesive strength of chalcogenide GexSe100-x(15 <= x <= 26) glasses to silica glass is studied by the method of normal detachment depending on germanium content, temperature of contact formation and detachment temperature. The value of adhesive strength increases exponentially as the detachment temperature increases passing through the maximum near the glass transition temperature of adhesive. The increase in the temperature of contact formation between chalcogenide and silica glasses in the range of 260-370 degrees C leads to linear increase in adhesion strength. The Ge20Se80 glass is established to show the maximum adhesion (2.6 +/- 0.3 MPa) to silica glass among the studied compositions at the temperature of formation of adhesion contact above 320 degrees C.

The method for preparation of high-purity Ge-Se glasses with the low content of hydrogen and oxygen impurities is developed. The method includes following stages: selenium purification by chemical-distillation technique; passing selenium vapors over a mixture of Ge batch and 2 wt% of Al for loading the components into the reactor; glass melting, quenching and cooling. Optical losses in the unclad fiber did not exceed 1 dB/m in the spectral ranges 2.0-4.3 mu m and 4.8-7.8 mu m; the minimum optical losses were 0.77 dB/m at 5.6 mu m. The fiber is characterized by the record low content of oxygen, chemically bound to germanium, which is 0.013 +/- 0.002 ppm(wt), the concentration of hydrogen in the form of Se-H groups is 1.77 +/- 0.12 ppm(at). The silica reactor is shown to be the source of impurities of hydrogen, metals and heterogeneous particles in Ge-Se glasses.