Showing papers on "Antimony published in 2008"

Enhanced thermoelectric figure-of-merit in p-type nanostructured bismuth antimony tellurium alloys made from elemental chunks.

Abstract: By ball milling alloyed bulk crystalline ingots into nanopowders and hot pressing them, we had demonstrated high figure-of-merit in nanostructured bulk bismuth antimony telluride. In this study, we use the same ball milling and hot press technique, but start with elemental chunks of bismuth, antimony, and tellurium to avoid the ingot formation step. We show that a peak ZT of about 1.3 in the temperature range of 75 and 100 °C has been achieved. This process is more economical and environmentally friendly than starting from alloyed bulk crystalline ingots. The ZT improvement is caused mostly by the lower thermal conductivity, similar as the case using ingot. Transmission electron microscopy observations of the microstructures suggest that the lower thermal conductivity is mainly due to the increased phonon scattering from the increased grain boundaries of the nanograins, precipitates, nanodots, and defects. Our material also exhibits a ZT of 0.7 at 250 °C, similar to the value obtained when ingot was used. This study demonstrates that high ZT values can be achieved in nanostructured bulk materials with ball milling elemental chunks, suggesting that the approach can be applied to other materials that are hard to be made into ingot, in addition to its advantage of lower manufacturing cost.

Intrinsic and extrinsic diffusion of phosphorus, arsenic, and antimony in germanium

Abstract: Diffusion experiments of phosphorus (P), arsenic (As), and antimony (Sb) in high purity germanium (Ge) were performed at temperatures between 600 and 920 °C. Secondary ion mass spectrometry and spreading resistance profiling were applied to determine the concentration profiles of the chemically and electrically active dopants. Intrinsic and extrinsic doping conditions result in a complementary error function and box-shaped diffusion profiles, respectively. These profiles demonstrate enhanced dopant diffusion under extrinsic doping. Accurate modeling of dopant diffusion is achieved on the basis of the vacancy mechanism taking into account singly negatively charged dopant-vacancy pairs and doubly negatively charged vacancies. The activation enthalpy and pre-exponential factor for dopant diffusion under intrinsic condition were determined to 2.85 eV and 9.1 cm2 s−1 for P, 2.71 eV and 32 cm2 s−1 for As, and 2.55 eV and 16.7 cm2 s−1 for Sb. With increasing atomic size of the dopants the activation enthalpy dec...

Direct electrodeposition of Cu2Sb for lithium-ion battery anodes.

Abstract: We describe the direct single potential electrodeposition of crystalline Cu2Sb, a promising anode material for lithium-ion batteries, from aqueous solutions at room temperature. The use of citric acid as a complexing agent increases the solubility of antimony salts and shifts the reduction potentials of copper and antimony toward each other, enabling the direct deposition of the intermetallic compound at pH 6. Electrodeposition of Cu2Sb directly onto conducting substrates represents a facile synthetic method for the synthesis of high quality samples with excellent electrical contact to a substrate, which is critical for further battery testing.

Diffusion and defect reactions between donors, C, and vacancies in Ge. II. Atomistic calculations of related complexes

Abstract: Electronic structure calculations are used to study the stability, concentration, and migration of vacancy-donor (phosphorus, arsenic, and antimony) complexes in germanium, in the presence of carbon. The association of carbon with mobile vacancy-donor pairs can lead to energetically favorable and relatively immobile complexes. It is predicted that the complexes formed between lattice vacancies, carbon, and antimony substitutional atoms are more stable and less mobile compared to complexes composed of vacancies, carbon, and phosphorus or arsenic atoms. Then, with the use of mass action analysis, the relative concentrations of the most important complexes are calculated, which depend also on their relative stability not just their absolute stability. Overall, the theoretical predictions are consistent with experimental results, which determined that the diffusion of vacancy-donor defects is retarded in the presence of carbon, especially in samples with a high concentration of carbon. In addition, the calculations provide information on the structure and the equilibrium concentration of the most important complexes and details of their association energies.

