Tellurium Content Research Articles

Electrical and optical properties of bismuth sulphotelluride [Bi 2(S 1− xTe x) 3] thin films prepared by arrested precipitation technique (APT)

Semiconducting bismuth sulphotelluride [Bi 2(S 1− x Te x ) 3] thin films were grown by using initial ingredients bismuth triethanolamine complex, thioacetamide and sodium tellurosulphite in an aqueous alkaline medium. Thin, uniform, tightly adherent and densely packed deposits are obtained by employing arrested precipitation technique (APT). The optical absorption studies revealed that the films have high absorption coefficient with a band to band (direct) type transitions and the energy gap decreased typically from 1.62 eV for pure Bi 2S 3 down to 0.65 eV for pure Bi 2Te 3. The transition of the material is found to be band to band direct type. The electrical conductivity measurements showed increase in the conductivity with increased tellurium content ( x) in the film. From TEP measurements the films showed n-type of conduction mechanism for all the samples. The thermo power is of the order of μV/K.

Simultaneous determination of bismuth and tellurium in steels by high power nitrogen microwave induced plasma atomic emission spectrometry coupled with the hydride generation technique.

An annular-shaped, high power nitrogen microwave induced plasma (N(2)-MIP) produced at atmospheric pressure by an Okamoto cavity, as a new excitation source for atomic emission spectrometry (AES), has been used for the simultaneous determination of bismuth and tellurium in steels with the hydride generation method. Under the optimized experimental conditions, the best attainable detection limits at the Bi I 195.389 nm and Te I 200.200 nm lines were 110 and 86 ng/ml for bismuth and tellurium, respectively. The linear dynamic ranges for bismuth and tellurium were 300 to 30,000 ng/ml. The presence of several diverse elements was found to cause a more or less depressing interference with the proposed technique. When bismuth and tellurium in steels were determined, a large amount of Fe(III) in the solution caused a severe depressing interference, while the presence of Fe(II) showed little or no significant interference. Of the several interference-releasing agents examined, l-ascorbic acid was found to be the most preferable to reduce Fe(III) to Fe(II) prior to hydride generation. The concentrations of bismuth and tellurium in steels were determined by the proposed technique. The results obtained by this method were in good agreement with their certified values.

Simultaneous speciation of inorganic selenium and tellurium by inductively coupled plasma mass spectrometry following selective solid-phase extraction separation

A new method was developed for the simultaneous determination of inorganic tellurium and selenium species in waters by inductively coupled plasma mass spectrometry (ICP-MS) following selective solid-phase extraction (SPE) separation. Under acidic conditions, only selenium(IV) and tellurium(IV) formed complexes with ammonium pyrrolidine dithiocarbamate (APDC), and the complexes were completely retained on a non-polar C18 cartridge. Te(VI) and Se(VI) passed through the cartridge and remained as free species in the solution, thereafter being determined by ICP-MS. Se(IV) and Te(IV) concentrations were obtained as the respective differences between total selenium and Se(VI), and total tellurium and Te(VI) concentrations. The detection limits (3σ) are 7 ng L−1 selenium and 3 ng L−1 tellurium. Factors affecting the separation and detection were investigated. Coexisting ions did not show significant interferences. This method has been successfully applied to the inorganic selenium and tellurium speciation analysis of water samples with spiked recoveries of 82.3–106%.

Bioreduction of tellurite to elemental tellurium by Pseudomonas mendocina MCM B-180 and its practical application

A microbiological process using Pseudomonas mendocina MCM B-180 was developed for the removal of tellurite from solutions. During the process tellurite was transformed into metallic tellurium. The process, when carried out in a 2-l continuously stirred tank reactor in the presence of sucrose and diammonium hydrogen phosphate as nutrients, removed 10 mg/l tellurium in 12 h with an efficiency exceeding 99.8%. The process could sustain wide variations in pH (5.5–8.5), temperatures (25–45 °C) and initial tellurium concentration (10–100 mg/l). An integrated biosorption–bioreduction process for the treatment of waste photovoltaic modules demonstrates the utility of microbial tellurite reduction.

