Tellurium Impurity Research Articles

A technique for depositing iron, tungsten, molybdenum, and chrome in the determination of selenium and tellurium in alloy steel by ICP-AES method

Direct determination of the content of selenium and tellurium impurities in metallurgical materials by the method of inductively coupled plasma atomic emission spectroscopy (ICP-AES) is difficult due to spectral and non-spectral interference from macrocomponents present in the materials under study. The separation of micro-(Se, Te) and macro-components (Fe, W, Mo, Cr, Cu, Ni, Co) through preliminary precipitation is the goal of the study. The use of barium acetate and sodium fluoride as precipitants are shown to provide an effective separation of Se and Te from Fe, W, Mo, and Cr (the content in the analyzed solution is less than 0.1 wt.% of the original) and partial separation from Cu, Ni, and Co (the content in the analyzed solution from 25 to 55 wt.% of the original). Optimal conditions for the deposition of macrocomponents (Fe, W, Mo, Cr) and inhibition of the process of coprecipitation of selenium and tellurium on sediments of macrocomponents for their subsequent ICP-AES determination were determined. The optimal pH for the precipitation of macrocomponents equals 1. The optimal mass of precipitants (barium acetate and sodium fluoride) is 10 and 3 g, respectively. To inhibit the process of coprecipitation of selenium and tellurium on sediments of macrocomponents, it is proposed to use hydrofluoric acid. The optimal volume of hydrofluoric and hydrochloric acids for inhibiting the process of coprecipitation of analytes on sediments of macrocomponents was determined (3 and 6 cm3, respectively). The developed procedure for separating micro-Se, Te from macro-components was tested on standard samples of alloyed steels using the «spike» method. The technique is characterized by satisfactory accuracy and reproducibility, the limit of determination of analytes after separation of macrocomponents is 10–3 wt.%.

Tunable magnetic and optical properties of transition metal dihalides by cation alloying

Alloying has been a tradition in materials science that has enabled groundbreaking discoveries in semiconductor technologies, optics, and photovoltaics, among others. While alloying in traditional systems is relatively well established, the effects of alloying in the emerging van der Waals (vdW) two-dimensional (2D) magnets are still in their infancy. Using ${\mathrm{Co}}_{1\ensuremath{-}x}{\mathrm{Ni}}_{x}{\mathrm{Cl}}_{2}$ as a testbed system, our results show that chemical vapor transport of stoichiometric mixtures of $\mathrm{Te}{\mathrm{Cl}}_{4}$, Co, and Ni enables the synthesis of highly crystalline vdW magnetic alloys with excellent control over the Ni concentration ($x$) without any tellurium impurities or phase separation. The method is advantageous compared to binary $\mathrm{Co}{\mathrm{Cl}}_{2}$ and $\mathrm{Ni}{\mathrm{Cl}}_{2}$ precursor mixtures which only produce small-sized crystals with a large compositional variation. Magnetic measurements show that the degree of magnetic anisotropy, Weiss temperature, and N\'eel temperature (${T}_{\mathrm{N}}$) strongly correlate to the Ni concentration, offering a tune-knob to engineer the magnetic behavior of transition metal dihalides. First-principles calculations offer further insights into how the increasing Ni content influences the interlayer and intralayer magnetic couplings and the resulting magnetic response. Overall, our findings provide an important avenue toward metal cation alloying in dihalide 2D vdW magnets and offer means to tune their magnetic behavior on demand.

Экструдированный материал на основе Bi0.85Sb0.15 для термоэлектрических преобразователей

In order to create a sufficiently strong material with thermo- and magneto-thermoelectric figure of merit close to single-crystal samples of material based on Bi-Sb systems, extruded samples of Bi0.85Sb0.15 solid solution were obtained and the effect of composition, heat treatment mode, grain size and tellurium impurities was investigated on their thermoelectric properties in the temperature range ~ 77-300 K and magnetic field strength H up to ~ 74∙104A/m. We managed to obtain extruded material with thermo- and magneto-thermoelectric figure of merit ~6.2∙10-3 K-1 and ~7.2∙10-3K-1 at ~ 77 K, respectively, with strengths ~ 3 times higher than the strength of single-crystal samples of this composition, which are suitable for use in low-temperature thermoelectric converters.

