Showing papers on "Antimony published in 1996"

Filled Skutterudite Antimonides: A New Class of Thermoelectric Materials

Abstract: A class of thermoelectric materials has been synthesized with a thermoelectric figure of merit ZT (where T is temperature and Z is a function of thermopower, electrical resistivity, and thermal conductivity) near 1 at 800 kelvin. Although these materials have not been optimized, this value is comparable to the best ZT values obtained for any previously studied thermoelectric material. Calculations indicate that the optimized material should have ZT values of 1.4. These ternary semiconductors have the general formula RM4X12 (where R is lanthanum, cerium, praseodymium, neodymium, or europium; M is iron, ruthenium, or osmium; and X is phosphorus, arsenic, or antimony) and represent a new approach to creating improved thermoelectric materials. Several alloys in the composition range CeFe4-xCoxSb12 or LaFe4-xCoxSb12 (0 < x < 4) have large values of ZT.

Mutagenicity, carcinogenicity and teratogenicity of antimony compounds.

Abstract: The paper reviews the information available concerning the mutagenic, teratogenic and carcinogenic effects of antimony. A claim that antimony compounds could have mutagenic properties is based on insufficient and not particularly relevant data. Additional experiments, particularly with organic antimony compounds, would be desirable, but from what we know already, one may be confident that antimony is less a mutagenic risk than many other metals such as As, Cr, Ni, among others. Evidence for a carcinogenic risk of antimony in experimental animals was judged by the IARC sufficient for antimony trioxide and limited for antimony trisulfide. In man, IARC considered antimony trioxide as possibly carcinogenic. However, exposure in all studies on which these conclusions are based also involved other proven or likely carcinogenic compounds. Studies with pure antimony compounds, especially those used in therapy, need to be performed to clarify the situation. Although some indications exist that antimony trioxide could interfere with embryonic and fetal development, the studies seem not entirely conclusive. It is regrettable that, at least to our knowledge, the outcome of pregnancy in women treated with antimony compounds for leishmaniasis has not been studied. In conclusion, it appears that mutagenic, carcinogenic and teratogenic risks of antimony compounds, if they exists at all, are not very important.

Raman scattering study of antimony‐based skutterudites

Abstract: Raman spectra of single‐crystal CoSb3 and RhSb3 and of polycrystalline IrSb3 have been studied. We have also studied four different polycrystalline‐filled skutterudite samples, Ir4LaGe3Sb9, Ir4NdGe3Sb9, Ir4SmGe3Sb9, and Fe4CeSb12, where rare‐earth ions occupy the voids in the skutterudite structure. These void‐filling ions interact with some of the lattice vibrations in this structure and produce a shift and broadening of the observed lines. The most prominent lines in all of the samples are the Sb4 ring‐breathing modes.

Antimony speciation in freshwater plant extracts by using hydride generation?gas chromatography?mass spectrometry

Abstract: An analytical method based on a semi-continuous hydride generator coupled on-line with a gas chromatograph and mass spectrometric detectro was developed and used for the identification of hydride-forming antimony compounds. This method allows for the characterization of compounds based on their retention times and mass spectral data. Organoantimony compounds were identified to be present in extracts of a freshwater plant, namely pondweed (Potamogetan pectinatus). This is the first time that such compounds have been detected in samples of biological origin. The problem of organostibine molecular rearrangements which have been reported to occur during the hydride generation process was also investigated. An experimental procedure is described that allows for the elimination of such rearrangements.

Segregation and diffusion on semiconductor surfaces.

Abstract: The surface segregation of phosphorus, antimony, and boron in Si molecular-beam epitaxy is investigated experimentally at low temperatures. Rate and temperature dependent measurements are explained by a segregation model, which connects surface segregation with surface diffusion. The model is found to explain quantitatively many available data of segregation on different semiconductor surfaces, explicitly: Si, Ge, and GaAs. \textcopyright{} 1996 The American Physical Society.

Diffusion of Sb in relaxed Si1−xGex

Abstract: Diffusion of antimony in relaxed Si1−xGex alloy layers grown by molecular beam epitaxy has been studied as a function of the composition for 0≤x≤0.5. The diffusivity of antimony was found to increase with the Ge alloy content, and the extracted activation energies for diffusion were found to decrease with increasing germanium content in the investigated composition range. The activation energies, however, are significantly higher than the corresponding activation energies obtained by an extrapolation between the activation energy in pure silicon and germanium.