Speciation analysis of tellurium by solid-phase extraction in the presence of ammonium pyrrolidine dithiocarbamate and inductively coupled plasma mass spectrometry.

Under acidic conditions tellurium(IV) formed a complex with ammonium pyrrolidine dithiocarbamate (APDC). The tellurium(IV) complex was completely retained on a non-polar Isolute silica-based octadecyl (C(18)) sorbent-containing solid-phase extraction (SPE) cartridge, while the uncomplexed Te(VI) passed through the cartridge and remained as a free species in the solution. Only partial Te(IV) was retained on the SPE cartridge for samples without addition of APDC. On the basis of different retention behaviours of the complexed Te(IV) and uncomplexed Te(VI), a simple and highly sensitive method is proposed for the determination of total tellurium and Te(VI) by SPE separation and inductively coupled plasma mass spectrometry (ICP-MS) detection. The Te(IV) concentration was calculated as the difference between total tellurium and Te(VI) concentrations. The detection limit (3 sigma) is 3 ng L(-1) tellurium. Factors affecting the separation and detection of tellurium species were investigated. Coexisting ions did not show significant interferences with the Te(IV)-APDC complex retention and the subsequent ICP-MS detection of Te. The method has been successfully applied to the tellurium speciation analysis in waters with spiked recoveries for Te(IV) and Te(VI) of 86.0-108% and 87.1-97.4%, respectively.

Optical properties of AsSe 1.5− xTe x glassy system

Thin AsSe 1.5− x Te x films with 0⩽ x<1.5 have been prepared by a thermal vacuum evaporation technique onto quartz and glass substrates kept at room temperature (∼300 K) . The optical constants, the refractive index, n, and the absorption index, k, of the films were determined for the investigated compositions of different thickness values (100– 300 nm ) using spectrophotometric measurements of the transmittance, T, and the reflectance, R, at normal incidence in the spectral range 400– 2500 nm . The obtained values of both n and k were found to be independent of the film thickness within the above mentioned thickness range. The estimated indirect and direct optical energy gap decreased as tellurium content increased in the parent sample AsSe 1.5. The values of dispersion energy, E d, and lattice dielectric constant, ε L, of the system have been determined and correlated with the type and amount of chemical bonds and the relative proportion of the constituent elements in the examined compositions.

Optical and electrical properties of C60Tex films

The structure, composition, and electrical and optical properties of thin tellurium-intercalated fullerene films C60Tex are investigated. The samples of compositions from C60Te0.1 to C60Te6 are prepared by thermal evaporation. The sample composition and the impurity distribution are controlled by the Rutherford backscattering technique. The Raman vibrational spectra indicate changes in the symmetry of a C60 molecule: the strain of the molecule increases with a decrease in the tellurium concentration and decreases as the tellurium impurity concentration increases. The evolution of the optical absorption spectra and the electrical conductivity suggests that intercalation of a tellurium impurity leads to modification of the electronic structure of the material. This process is accompanied by a shift and change in shape of the optical absorption edge and a change in the electrical conductivity of films by several orders of magnitude depending on the composition. The electrical conductivity is minimum at a low tellurium impurity content.

Production of dimethyl telluride and elemental tellurium by bacteria amended with tellurite or tellurate

AbstractThe purpose of this study was to determine whether a facultative anaerobe, Pseudomonas fluorescens K27, would produce dimethyl telluride when anaerobic cultures were amended with differing concentrations of sodium tellurate and/or sodium tellurite and how that volatile organotellurium production varied over time. Batch bacterial bioreactor experiments were undertaken in order to observe the changes in the headspace of a growth medium solution inoculated with P. fluorescens and amended with tellurium salts. Gas samples were taken from the bioreactor every hour and were analyzed by capillary gas chromatography using fluorine‐induced chemiluminescence detection to determine compounds in the headspace. Liquid samples were analyzed by spectrophotometer to determine optical densities, which were used as an indicator of cell growth. Verification of the identity of the dimethyl telluride produced in the bacterial headspace above a tellurate‐amended culture was achieved by comparison with the chromatographic retention time of an authentic (CH3)2Te standard and by gas chromatography/mass spectrometry. The time course production of dimethyl telluride varied with amendment salts' tellurium oxidation states and concentrations. Increasing tellurate concentrations caused slower bacterial growth, but those cultures reached the stationary phase sooner than cultures amended with tellurite concentrations 10 or 100 times less. Black elemental tellurium (Te0) was produced by live cultures amended with tellurium salts but not by sterile controls. The amount of tellurium in the solid phase (as Te0 and in/or on cells) harvested from replicate, anaerobic cultures of P. fluorescens sampled after 92 h of incubation was approximately 34%. Mixed tellurite/tellurate amendment experiments exhibited a synergistic toxic effect and yielded less final biomass and very little dimethyl telluride production compared with cultures amended with either tellurate or tellurite alone. Copyright © 2001 John Wiley &amp; Sons, Ltd.