Electrical and Galvanomagnetic Properties of Extruded Samples of Bi85Sb15 Solid Solutions with Pb and Te Impurities

The effect of tellurium impurities on the electrical conductivity (σ), Seebeck coefficient (α), and Hall coefficient R of extruded Bi85Sb15 + 0.001 аt.% Pb is studied in the temperature range 77–300 K. It is found that doping with tellurium impurities up to 0.001 at. % compensating acceptor Pb atoms leads to a strong decrease in the electron density and, consequently, to an increase in σ and significant decrease in the values of α and R. The materials obtained can be used as the n-branch of thermoelements operating at temperatures of ~77 K.

К истории минералогических исследований в Забайкалье

The Olimpiada gold-sulfide deposit in the Yenisei Ridge, as per the results of additional exploration of the recent years, has confirmed its uniqueness in terms of reserves (1560 t) and ore extent in the depth (1500 m). Meanwhile, no indicators of thinning out and change in mineralization parameters have been noted. Oxidized ores mined out to date were developed in the upper part of the deposit. About 200 t of metal have been mined from them. The deposit is confined to the silicate and carbonate band of the Lower Riphean Kordinskaya suite clastic stratum. Granitoids separated from the deposit at 1.5 km and above surround the deposit. Introduction of intrusions in the Tatar-Ishimbinskaya tectonic zone assisted in the formation of compensation synformal depressions (Innokentyevskaya and Chirimbinskaya synclines) in the contact zones of intrusions united by the antiformal rock unit (Medvezhinskaya anticline). These connected W-shaped structural elements represent the structure of the ore field. Subhorizontal shifts in the area shaped the magmatogene structure into tectonic syncline and anticline folds. The ore bodies are concentrated in fold curves and rock bends at limbs. The northeastern curve of the Medvezhinskaya anticline has the highest ore content. There, the deposits of the northern and southeastern limbs of the Medvezhinskaya antiform are connected and represent a single ore body sloping to the southeast. No indicators of thinning out at the depth have been revealed. The micaceous-quartz-carbonate matrix of the sulfide-disseminated ores has been boudinaged, milonite-altered and folded into minor folds up to plication. The main ore forming elements, including Au, Ag, Fe and Sb, form dissemination of native minerals, sulfides, sulfosalts and tellurides. In terms of the mineralogical and geochemical composition the ores are divided into gold-arsenic and gold-arsenic-antimony ores separated spatially. The gold-arsenic-antimony ores with the geochemical mercury and tellurium impurity are confined to the northeastern deposit of the ore body. Metamorphism in the tectonic-metamorphic zone of the deposit occurred at the temperature of 400–420оС and the pressure of 3–4 kbar in chlorite and biotite zones, and in the garnet and margarite zone — at 580-605оС and the pressure of 7.2–7.5 kbar. Metasomatosis of silicate and carbonate rocks with skarnoid formation (Act+CZo+Gar+Sph) occurred at 320–480оС and the pressure of 1.3–1.5 kbar, and of acidic metasomatites (silicified and sericitized rocks) at Т=290–380оС and Р=1.0–3.0 kbar. The polystage hydrothermal quartz-gold-sulfide process of aggregate formation occurred in the interval of 460–110оС. The age of the main stages of ore formation is within 817–660 Ma. The industrial ores of gold-arsenic composition have the age of 758–803 Ma, and the gold-arsenic-antimony ores are 660–795 Ma old. The isotope and geochemical studies testify to the participation of the crust and mantle substance in the deposit formation. Aquatic-chloride-carbon dioxide solutions saturated with hydrocarbons participated in the ore substance transportation.

Effect of chromium and tellurium impurities on the thermoelectric parameters of galena

Concentration dependences of the Seebeck coefficient, resistivity, and thermal conductivity of thermoelectric PbS crystals with chromium (0 < x ≤ 0.01) and tellurium (0 < y ≤ 0.03) impurities are examined in the temperature region of 300–800 K. It is shown that the introduction of chromium increases the number of free electrons in PbCr x S 1–x crystals and reduces the Seebeck coefficient. However, an increase in the concentration of tellurium in PbCr x S 1–x–y Te y alloys raises the Seebeck coefficient while simultaneously reducing the thermal conductivity. As a result, the thermoelectric efficiency of PbCr x S 1–x–y Te y crystals increases. The reasons for the observed effects are discussed.