Reduction of antimony by nano-particulate magnetite and mackinawite

Abstract: The speciation of antimony is strongly influenced by its oxidation state (V, III, 0, –III). Redox processes under anaerobic groundwater conditions may therefore greatly alter the environmental behaviour of Sb. Employing X-ray absorption and photoelectron spectroscopy, we show here that Sb(V) is reduced to Sb(III) by magnetite and mackinawite, two ubiquitous Fe(II)-containing minerals, while Sb(III) is not reduced further. At the surface of magnetite, Sb(III) forms a highly symmetrical sorption complex at the position otherwise occupied by tetrahedral Fe(III). The Sb(V) reduction increases with pH, and at pH values >6.5 Sb(V) is completely reduced to Sb(III) within 30 days. In contrast, at the mackinawite surface, Sb(V) is completely reduced across a wide pH range and within 1 h. The Sb(V) reduction proceeds solely by oxidation of surface Fe(II), while the oxidation state of sulphide is conserved. Independent of whether Sb(V) or Sb(III) was added, an amorphous or nano-particulate SbS3-like solid formed.

Characterization of new quaternary chalcogenide As-Ge-Se-Sb thin films

Abstract: This paper reports the effect of replacement of selenium by antimony on the optical gap and some other physical parameters of new quaternary chalcogenide As14Ge14Se72− x Sb x (where x = 3, 6, 9, 12 and 15 at%) thin films. Thin films with thickness 200–220 nm of As14Ge14Se72− x Sb x were prepared by thermal evaporation of the bulk samples. Increasing antimony content was found to affect the average heat of atomization, the average coordination number, number of constraints and cohesive energy of the As14Ge14Se72 −x Sb x alloys. Optical absorption measurements showed that the fundamental absorption edge is a function of composition. Optical absorption is due to allowed, non-direct transition and the energy gap decreases with the increasing antimony content. The chemical bond approach has been applied successfully to interpret the decrease in the optical gap with increasing antimony content.

Measurement of total antimony and antimony species in mine contaminated soils by ICPMS and HPLC-ICPMS

Abstract: This paper describes the measurement of total antimony and antimony species in “real world” mine contaminated sediments using ICPMS and HPLC-ICPMS. Low and high temperature microwave extraction procedures (90 °C and 150 °C, respectively) using a range of nitric–hydrochloric acid combinations were examined as to their efficacy to extract antimony from six mine contaminated soils and a certified reference material. The use of the higher temperature with nitric–hydrochloric acid (1 : 2 (v/v)) was suitable to release antimony from sediments and the certified reference material, NIST 2710 Montana soil. Antimony concentrations obtained using this acid mixture were similar to those obtained using a more aggressive extraction with nitric, hydrochloric, perchloric and hydrofluoric acid mixture. A 25 mM citric acid solution at 90 °C for 15 min extracted 47–78% of antimony from soils. A Hamilton PRP X-100 anion exchange column with 20 mM EDTA mobile phase, pH 4.5, flow rate 1.5 mL min–1 and column temperature of 50 °C was used to separate antimony species. Column recoveries ranged from 78–104%. The predominant form of antimony was Sb5+. Little conversion of Sb5+ occurred (<5%) during extraction, however, significant conversion of Sb3+ occurred (∼36%). The extraction of antimony species with citric acid should be useful in the determination of inorganic antimony available to plants, as plants commonly excrete carboxylic acids, including citric acid, into their rhizospheres to mobilise trace elements for nutritional purposes.

Formation of antimony sulfide powders and thin films from single-source antimony precursors

Abstract: Solvothermal and hydrothermal methods have been employed to generate nano-sized Sb2S3 (stibnites) from a variety of xanthate, dithiocarbamate and dithiophosphate precursors. The solvothermal method allows control of morphology by regulating precursor and size by reaction time; this process also produces near-uniform and larger particles. The xanthate precursors are far superior to the dithiocarbamates in their ability to produce oxide-free Sb2S3. Aerosol-assisted chemical vapour deposition (AACVD) provided a means to produce good quality films of Sb2S3. The advantages of xanthate precursors is rationalised in terms of a facile, low-temperature Chugaev rearrangement.

Amorphous ge/te deposition process

Abstract: Germanium, tellurium, and/or antimony precursors are usefully employed to form germanium-, tellurium- and/or antimony-containing films, such as films of GeTe, GST, and thermoelectric germanium-containing films. Processes for using these precursors to form amorphous films are also described. Further described is the use of [{nBuC(iPrN) 2 } 2 Ge] or Ge butyl amidinate to form GeTe smooth amorphous films for phase change memory applications.

