Showing papers on "Antimony published in 1993"

Blackening of tin oxide thin films heavily doped with antimony

Abstract: The electrical and optical properties of tin oxide (SnO2) thin films heavily doped with antimony (Sb) have been investigated. The films were prepared by spray pyrolysis at a temperature of 500°C. An undoped SnO2 film is transparent and its resistivity is 4 × 10−3 Ω cm. With increase in antimony content the resistivity initially decreases and then begins to increase. The decrease in the resistivity can be attributed to the substitutional doping by pentavalent antimony Sb5+, whereas the increase in the resistivity can be attributed to the substitutional doping by trivalent antimony Sb3+. The films become opaque with increasing antimony content and finally tum black. The interaction between antimony in the two different oxidation states in the SnO2 lattice is responsible for the blackening of the films.

L-Cysteine as a reducing and releasing agent for the determination of antimony and arsenic using flow injection hydride generation atomic absorption spectrometry—Part 1. Optimization of the analytical parameters

Abstract: L-Cysteine was investigated as the reducing and releasing agent for the determination of antimony and arsenic using flow injection hydride generation atomic absorption spectrometry with the aim of replacing the previously used potassium iodide. The prereduction of the pentavalent to the trivalent form at room temperature was completed within 5 and 30 min for antimony and arsenic, respectively, which was essentially identical with the performance of potassium iodide. However, much lower acid and reagent concentrations were required with L-cysteine than with potassium iodide. In addition, even dilute analyte solutions containing L-cysteine were stable for at least one week, whereas solutions containing potassium iodide had to be prepared fresh daily. Under optimized conditions, in the presence of 1% m/v L-cysteine and 1 mol l–1 HCI for antimony or 0.1 mol l–1 HCI for arsenic, detection limits (three times the standard deviation of a blank solution, n= 10) of 0.05 and 0.01 µg l–1 were obtained for antimony and arsenic. The calibration graphs were linear (r > 0.999) for up to 10 µg l–1 of antimony and 5 µg l–1 of arsenic, using integrated absorbance for evaluation. The precision was better than 2% relative standard deviation (n= 10) for both elements at the 5 µg l–1 concentration level.

L-Cysteine as a reducing and releasing agent for the determination of antimony and arsenic using flow injection hydride generation atomic absorption spectrometry?Part 2. Interference studies and the analysis of copper and steel

Abstract: A method was developed for the determination of antimony and arsenic in copper and steel using flow injection hydride generation atomic absorption spectrometry (FI-HGAAS) and L-cysteine as reducing and releasing agent. Tolerance limits (less than 10% interference) of at least 250 and 500 mg l–1 were found for nickel and copper, respectively, in the presence of 1% m/v L-cysteine, in the determination of antimony. For the determination of arsenic the corresponding tolerance limits were 200 mg l–1 for nickel and more than 1000 mg l–1 for copper. Only 100 mg l–1 of copper could be tolerated when potassium iodide was used for reduction. Higher copper concentrations resulted in precipitation of copper(I) iodide, which caused severe contamination of the conduits of the FI system. L-Cysteine is, therefore, recommended for FI-HGAAS because of its better performance for the determination of antimony and arsenic and because of the much lower acid concentrations required. Very good agreement with the certified values for antimony and arsenic in copper and steel National Institute of Standard and Technology Standard Reference Materials was obtained, on addition of L-cysteine, by calibration with matrix-free standard solutions, using the bracketing technique.

Reversible rotation of antimony dimers on the silicon (001) surface with a scanning tunneling microscope.

Abstract: The scanning tunneling microscope (STM) was used to control the configuration of antimony clusters on the (001) surface of silicon. In particular, the STM tip induced a reversible rotation between two orthogonal orientations of individual antimony dimers on the surface. This simple rotation can be explained by an atomic-scale torque exerted on the antimony dimers by the STM tip. The reversibility of this process could provide a basis for making atomic-scale memory cells.