Investigation of X-ray diffraction limitations upon the analysis of tellurium-atom injection into GaAs epitaxial layers

GaAs lattice “superdilation” caused by an introduced tellurium impurity, which is well known in publications, is experimentally studied. This phenomenon consists in the fact that the GaAs-lattice dilation can be more than 10 times greater than expansion that would appear upon the replacement of arsenic atoms with tellurium atoms if calculations are performed using the current-carrier concentration and Vegard’s law. The given phenomenon has already been observed at n Te > 3 × 1018 cm–3. A series of GaAs epitaxial layers heavily doped with tellurium and grown via metal-organic chemical vapor deposition are investigated using high-resolution X-ray diffractometry (HRXRD), secondary-ion mass spectrometry (SIMS), and the Hall effect. It is demonstrated that, despite a high Te concentration (1020‒1021 cm–3) in the layer and variations in the growth conditions, the concentration estimates based on HRXRD data depend linearly on the results of elemental analysis performed by means of SIMS. The GaAs lattice expands even somewhat slighter as compared to the case where arsenic atoms are replaced with all Te atoms injected into the layer. At the same time, the Hall carrier concentration decreases sharply beginning at 2 × 1020 cm–3. In accordance with the obtained results, the examined phenomenon can be interpreted as the strong compensation of donor and acceptor carriers rather than as superdilation.

Theoretical study of selenium and tellurium impurities in (ZnO)6 clusters using DFT and TDDFT

AbstractZinc oxide (ZnO) nanostructures have attracted much interest due to their potential applications in various fields including optoelectronics, glass industries, and solar cells. These compounds hold the promise of creating new materials that can advance energy technologies. In this work, a series of (ZnO)6 clusters with selenium and tellurium applied as substitutional impurities has been studied. The investigated structures have been produced through the doping of (ZnO)6 clusters by replacing an oxygen atom with a selenium or a tellurium atom at each time. The ground state geometric parameters of (ZnO)6 structures, containing selenium or tellurium atoms as substitutional impurities, were calculated using density functional theory (DFT) with B3LYP and LanL2DZ basis set. Excited state energies and absorption wavelengths were computed using time‐dependent‐DFT (TDDFT). For the calculation of emission wavelengths, Hartree–Fock configuration interaction singles (HF/CIS) has been used in order to perform the excited state geometry optimization. This work led to some important results that can be helpful for developing novel THz sensitive materials and imaging detectors that may be an alternative to x‐rays detectors for radiology as well as for the development of solar cells and electroluminescent diodes. Zinc oxide (ZnO) nanostructures have attracted growing interest due to their potential applications in many technological fields, including optoelectronics, the glass industry, and energy. The presence of impurities, in particular selenium and tellurium, in ZnO‐based clusters can affect their structural and spectroscopic properties. Some of these doped nanostructures have favorable Terahertz emission characteristics that make them good candidates for applications in biology and medicine.

Ultrapurification of tellurium and cadmium by distillation and crystallization

We have developed physicochemical principles of the ultrapurification of crude tellurium and cadmium by distillation and crystallization and determined the effective solid-liquid distribution coefficients of impurities in tellurium and cadmium. Based on the observed behavior of impurities in different ultrapurification processes, we have proposed a combined process for the preparation of high-purity (99.9999%) tellurium and cadmium.

Radiochemical precipitation studies for separation of iodine from tellurium and other trace impurities

Precipitation of radiotellurium, containing trace radioimpurities, has been carried out from sulfate media at different pH-values. The highest precipitation yield was achieved at the region of pH ~4–6. Quantitative uptake by the formed precipitate was noticed for (i) 54Mn, 110mAg and 125Sb over all the pH-range of study (pH 1.7–9.2), (ii) for 65Zn and 60Co in the regions of pH ~6–8 and pH 6–8.8, respectively, and (iii) for 134Cs in the region of pH 1.7–2.8, while its percent uptake fluctuated around 60.5 % in the region of pH 4.4–6.4. Further precipitation studies have been conducted for a mixture of 125I and radiotellurium from sulfate, nitrate and chloride media at pH-values of 6.0 and 7.5. The highest 125I recovery yield in the obtained supernatant was 95.0 ± 1.3 %, which was achieved with sulfate medium at pH 6.0 with percent uptake values of 5.0 ± 1.3, 98.9 ± 0.9 and 62.0 ± 4.6 % of 125I, 123mTe and 134Cs, respectively, and quantitative uptake of 54Mn, 110mAg, 125Sb, 60Co and 65Zn by the precipitated tellurium. Thereafter, the supernatant was further acidified with H2SO4 and boiled, after adding H2O2, for 3 h. >99 % of 125I was distilled off from the acidified supernatant. The distilled of 125I was received in 0.1 M NaOH + 1 % Na2S2O3 solution, with a radionuclidic purity of >99.99 %, radiochemical purity of >99.8 % as I− and pH ~13.