Determination of total antimony and inorganic antimony species by hydride generation in situ trapping flame atomic absorption spectrometry : a new way to (ultra)trace speciation analysis

Abstract: The analytical performance of non-chromatographic coupled hydride generation, integrated atom trap (HG-IAT) atomizer flame absorption spectrometry (FAAS) systems were evaluated for the speciation analysis of antimony in environmental samples. Antimony, using formation of stibine (SbH3) vapors were atomized in an air–acetylene flame-heated IAT. A new design of HG-IAT-FAAS hyphenated technique that would exceed the operational capabilities of existing arrangements (a water-cooled single silica tube, double-slotted quartz tube or an “integrated trap”) was investigated. For the estimation of Sb(III) and Sb(V) concentrations in samples, the difference between the analytical sensitivities of the absorbance signals obtained for antimony hydride without and with previous treatment of samples with L-cysteine can be used. The concentration of Sb(V) was calculated by the difference between total Sbtot and Sb(III). A dramatic improvement in detection limit was achieved compared with that obtained using either of the atom trapping techniques, presented above, separately. This novel approach decreases the detection limit down to low pg mL–1 levels. The concentration detection limit, defined as 3 times the blank standard deviation (3sigma), was 0.2 ng mL–1. For a 120 s in situ pre-concentration time (sample volume of 2 mL), sensitivity enhancement compared to flame AAS, was 550 fold for Sb, using hydride generation-atom trapping technique. The sensitivity can be further improved by increasing the collection time. The precision, expressed by RSD, was 8.0% (n = 6) for Sb. The designs studied include slotted tube, water-cooled single silica tube and integrated atom traps. Reference and real sample materials were analyzed. The accuracy of the method was verified by the use of certified reference materials (NIST SRM 2704 Buffalo River Sediment, SRM 2710 Montana Soil, SRM 1633a Coal Fly Ash, SRM 1575 Pine Needles, SRM 1643e Trace Elements in Water) and by aqueous standard calibration technique (solutions). The measured Sb content, in reference materials, were in satisfactory agreement with the certified values. The hyphenated technique was applied for antimony determinations in soil, sediment, coal fly ash, sewage and river water.

Electrodeposition of tin and antimony in 1-ethyl- 3-methylimidazolium tetrafluoroborate ionic liquid

Abstract: The electrodepositions of Sn(II) and Sb(III) were studied in the [EMIm]BF4 ionic liquid at ambient temperature. Linear sweep voltammetry (LSV) results indicated that the reductions of Sn(II) and Sb(III) on Pt electrode are electrochemically irreversible. The diffusion coefficients of Sn(II) and Sb(III) in the ionic liquid electrolyte were determined in terms of the LSV data. Tin and antimony ions form simpler Sn(II) chlorocomplex species and higher Sb(III) chlorocomplexes, respectively present in the ionic liquid electrolyte. Energy dispersive X-ray spectroscopy (EDX) analysis revealed that tin and antimony alloys can be electroplated in the ionic liquid electrolyte.

Antimony Oxide Hydroxide Ethanedisulfonate: a Cationic Layered Metal Oxide for Lewis Acid Applications

Abstract: We have discovered a rare example of a cationically charged inorganic material. The layered structure is an example outside the extensively studied isostructural set of anionic clays/layered double hydroxides and our previously reported lead fluoride nitrate. For the present compound, the antimony oxide hydroxide layers are positively charged and are templated by anionic alkylenedisulfonate. The organic molecules are only bonded electrostatically to the layers with sulfonate oxygen to antimony distances beyond the covalent range. The material catalyzes a ketal formation reaction as a Lewis acid without the need for drying the solvent before the reaction or a nonaqueous medium such as toluene. The catalyst is heterogeneous and is completely recovered after the catalysis for reapplication.

Sorption of antimony (V) onto synthetic goethite in carbonate medium

Abstract: The sorption kinetics of antimony(V) on synthetic goethite is very fast compared to the sorption of other metals on goethite (e.g. arsenic and selenium) and depends on temperature, with an activation energy of 49±9 kJ · mol−1 in the temperature range 15–35°C. Sorption isotherms have been developed at different temperatures and ionic strength values. The results have been modelled using a Langmuir isotherm and there is not a considerable influence of neither the temperature in the range studied (15°C–35°C), nor the ionic strength (between 0.001 and 0.01 mol · dm−3). Sorption is very high at pH values lower than 8, at more alkaline pH, the sorption decreases with pH, as expected considering the Antimony(V) predominating complex in solution, Sb(OH)6 −. Triple‐layer model successfully describes the data obtained by assuming a bidentate edge‐sharing surface complex of antimonate on the surface of goethite.