Structural and Quantum Chemical Study of Bi53+ and Isoelectronic Main-Group Metal Clusters. The Crystal Structure of Pentabismuth(3+) Tetrachlorogallate(III) Refined from X-ray Powder Diffraction Data and Synthetic Attempts on Its Antimony Analogue

Abstract: Pentabismuth(3+) tetrachlorogallate(III), (Bi53+)(GaCl4-)3, has been synthesized by reducing a BiCl3−GaCl3 melt with bismuth metal and the crystal structure refined from X-ray (Cu Kα1) powder diffraction data. The structure was found to belong to space group R-3c, with the lattice parameters a = 11.871(2) A and c = 30.101(3) A (Z = 6). It is isostructural with the previously characterized Bi5(AlCl4)3. An attempt to synthesise the antimony analogue Sb5(GaCl4)3 by reducing a SbCl3−GaCl3 mixture with gallium metal produced a black solid phase. The gallium content of this phase is consistent with the stoichiometry Sb5(GaCl4)3, and the Raman spectrum of the phase dissolved in SbCl3−GaCl3 comprises strong, low-frequency bands attributable to Sb−Sb stretch vibrations in Sb53+ or another reduced antimony species. Quantum chemical analyses have been performed for the isoelectronic, trigonal pyramidal closo-clusters Sn52-, Sb53+, Tl57-, Pb52-, and Bi53+, both with extended Huckel (eH) and Hartree−Fock (HF) methods....

Atomic antimony for molecular beam epitaxy of high quality III–V semiconductor alloys

Abstract: The product distribution of an antimony cracking effusion cell has been characterized using a time‐of‐flight mass spectrometer employing resonance‐enhanced laser ionization. Source operating conditions have been identified under which predominately tetramers, dimers, and monomers of antimony are produced. Molecular beam epitaxy experiments employing the characterized antimony source for the growth of antimonide/arsenide superlattices and GaSb epilayers show that significant improvements in material quality can be obtained using monomeric antimony over that using molecular antimony species. A comparison of the surface chemistry of atomic and diatomic antimony species in the growth of several Sb‐containing semiconductors will be presented.

Spectrochemical trace analysis for metals and metalloids

Abstract: Part 1 General: sampling decomposition - dissolution techniques separation and preconcentration spectrometric determination techniques quantification techniques speciation analysis flow-injection analysis quality assurance in trace analysis. Part 2 Multielement trace analysis of real samples: biological and clinical materials inorganic industrial materials organic industrial materials. Part 3 Determination of individual elements: aluminium antimony arsenic barium beryllium bismuth boron cadmium caesium calcium and magnesium chromium cobalt copper gallium germanium gold hafnium indium iron lead lithium manganese mercury molybdenum nickel niobium osmium palladium platinum rare earth elements rhenium rhodium rubidium ruthenium scandium selenium silicon silver sodium and potassium strontium tantalum technetium tellurium thallium thorium tin titanium transuranium elements tungsten uranium vanadium zinc zirconium.

Low-voltage varistors based on zinc antimony spinel zn7sb2o12

Abstract: It is possible to prepare low‐voltage varistors from the zinc antimony spinel Zn7Sb2O12 with breakdown voltages in the range of 3–20 V and nonlinearity coefficient α=7–15. The varistor property is due to the formation of high ohmic potential barriers at the grain boundary regions on low‐ohmic n‐type grain interiors of the polycrystalline samples. The method of preparation of the spinel, synthesized by coprecipitation followed by annealing under restricted partial pressures of oxygen, controls the mixed valence states for antimony, namely, Sb3+ and Sb5+. This is critical in attaining high nonlinearity and lower breakdown voltages.

Dinuclear and Tetranuclear Cages of Oxodiphenylantimony Phosphinates: Synthesis and Structures.

Abstract: The novel dimeric compounds [Ph2Sb(O2PR2)O]2·2CH2Cl2 [R = cycl-C6H11 (2) and cycl-C8H15 (3)] have been synthesized by reacting diphenylantimony trichloride (1) with 3 mol equiv of silver acetate followed by 1 mol equiv of the phosphinic acid. By the same route under more stringent conditions to exclude moisture, the mixed phosphinate−acetate [Ph2Sb(O2P(C6H11)2)(O2CMe)]2O (4) was isolated and characterized. Treatment of 2 with acetic acid/water affords the tetranuclear cage Ph8Sb4O4(OH)2(O2P(C6H11)2)2·CH3COOH·CH2Cl2 (5); it is possible to convert 5 to 2 by heating it with an excess of the phosphinic acid. Compounds 2, 3, and 5 have been characterized by X-ray structural analysis. All of them possess four membered Sb2O2 rings with hexacoordinated antimony. In 5 the antimony atoms in the two Sb2O2 rings are connected by oxo bridges on two sides to give an Sb4O6 cage. These structures are correlated with those of known tin cages.