XPS of Impurities Influence on Electronic Structure of Sn2P2S6 Ferroelectrics

Influence of impurities of In, Te and Ge on the core level binding energies and the electronic structure of the valence band of Sn2P2S6 ferroelectric crystals was investigated by X-ray photoelectron spectroscopy together with electron spectra first-principles calculations. It was found that the indium impurity induces donor states, the tellurium impurity modifies energy structure near the top of valence band, and germanium impurity improves stereoactivity of the cation sublattice that is related to the ferroelectric phase transition nature.

An improved hydrometallurgical route for tellurium production

In recent years, tellurium has been extensively used in the manufacture of semiconductor materials. For this type of application, high-purity tellurium is required. Selenium, lead and silicon are usually the main impurities in tellurium. During the electrolytic refining of copper, tellurium gold and silver are collected in the anode slimes. A pyrometallurgical treatment is used to recover gold and silver from the decopperized anode slimes whereas tellurium is oxidized and skimmed off from the refining furnace as a Na2CO3-based slag. In the slag, tellurium is present as sodium tellurite (Na2TeO3), which is further water-leached from the slag. The first step in the conventional process for tellurium recovery consists of the precipitation of the tellurium contained in the leaching solution as tellurium dioxide (TeO2). The solid TeO2 is then dissolved under acidic conditions for its further reduction with sulfur dioxide gas (SO2). In this paper, an alternative route for tellurium production is presented in which a sodium tellurate [Na2TeO4] intermediate is obtained by oxidation of the sodium tellurite in an alkaline solution following the water leaching step. Sodium tellurate is then dissolved in acid media and high-purity tellurium is obtained by reduction with SO2 gas. Experimental tests under laboratory conditions indicate that the novel process yields higher precipitation selectivity for tellurium than the conventional process. A comparison of its efficiency concerning impurities co-precipitation with respect to the conventional process is discussed.

Optical properties of ZnTe layers formed over surface-modified ZnSe substrates

Heterolayers of zinc telluride were created using the isovalent replacement method over the low-resistive mono-crystalline substrates of zinc selenide, doped with the isovalent tellurium impurity. It was found that the surface structure of the heterolayer is being determined by the treatment of the substrate layers and inherits its properties, namely mirror-smooth or matte (modified) surfaces. The latter type corresponds to the quantum-scale surface formations responsible for the wide unstructured spectral band with photon energies significantly exceeding the bandwidth of the materials studied.

Self-assembling of zinc and tellurium impurities in zinc-blende MgS

Conditions providing a thermodynamic advantage governing the self-assembly of Zn and Te impurities in metastable magnesium sulfide (MgS) with zinc-blende structure have been theoretically studied. The formation of tetrahedral 1Te4Zn cells is thermodynamically favorable in ZnxMg1 − x TeyS1 − y (x ≥ 4y) solid solutions enriched in MgS in the region of dilute Te concentrations. At temperatures selected for the growth (230°C) and annealing (500°C), the free energy of a solid solution in which separate Te atoms must be surrounded only by Zn atoms is lower than that of the solution with a random arrangement of these impurities. This phenomenon is due to a thermodynamic advantage of the formation of Mg-S and Zn-Te bonds over Zn-S and Mg-Te bonding, as well as due to a decrease in the elastic strain energy upon self-assembly of the given isoelectronic impurities.

Time-resolved photoluminescence spectroscopy of individual Te impurity centers inZnSe

Tellurium impurity centers in $\mathrm{ZnSe}$ were individually probed with time-resolved photoluminescence (PL) spectroscopy. Resolution-limited peaks with an ultralow spatial density originate in the recombination of excitons deeply bound to isolated nearest-neighbor isoelectronic Te pairs $({\mathrm{Te}}_{2})$. This interpretation is supported by ab initio calculations. The peaks reveal antibunched photon emission and a doublet structure polarized along $[110]$ and $[\overline{1}10]$. The temperature dependence of the time-resolved PL decay exposes the dark excitonic states which indirectly affect the radiative recombination of single fine-structure split excitons.