Determination of tellurium in indium antimonide semiconductor material by electrothermal atomic absorption spectrometry.

A method for the determination of the dopant concentration of tellurium in dissolved indium antimonide semiconductor material by electrothermal atomic absorption spectrometry (ETAAS) was developed. Efforts were made to investigate the optimal conditions of the furnace heating program and the effect of palladium modifier on the variation of tellurium and the background absorbance. According to the results obtained, the presence of palladium chemical modifier in the analysis of indium antimonide allowed the successful retention of tellurium in the graphite tube, and the optimum mass of palladium modifier was found to be dependent on the sample matrix concentration. The absorbance profile of tellurium and the background level were significantly improved when a pyrolysis temperature of 1100 degrees C and an atomization temperature of 2200 degrees C were employed in the optimized heating program. With the use of this method, a detection limit of 0.8 microg g(-1) tellurium in indium antimonide could be achieved. The applicability of the proposed method was evaluated by comparison with two independent methods, i.e. slurry sampling-ETAAS and ICP-MS. From the good agreement between the results, it was demonstrated that the proposed method is suitable for the determination of typical dopant concentrations of tellurium in indium antimonide.

Hexagonal approximants of a dodecagonal tantalum telluride — the crystal structure of Ta21Te13

The structure of a hexagonal approximant of the dodecagonal tantalum telluride dd-Ta1.6Te was studied by means of high resolution transmission electron microscopy and electron diffraction. A hierarchical building principle underlying the structures of two other approximants, Ta97Te60 and Ta181Te112, was applied in order to deduce the crystal structure of the approximant with highest tellurium content, Ta21Te13.

Petrography, mineralogy and geochemistry of the Zarshuran Carlin-like gold deposit, northwest Iran

Gold mineralisation at Zarshuran, northwestern Iran, is hosted by Precambrian carbonate and black shale formations which have been intruded by a weakly mineralised granitoid. Granitoid intrusion fractured the sedimentary rocks, thereby improving conditions for hydrothermal alteration and mineralisation. Silicification is the principal hydrothermal alteration along with decalcification and argillisation. Three hydrothermal sulphide mineral assemblages have been identified: an early assemblage of pyrrhotite, pyrite and chalcopyrite; then widespread base metal sulphides, lead-sulphosalts and zoned euhedral arsenical pyrite; and finally late network arsenical pyrite, massive and colloform arsenical pyrite, colloform sphalerite, coloradoite, and arsenic–antimony–mercury–thallium-bearing sulphides including orpiment, realgar, stibnite, getchellite, cinnabar, lorandite and a Tl-mineral, probably christite. Most of the gold at Zarshuran is detectable only by quantitative electron microprobe and bulk chemical analyses. Gold occurs mainly in arsenical pyrite and colloform sphalerite as solid solution or as nanometre-sized native gold. Metallic gold is found rarely in hydrothermal quartz and orpiment. Pure microcrystalline orpiment, carbon-rich shale, silicified shale with visible pyrite grains and arsenic minerals contain the highest concentrations of gold. In many ways Zarshuran appears to be similar to the classic Carlin-type sediment-hosted disseminated gold deposits. However, relatively high concentrations of tellurium at Zarshuran, evidenced by the occurrence of coloradoite (HgTe), imply a greater magmatic contribution in the mineralising hydrothermal solutions than is typical of Carlin-type gold deposits.