Multimetal oxide compositions and process of preparing same

Abstract: Multimetal oxide compositions of the formula I [X.sup.1.sub.a X.sup.2.sub.b O.sub.x ].sub.p [X.sup.3.sub.c X.sup.4.sub.d X 5 e X 6 f X 7 g X 2 h O y ] q (I) where X 1 is bismuth, tellurium, antimony, tin and/or copper, X 2 is molybdenum and/or tungsten, X 3 is an alkali metal, thallium and/or samarium, X 4 is an alkaline earth metal, nickel, cobalt, copper, manganese, zinc, tin, cadmium and/or mercury, X 5 is iron, chromium, cerium and/or vanadium, X 6 is phosphorus, arsenic, boron and/or antimony, X 7 is a rare-earth metal, titanium, zirconium, niobium, tantalum, rhenium, ruthenium, rhodium, silver, gold, aluminum, gallium, indium, silicon, germanium, lead, thorium and/or uranium, a is from 0.01 to 8, b is from 0.1 to 30, c is from 0 to 4, d is from 0 to 20, e is from 0 to 20, f is from 0 to 6, g is from 0 to 15, h is from 8 to 16, x and y are numbers determined by the valency and frequency of the elements in I other than oxygen, and p and q are numbers whose ratio p/q is from 0.1 to 10, containing three-dimensional regions with a chemical composition X 1 a X 2 b O x which are delimited from their local environment due to their chemical composition which is different from their local environment, and whose maximum diameter is from 1 to 25 μm.

Effect of dopant incorporation on structural and electrical properties of sprayed SnO2:Sb films

Abstract: Antimony‐doped tin oxide films were deposited by spray pyrolysis technique. The effect of antimony doping on structural and electrical properties was investigated in detail using the x‐ray diffraction technique and room‐temperature Hall measurements. Antimony doping did not affect the preferred growth along [200] to a considerable extent. These results were analyzed on the basis of structure factor calculations. From the Hall measurements, the lowest electrical resistivity, i.e., 5.2×10−4 Ω cm was observed for the films with a doping level of 2.3 at. % in the solution. This value of electrical resistivity is the lowest reported so far in the case of spray deposited antimony‐doped SnO2 films. The grain boundary and ionized impurity scattering were observed to be prevalent in governing the electronic transport of lightly and heavily doped films, respectively.

Surfactant‐mediated growth of germanium on silicon (001) with submonolayer coverage of Sb and Te

Abstract: Surfactant‐mediated growth of germanium on silicon (001) with submonolayer coverages of antimony and tellurium, respectively, was investigated with reflection high‐energy electron diffraction and transmission electron microscopy. Approximately 0.2 monolayer of antimony is needed for a complete suppression of islanding for the growth at 450 °C. For growth at a lower temperature (270 °C), only approximately 10% of a monolayer antimony or tellurium is needed in order to obtain smooth epitaxial germanium layers. No differences could be detected between tellurium and antimony in the behavior as a surfactant. The performed surfactant‐mediated growth experiments can be understood as the kinetic suppression of islanding due to a reduction in surface diffusion of germanium adatoms.

Oxygen Solubilities in Si Melt: Influence of Sb Addition

Abstract: The oxygen solubility in liquid silicon, both undoped and Sb-doped, in equilibrium contact with SiO2 has been analyzed after quenching by the SIMS (secondary ion mass spectroscopy) technique in order to investigate the influence of antimony addition on the oxygen solubility. It has been shown that oxygen solubility in undoped silicon melt increases from 2.08×1018 to 2.29×1018 atoms/cm3 upon temperature increases from 1447 to 1542°C. The influence of antimony addition in the same temperature range was twofold. Addition of less than 1 at.% Sb caused practically no change in oxygen solubility, while addition of more than 1.3 at.% Sb appreciably increased both its level and its temperature coefficient.

Flash memory cell having antimony drain for reduced drain voltage during programming

Abstract: An improved ETOX-type flash memory cell which requires only a single 5-volt power supply for read, write and erase functions. By substituting antimony or the combination of antimony and arsenic for the usual arsenic drain dopant, drain junction depth is reduced, due to the low diffusivity of antimony during high-temperature cycling. In order to maximize the concentration of antimony in the drain region, which is limited to approximately 3×10 19 atoms/cm 3 (due to solid solubility characteristics of antimony at standard silicon process activation temperatures in the 800°-1,000° C. range), an antimony implant concentration of approximately 1×10 15 atoms/cm 2 is employed. The resulting shallow junction raises the electric field strength at the cell's drain junction, thus increasing the hot electron generation rate and improving the programming efficiency. The decreased junction depth also acts to improve short channel effects such as punch-through and drain-to-gate capacitive coupling. The addition of a boron halo implant to obtain a traditional doubly diffused drain further enhances programming efficiency.