Study of segregation process of impurities in molten tellurium after one pass of three conjoint zones in zone refining

Zone-melting process provides a great amount of knowledge about parameters governing the process of optimal purification for tellurium, especially the effective segregation coefficients K eff. A series of 13 values of K eff were determined after one pass n = 1 and one molten zone N = 1 at the same conditions of temperature T and interface velocity V. These values are used to extract a mathematical model of the distribution concentration Ψ 3 (x)= C S / C 0 for n = 1 and N = 3 , treated 13 times for 13 impurities. After 3 passes of tellurium molten zone, a decrease of the concentration of the residual impurities concentrations was registered, and a better fitting between experimental points C S / C 0 with the extracted theoretical model was also observed. Besides, the effect of high conductivity of liquid tellurium was studied; leading to a decrease of the driving forces, therefore the ultimate distribution was enhanced. Under our experimental conditions, we propose N = 3 as maximum number of molten zones needed to achieve an ultimate purification of tellurium with good efficiency.

Photoluminescence of n-type CdGeAs2

Samples of n-type CdGeAs2 were produced by intentional doping with indium, selenium, or telluriumimpurities. A near-edge photoluminescence (PL) band from heavily In-dopedCdGeAs2 samples shifts to higher energy and becomes broader with increasing electronconcentration. The observed shifts in peak energies are compared to predictions fordonor–acceptor pair and free-to-bound (electron–acceptor) recombinations including bandfilling, band tailing, and band gap shrinkage effects due to the high doping levels. Forn>2 × 1018 cm−3, the free-to-bound PL transition related to a shallow 120 meV acceptor level isdominant. A lower energy PL band due to deep acceptors and normally seenfor p-type samples is the only emission observed from less n-type samples(n∼1016–1017 cm−3) doped with indium, selenium, or tellurium impurities. Transitions involvingthe deep acceptor level are not present in the PL for heavily In-dopedCdGeAs2 crystals, which suggests that the deep acceptor may be a Cd vacancy.

The extrinsic photoconductivity of chalcogens in Ge1−x Six solid solutions

The effect of ∼3% of silicon additive on the energy spectra of selenium and tellurium impurities in germanium is studied. The photoconductivity spectra are measured at 80 K in a spectral range from 2.5 to 5 μm. Narrow lines corresponding to the excited states of chalcogen ions are observed against the background of the extrinsic-photoconductivity band. It is found that the spectrum of excited states is not affected by silicon at the concentration used. An increase in the energy gaps between the conduction band and impurity states of the chalcogens is detected.

Measurement of growth rate by thermal pulse technique and growth of homogeneous In xGa 1−xSb bulk crystals

In x Ga 1− x Sb bulk crystal was grown on a GaSb seed under a constant temperature gradient using a GaSb(seed)/InSb/GaSb(feed) sandwich sample. A GaSb feed was dissolved into the InGaSb solution to supply GaSb component during the growth. The temperature gradient in the solution was estimated from the indium composition profile in the grown crystal using the InSb–GaSb pseudo-binary phase diagram. In order to measure the growth rate, tellurium impurity striations were intentionally introduced into the crystal by thermal-pulse technique. The growth rate gradually increased to the constant value and then rapidly decreased. The change of growth rate was reflected in the indium composition profile. Homogeneous In 0.03Ga 0.97Sb was grown by cooling the sample at the optimized value estimated from the temperature gradient and the growth rate.

A New Theoretical Formulation of Temperature Effect on Impurities Diffusion Coefficients in Molten Tellurium

The evolution of effective diffusion coefficients Deff of 13 different impurities in molten tellurium versus temperature T was studied. A new hyperbolic expression Deff = f(T) for these impurities was established for effective segregation coefficients Keff << 1 and for temperatures within the range 730 K–925 K. Experimental values of Keff determined by zone melting process were used to calculate a series of 4 effective diffusion coefficients Deff, at four different temperatures, for each impurity. These experimental results of Deff were fitted with the new expression of Deff = f(T) to confirm its validity. The diffusion mechanism of 13 impurities at the solid–liquid interface was then investigated under our previous experimental conditions (velocity v of interface, the starting concentration C0, and number n of passes). These investigations confirmed that the temperature increase of tellurium molten zone was not convenient to reach an optimal purification by zone melting process.