Compositional Dependence of Hardness in ZnSe1-xTex and BeyZn1-ySe1-xTex

Hardness characteristics were investigated on ZnSe1-xTex (0≤x≤0.06) and BeyZn1-ySe1-xTex (0≤x≤0.11, 0≤y≤0.10) bulk single crystals, which were grown by the vertical traveling solvent method using a tellurium solution. ZnSe-related mixed crystals containing tellurium and beryllium were harder than the binary ZnSe crystals due to their larger covalent binding energy. The values of the Vickers hardness showed 2.5 GPa for a ZnSe0.94Te0.06 crystal and 4.3 GPa for a Be0.10Zn0.90Se0.89Te0.11 crystal, compared to 1.1 GPa for a ZnSe crystal. The hardening effect by beryllium is estimated to be twice as effective as that by tellurium. The hardness of the mixed semiconductor crystals was expressed by the concentration of tellurium and beryllium to the 1/2 power. The 1/2 power law in mixed crystals should be clarified, considering the shear moduli related to the ionicity. The minimum etch pit density was 3.0×105/cm2 in a BeyZn1-ySe1-xTex crystal. This may be due to large compositional variations in the mixed crystals, which may influence the hardening effect.

Fast electrodeposition route for cadmium telluride solar cells

In this work the possibility to increase markedly the electrodeposition rate of cadmium telluride has been investigated. After a theoretical analysis which has allowed to fix new electrodeposition conditions, based on an increase of the tellurium concentration, a complete experimental study has been carried out with varying the deposition parameters (composition, pH, potential, hydrodynamic regime). The films, deposited at rates up to 17 micron per hour, have been characterized before and after annealing. Results on cell formation with CdS show that junction formation occurs even for high deposition rates. Efficiencies around 6% (700 mV, 18.1 mA cm−2) have been obtained for films grown at 2.7 μm/h.

Pulsed laser deposition of PbTe films on glass substrates

PbTe thin films were prepared by pulsed laser deposition from a Nd:YAG laser (532 nm). The films were deposited on glass substrates. The influence of deposition temperature (80–160 °C), fluence (5–13 J/cm2) and nominal composition of the target on the chemical composition of the films was studied. It was found that the tellurium content of the film is strongly dependent on both the laser fluence and the deposition temperature. Highly textured stoichiometric films can be obtained with suitable conditions.

Concentrations of 63 elements in cabbage and sprouts in Denmark

The multi‐element levels (μg kg‐1, fresh weight) in cabbages (Brassica oleracae L. var. capitata, Scandic) and sprouts (Brassica oleracae L. var. Gemmifera, Explorer) are presented in this paper. The cabbages and sprouts were collected from 10 background areas for each crop, on Funen, in North Jutland, Central Jutland, South East Jutland, and North Zealand, Denmark. The crops were cultivated with intensive use of fertilizers and pesticides. High Resolution Inductively Coupled Plasma Mass Spectrometry (HR‐ICPMS) was used for analyses of the samples. Mean concentrations of the elements were compared with those reported previously from different other surveys. For the alkaline metals [lithium (Li), rubidium (Rb), and cesium (Cs)], Li showed a higher concentration in cabbage than in sprouts. For Rb and Cs the pattern was opposite. For the earth alkaline metals [magnesium (Mg), strontium (Sr), and barium (Ba)], the Mg concentration level was higher in sprouts than in cabbage, and Sr and Ba showed the opposite pattern. The concentrations of boron (B), silicon (Si), phosphorus (P), sulfur (S), selenium (Se), and tellurium (Te), were higher in sprouts than in cabbage, except for Te, in which the concentrai ion in cabbage was greater than in sprouts. Actinides [thorium (Th) and uranium (U)] and lanthanides [lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu)] showed the pattern with higher concentration in cabbage than in sprouts. Cabbage and sprout gave the pattern lead (Pb) greater than cadmium (Cd) and Cd greater than Pb, respectively, showing that cabbage is a stronger Pb uptaker than sprout and sprout stronger Cd uptaker than cabbage. The results provide useful biological, nutritional and background level information on these crops.