Study of some interfering processes in the arsenic, antimony and selenium determination by hydride generation atomic absorption spectrometry

Abstract: A detailed study of interfering processes in the determination of As, Sb and Se using a twin-channel hydride generation flow-system is presented. The influence of As, Sb, Se and Sn on all three studied elements has a similar character and occurs in the gas phase only. In the presence of bismuth and tellurium interferences occur also in the liquid phase. It was found that arsenic and antimony may influence the analytical signals of elements with analytical lines in the range from 190 to 235 nm by non-specific absorption due to molecular band spectra.

121-Sb Mössbauer study of insulating and ion-conducting antimony chalcogenide-based glasses

Abstract: The local environment of antimony in As2S3Sb2S3, AgISb2S3, AsSbSe and A AgAsSbSe glasses, glassy/crystalline alloys and crystals is investigated using 121-Sb Mossbauer spectroscopy. The isomer shift both for sulfide and selenide vitreous alloys is 1.2–2.0 mm/s more positive than that for corresponding crystalline parents. The smaller s-electron density at the 121Sb nucleus for glasses indicates a decrease of the antimony-chalcogen interatomic distances in comparison with those for crystalline materials. The isomer shift systematics and composition dependencies of the electric-quadrupole coupling constant, eQVzz, and the asymmetry parameter, ν, shows that in As2S3Sb2S3 and AsSbSe insulating glasses an isomorphous substitution of arsenic by antimony occurs accompanied by an increase of interatomic distances. In the case of Ag+ ion-conducting vitreous alloys, however, the antimony-chalcogen distances are governed by the silver content and do not depend on the Sb fraction of the glass. Geometric and topological disorder in the glass network is correlated with an increase of the electric-quadrupole coupling constants and values of the asymmetry parameter ν between 0.4 and 1.0.

Influence of additives on the electrical properties of dense SnO2‐based ceramics

Abstract: Highly densified 0.99 SnO2‐0.01 CuO‐based ceramics with antimony, tantalum, or niobium oxides as additives have been prepared. Samples have been characterized by dc conductivity and complex impedance spectroscopy as a function of temperature and by current density as a function of electric field. Microstructures have been analyzed by scanning electron microscopy, electron microprobe, and Auger spectroscopy. The electrical properties of Ta‐ and Nb‐doped ceramics are grain boundary controlled at least at low temperature. Sb‐doped materials show a different electrical behavior due to the presence of a segregation layer of antimony which inhibits grain boundary effects.

Ion-beam-induced atomic transport and phase formation in the system nickel/antimony

Abstract: Sb/Ni multilayers of 200 nm total thickness were ion-beam mixed with 900 keV Xe++ or 600 keV Ar++ ions using fluences up to 1016 ions/cm2. The formation of crystalline intermetallic phases was observed by X-ray diffraction (XRD). To investigate, on a microscopic scale, the mixing-effects the perturbed angular correlation (PAC) technique was applied using some 1012 implanted radioactive 111In ions. The different phases were identified in the PAC spectra by comparison with those taken for single-phase material of intermetallic Ni/Sb compounds and pure Ni and Sb. After the 111In implantation usually up to 50% of the probes are found with PAC-parameters typical for the single metallic layers. The rest of the probes showed a complex mixture of electric field gradients (EFG). During ion-beam mixing this fraction increased to 100%. In some experiments individual EFGs were resolved indicating the formation of crystalline NiSb and Ni5Sb2 intermetallic phases.