Synthesis and Solution Spectral Properties of Antimony(III) Phthalocyanine and Dihydroxoantimony(V) Phthalocyanine Complexes

Abstract: A straightforward synthesis of (phthalocyaninato)antimony(III) fluoride and the corresponding dihydroxoantimony(V) phthalocyanine complex is reported. Both low- and high-valent compounds are well soluble in polar media without aggregation. The redox properties and the electronic absorption as well as luminescence spectra of these metalloid phthalocyanines are investigated for the first time in some detail.

Preparation, characterization and ab initio computation of the first binary antimony azide, Sb(N3)3

Abstract: Reaction of SbI3 with silver azide in acetonitrile solution gave Sb(N3)3 in high yield The product was separated from silver iodide by extraction with acetonitrile The identity of this first binary antimony azide was established by 14N NMR and IR spectroscopy The molecular structure of Sb(N3)3 was computed ab initio at the Hartree–Fock (HF) level of theory (HF/6–31 + G*) using a quasi-relativistic pseudo-potential (ECP) for antimony The calculated and observed IR frequencies are in reasonable agreement

Comparison of systems for eliminating interferences in the determination of arsenic and antimony by hydride generation inductively coupled plasma atomic emission spectrometry

Abstract: The determination of arsenic and antimony by hydride generation inductively coupled plasma atomic emission spectrometry is discussed. A comparison is made of different procedures for eliminating redox (HNO3) and transition metal interferences; two pre-reduction agents, three continuous-flow systems and two gas–liquid separators were studied. The pre-reduction agents were KI and thiourea, which were added in a continuos-flow mode either before or after the introduction of tetrahydroborate. The spray chamber served as a gas–liquid separator; alternatively a U-tube separator was used. In the recommended system, 10% m/v thiourea is added to the sample stream before 1.0% m/v tetrahydroborate is introduced, using the spray chamber as a gas–liquid separator. Thiourea eliminated the oxidation interference from HNO3 and also the interference from 50 mg l–1 of Ag+, Cu2+, Ni2+ and Fe3+.

Trace analysis of antimony (III) and antimony (V) by adsorptive stripping voltammetry

Abstract: A sensitive and selective adsorption stripping voltammetric (AdSV) method for the determination of antimony using chloranilic acid (2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone) as complexing reagent is described. The conditions under which its species of both oxidation states, Sb(III) and Sb(V), can be detected have been established. Sb(III) can be adsorbed onto the hanging mercury drop electrode (HMDE) using an accumulation potential of +100 mV from hydrochloric acid (pH=3.0) solution. Sb(V) can be determined using an accumulation potential of −500 mV in HCl (pH=1.0) solution. The peak potentials in the stripping voltammograms are −400 mV for Sb(III) and −140 mV for antimony (V). The detection limits are 210 ng/L for Sb(III) with 5 min pre-concentration and 560 ng/L for Sb(V) with 10 min pre-concentration. The method is applicable to the trace analysis and speciation of antimony in water samples and phosphoric acid.

Synthesis of a novel two-dimensional antimony sulfide, [C4H10N]2[Sb8S13].0.15H2O, and its structure solution using synchrotron/imaging plate data

Abstract: A novel antimony sulfide, [C4H10N]2[Sb8S13]·0.15H2O, was synthesized hydrothermally, and its structure was determined from data collected using a synchrotron/imaging plate system. The new compound consists of centrosymmetric Sb16S264- planar clusters. Each cluster is connected to four others through two edge-sharing and two corner-sharing SbS3 pyramids, forming an extended sheet. The protonated pyrrolidine molecules reside between the parallel stacked sheets. The structure is triclinic (space group P1) with a = 6.929(2) A, b = 16.747(2) A, c = 17.976(4) A, α = 94.84(1°), β = 95.41(1)°, and γ = 125.28(1)°.