Segregation of tellurium in GaSb single crystals and associated diffusion coefficient in the solute layer

Exceptionally uniform, steady-state tellurium segregation was observed in a GaSb single crystal grown by the submerged heater method. The single crystal was grown at 5 mm/h in a 20 mm diameter silica crucible using a 20 mm diameter 〈1 1 1〉 B seed and with melt encapsulation by NaCl–KCl salt. The axial dopant profile consists of three regions: an initial transient, a steady state uniform region and a last to freeze inhomogeneous portion. In the steady state region, the dopant concentration is equal to the initial tellurium content ( C o) in the melt. The axial tellurium profile was best fitted by the Tiller's equation for diffusion controlled segregation with k=0.37 and D=1.0×10 −5 cm 2/s. The inhomogeneous composition in the last to freeze portion is caused by Marangoni convection which takes place after the baffle separates from the melt. The electrical properties of the crystal were evaluated by Hall measurements and four-point probe technique.

Structure defects and phase transition in tellurium-doped ZnSe crystals

ZnSe crystals grown from the melt by Bridgman method are characterized by the presence of such microstructure defects as pores and solid-phase inclusions, grain boundaries and packing defects of twinning type. Microstructural and X-ray analysis of the grown crystals has shown that optical non-uniformity is mainly due to coherent twinned interlayers related to the phase transition wurtzite (W)→sphalerite (S) on cooling which is incomplete over (0 0 0 1)W‖(1 1 1)S planes. The tellurium dopant affects favorably the optical uniformity and degree of structural perfection of ZnSe(Te) crystals. This is due primarily to the sphalerite structure being completely stabilized during the growth process and the absence of twinning type packing defects (PD). Concentration of tellurium is determined which is sufficient to make complete the W→S phase transition.

Tellurium distribution in copper anode slimes smelting

Tellurium is a common minor constituent of copper anode slimes. The distribution of tellurium between the phases during slimes smelting is an important consideration, both in terms of metal quality and the capture of the oxidized tellurium. In this work, the oxidation by oxygen at 1100 °C of a silver-copper selenide matte containing 2 pct tellurium has been examined. The distribution of tellurium between the phases was determined as the extent of oxidation increased, and the system was modeled using a computational thermodynamics package. Oxidized tellurium was found to report to the slag, with none being removed with the gas. The thermodynamic model predicted, to an acceptable level, the tellurium content of all phases as oxidation progressed. It was used to show that oxidation by air rather than oxygen results in higher residual tellurium levels in silver metal and that the lower the smelting temperature, the greater the extent of tellurium elimination from silver to the slag.

Extractive Separation of Selenium and Tellurium Using 2,3,5-Triphenyltetrazolium Chloride

Abstract A simple and selective solvent-extraction method has been devised for the separation of SeIV and TeIV, not only from each other, but also from the other accompanying elements. 2,3,5-Triphenyltetrazolium chloride has been used as an extractant for the quantitative extraction of TeIV and SeIV from bromide and thiocyanate medium, respectively. The formed ion-pair complex of TeIV and SeIV can be quantitatively extracted into a dichloromethane and 1 : 1 cyclohexanol–toluene solvent mixture, respectively. The optimum conditions have been evaluated based on a critical study of the acid concentration, extractant concentration, period of equilibration, effect of dilution and effect of the solvent. Water was used for the stripping of tellurium, while a fresh solution of sodium hypobromite was used for selenium. This separation procedure in conjunction with the developed methods was applied to an analysis of the selenium and tellurium content of copper concentrate, incineration ash and In–Sb alloy samples.

Photosensitivity of thin-film structures based on laser-deposited CuIn(TexSe1−x )2 layers

Thin films of the solid solutions CuIn(TexSe1−x)2 (0<x<1) exhibiting chalcopyrite structure were obtained by the method of laser deposition. Using half-transmitting indium layers, Schottky diodes were prepared on the basis of the films obtained. The spectral dependence of the sensitivity as a function of the ratio between Te and Se was investigated by illuminating the structures through the In contact. Analysis of the experimental results showed that the region of spectral sensitivity of such thin-film structures depends on the tellurium content in the CuIn(TexSe1−x)2 layers.