Oxidation of elemental antimony by substituted ortho-benzoquinones

Abstract: The oxidation of elemental antimony by the o-quinones Y4C6O2-o(Y = Cl or Br) in diethyl ether gives the unusual antimony(V) products Sb(O2C6Y4)2.5·nEt2O (Y = Cl, n= 1.5; Y = Br, n= 1). The same quinones, and 3,5-di-tert-butyl-1,2-benzoquinone, upon treatment with Sb +½X2(X = Br or I) in toluene, give the antimony(III) derivatives Sb(cat)X (cat = substituted catecholate anion). The oxidations are shown by electron spin resonance spectroscopy to proceed via the o-semiquinone intermediates. Adducts of Sb(cat)I with bidentate neutral donors have been prepared. The structure of Sb(dbc)I(bipy)(dbc = 3,5-di-tert-butylcatecholate, bipy = 2,2′-bipyridine) has been shown to be that of a pseudo-octahedral molecule with a stereochemically active lone pair of electrons. Crystal parameters for Sb(dbc)I(bipy)·0.5bipy: triclinic, space group P, a= 9.779(4), b= 18.554(7), c= 8.944(3)A, α= 100.94(3), β= 115.11(3), γ= 86.82(4)°, Z= 2 and R= 0.044 for 3307 unique reflections.

Process for the removal of impurity elements from solutions of valuable metals

Abstract: A process is disclosed for removing impurity elements, such as arsenic, and if necessary antimony, iron or bismuth, from valuable metal containing, such as copper containing, strongly mineral acid solutions by way of solvent extraction with organic solutions of hydroxamic acids, and for selectively stripping the impurity elements therefrom. Antimony, iron or bismuth are stripped with complexing acids, and arsenic is stripped with an aqueous solution containing valuable metal ions at a pH value in the 1.5 to 5 range, a higher pH than the original valuable metal containing aqueous acid solution.

Dermatitis in workers exposed to antimony in a melting process.

Abstract: An employee at a brazing rod manufacturing plant developed a generalized eruption of follicular papules and pustules. His job tasks included breaking up antimony ingots and melting the pieces in a crucible; he was exposed to antimony metal dust and to antimony trioxide fumes. Two fellow employees who later performed the same job tasks developed similar eruptions. The clinical and workplace evaluations suggested that the fumes from melting antimony were the cause of the dermatoses, and that the current Occupational Safety and Health Administration permissible exposure limit is not adequate to prevent cutaneous effects of antimony exposure.

Antimony separation process

Abstract: An antimony recovery process is disclosed in which antimony-containing material is leached in a solvent including elemental sulfur and a caustic to preferentially leach antimony. The antimony-containing leach liquor from the leaching step is separated from the insoluble residue by filtration, and the antimony compounds in the separated leach liquor are crystallized to separate the antimony compounds from impurities which are left in solution in the leach liquor. The crystals are then redissolved and treated to create marketable antimony products of high purity, such as antimony metal, sodium hydroxy antimonate, sodium antimonate, antimony pentoxide, and antimony pentasulfide. Alternatively, the crystallized antimony compounds comprising primarily sodium thioantimonate crystals may be recovered and sold without further treatment. Waste products may be treated with soluble iron compounds and lime to render the waste products safe for disposal. Additionally, feed material having a high weight ratio of soluble arsenic to soluble antimony may be pretreated, if desired, to improve the purity of the recovered antimony products and to remove the arsenic for further treatment or disposal.

Texture improvement in high-permeability nonoriented electrical steel by antimony addition

Abstract: The mechanism of the significant effect of antimony additions on texture improvement was studied, and the results are as follows. When grain size before cold rolling was small, the antimony addition retarded {111} texture formation in the grain growth stage. When grain size before rolling was large, the {110} component increased in the early stage of recrystallization in the antimony-containing specimens because of the dense formation of deformation bands. Based on these effects of antimony additions on preferential texture formation, high-permeability nonoriented electrical steel has been produced at Kawasaki Steel Corporation.

Adsorption of antimony on Au(111) at room temperature

Abstract: This paper describes the growth of the film formed by the evaporation of antimony on to a Au(111) surface at room temperature. It has been studied using Auger electron spectroscopy, electron energy‐loss spectroscopy, low‐energy electron diffraction, and work function measurements. The first layer forms a (2√3×2√3)R30° structure, probably with AuSb2 stoichiometry. Subsequent layers are of pure Sb, with a layer‐by‐layer growth mode, and are disordered. The atomic density of Sb is approximately the same in the first layer and the subsequent Sb layers, and close to that for pure Sb. This work is compared to the formation of bimetallic layers of Pb, Bi, and Sn on Au(111). Also presented is a method for determining changes in the transmission probability of an Auger electron as it passes from one layer to the next.