Effects of 2-picoline on zinc electrowinning from acidic sulfate electrolyte

Abstract: The behaviour of 2-picoline with and without antimony during electrowinning of zinc from acidic sulfate solutions was studied and was compared with that of gum arabic which is commonly used in industry as a levelling agent. The effects of these additives on current efficiency, power consumption, deposit quality, polarization behaviour, crystallographic orientation and surface morphology were determined. The addition of 2-picoline reduced current efficiency, increased power consumption and lowered the surface quality of electrowon zinc. Addition of antimony increased current efficiency, reduced power consumption and produced improved surface morphology and crystal orientations, (101) (112) (102) (103) (114) over a wide range of their combinations.

A Novel Antimony Sulfide Templated by Dimethylammonium: Its Synthesis and Structural Characterization Using Synchrotron/Imaging Plate Data

Abstract: Hydrothermal synthesis at 200 °C produced a new open antimony sulfide framework, [C2H8N]2[Sb8S12(S2)], designated DMA-SbS-SB8. The structure (Cmca, a = 9.9704(7), b = 11.652(2), and c = 25.979(3) A), determined from data collected on a small single crystal (20 × 30 × 40 μm in size) utilizing the synchrotron/imaging plate system installed at the X3A1 beamline of the NSLS, consists of [Sb8S12(S2)]2- double chains formed from Sb4S72- single chains joined through S−S bridges. The double chains contain 18-membered Sb8S10 rings and are interlocked to form sheets perpendicular to the b axis. Dimethylammonium ions, assumed to be protonated to charge balance the anionic [Sb8S12(S2)]2- framework, reside within 18-membered rings. The structural building units of the new open framework are similar to those described previously in other members of the antimony sulfide system. Experiments carried out at different temperatures and reaction times show that DMA-SbS-SB8 is formed from a distinct poorly crystallized phase (...

Method for coating a metal strip

Abstract: A corrosion-resistant metal strip and method for making the same which is essentially lead free and is not highly reflective. The coating on the metal strip is a two-phase metallic coating comprised of tin and zinc and a very low weight percentage of lead. The coating alloy may also include antimony, bismuth and copper to improve the coating process and/or improve the properties of the tin and zinc coating. A metal layer may also applied to the surface of the metal strip prior to applying the metallic alloy coating.

Tin-bismuth based lead-free solder for copper and copper alloys

Abstract: Lead-free alloys for use as solders for copper and copper alloys. In the alloys, tin (Sn) and bismuth are the basic components and either one or both of antimony (Sb) and zinc (Zn) may be added as major elements to yield a low melting temperature alloy, and small quantities of one or more of aluminum (Al), magnesium (Mg) and tellurium (Te) may be added as elements capable of improving a soldering characteristics and properties of alloy. In preferred embodiments, the alloys contain bismuth (Bi) in a range of 1.0-20 wt %, and one or more of antimony (Sb) in the range of 0.1-8.0 wt %, more preferably 0.1-3.0 wt %, zinc (Zn) in a range of 0.01-3.0 wt %, aluminum (Al) in a range of 0.01-3.0 wt %, magnesium (Mg) in a range of 0.01-3.0 wt %, and tellurium (Te) in a range of 0.01-3.0 wt %, the balance being tin (Sn).

Method of recovering antimony and bismuth from copper electrolyte

Abstract: A method of recovering antimony and bismuth from copper electrolyte comprises the steps of immersing a pure copper material in the copper electrolyte, so that the iron ions are reduced from Fe3+ ions to Fe2+ ions, using a mixture of dilute sulfuric acid and sodium chloride adjusting the acidity or acidic concentration, to selectively elute the bismuth and antimony wherein if the final concentration of bismuth is adjusted to be 0.02 g/l or less in the bismuth election, it is possible to keep the maximum concentration of bismuth in the antimony eluate in the elution of antimony after selective bismuth elution to 0.01 g/l or less.

Sb LIII-edge XAS study of the ternary system Sb2S3As2S3Tl2S

Abstract: The local environment of antimony atoms in glassy samples of the system Sb2S3As2S3Tl2S is studied by X-ray absorption spectroscopy at the Sb LIII-edge. The crystalline compound TlSb3S5, situated within the zone of glass formation of the Sb2S3As2S3Tl2S phase diagram, is used as reference compound in order to derive appropriate phase and amplitude functions for the extended X-ray absorption fine structure (EXAFS) study. The limits of EXAFS in studying the local order around antimony in compounds with complex structure are discussed. The possibilities of a combined application of EXAFS, X-ray absorption near edge structure and 121Sb Mossbauer spectroscopy to the study of these compounds are shown. The results are discussed in terms of a model of random substitution of arsenic by antimony.