Showing papers on "Antimony published in 2006"

Sorption of Sb(III) and Sb(V) to goethite: influence on Sb(III) oxidation and mobilization.

Abstract: Antimony is an element of growing interest for a variety of industrial applications, even though Sb compounds are classified as priority pollutants by the Environmental Protection Agency of the United States. Iron (Fe) hydroxides appear to be important sorbents for Sb in soils and sediments, but mineral surfaces can also catalyze oxidation processes and may thus mobilize Sb. The aim of this study was to investigate whether goethite immobilizes Sb by sorption or whether Sb(III) adsorbed on goethite is oxidized and then released. The sorption of both Sb(III) and Sb(V) on goethite was studied in 0.01 and 0.1 M KClO4 M solutions as a function of pH and Sb concentration. To monitor oxidation processes Sb species were measured in solution and in the solid phase. The results show that both Sb(III) and Sb(V) form inner-sphere surface complexes at the goethite surface. Antimony(III) strongly adsorbs on goethite over a wide pH range (3-12), whereas maximum Sb(V) adsorption is found below pH 7. At higher ionic strength, the desorption of Sb(V) is shifted to lower pH values, most likely due to the formation of ion pairs KSb(OH)6 degrees. The sorption data of Sb(V) can be fitted by the modified triple-layer surface complexation model. Within 7 days, Sb(III) adsorbed on goethite is partly oxidized at pH 3, 5.9 and 9.7. The weak pH-dependence of the rate coefficients suggests that adsorbed Sb(III) is oxidized by 02 and that the coordination of Sb(III) to the surface increases the electron density of the Sb atom, which enhances the oxidation process. At pH values below pH 7, the oxidation of Sb(III) did not mobilize Sb within 35 days, while 30% of adsorbed Sb(III) was released into the solution at pH 9.9 within the same time. The adsorption of Sb(III) on Fe hydroxides over a wide pH range may be a major pathway for the oxidation and release of Sb(V).

Perovskite (Na0.5K0.5)1−x(LiSb)xNb1−xO3 lead-free piezoceramics

Abstract: Lead-free potassium sodium niobate piezoelectric ceramics substituted with lithium and antimony (Na0.5K0.5)1−x(LiSb)xNb1−xO3 have been synthesized by conventional solid state sintering method. Compositionally engineered around the orthorhombic-tetragonal polymorphic phase transition, the dielectric and piezoelectric properties were further enhanced with the addition of lithium and antimony substituted into the perovskite structure. The combined effects of lithium and antimony additions resulted in a downward shift in the orthorhombic-tetragonal (TO-T) without significantly reducing TC. The dielectric, piezoelectric, and electromechanical properties were found to be e∕e0>1300, d33>260pC∕N, and kp>50%, while maintaining low dielectric loss. The enhanced polarizability associated with the polymorphic TO-T transition and high TC transition (∼390°C) should provide a wide range of temperature operation.

Comparison of antimony behavior with that of arsenic under various soil redox conditions.

Abstract: The oxidation states and host phases of Sb and As in soil samples of mine tailing (Ichinokawa mine, Ehime, Japan) and in laboratory soil-water systems were determined by X-ray absorption fine structure (XAFS) spectroscopy. HPLC-ICP-MS was used for speciation of Sb and As in soil water. In the Ichinokawa soil water system, Sb was present exclusively as the oxidized form, Sb(V), over a wide redox range (from Eh = 360 to -140 mV, pH 8), while As was present as a mixture of As(III) and As(V). This finding was confirmed in the laboratory experiments. These results suggest that Sb(V) is a very stable form in the environment and that Sb is oxidized at more negative Eh than As. Combining the results of Fe and Mn XAFS analyses and a positive correlation among Sb, As, and Fe abundances in the soil, the host phases of Sb and As in soil were Fe(III) hydroxide. XAFS analyses of Sb and As are also consistent with this finding. Under reducing conditions, the concentration of As in the soil water increased whereas that of Sb decreased in both the Ichinokawa and laboratory systems. This suggests that this contrasting behavior is controlled mainly by the different redox properties of Sb and As.

A simple solution route to single-crystalline Sb2O3 nanowires with rectangular cross sections.

Abstract: We report a simple solution route to large-scale synthesis of uniform, single-crystalline, and well-faceted orthorhombic antimony trioxide (Sb(2)O(3)) nanowires with rectangular cross sections by direct air oxidation of bulk metal antimony (Sb) in a mixed solution made of ethylenediamine (EDA) and deionized water (DIW). The as-synthesized products were analyzed by range of methods, such as XRD, SEM, EDX, TEM, SAED, HRTEM, FTIR, Raman, UV-vis absorption, and photoluminescence (PL) spectra. The as-synthesized Sb(2)O(3) nanowires with rectangular cross sections are usually hundreds of micrometers in length, typically 80-100 nm in width, and 60-80 nm in thickness. The novel room temperature photoluminescence properties of Sb(2)O(3) nanowires with rectangular cross sections displayed a significant UV luminescence with a strong emission band at 374 nm, which was reported for the first time, indicating the as-synthesized products with an optical band gap E(g) = 3.3 eV. It is expected that as-synthesized Sb(2)O(3) nanowires would be a new member of functional materials and used in the manufacture of advanced nanodevices.

Solar cell using low iron high transmission glass with antimony and corresponding method

Abstract: A high transmission and low iron glass is provided for use in a solar cell. The glass substrate may be patterned on at least one surface thereof. Antimony (Sb) is used in the glass to improve stability of the solar performance of the glass upon exposure to ultraviolet (UV) radiation and/or sunlight. The combination of low iron content, antimony, and/or the patterning of the glass substrate results in a substrate with high visible transmission and excellent light refracting characteristics.

Synthesis, structure and properties of doped Bi2O3

Abstract: Oxide ion conductors have been increasingly studied for many years because of their application in devices with high economical interest such as solid oxide fuel cells (SOFC), oxygen sensors, dense ceramic membranes for oxygen separation, and membrane reactors for oxidative catalysis. Bismuth oxides present polymorph forms, such as δ-, β- or γ-Bi 2 O 3 , with great potential for such applications, alone or in combination with other oxides. The present study investigates the influence of selected ions (Fe 3+ , Sb 3+ /Sb 5+ , and Ta 5+ ), introduced as dopant in α-Bi 2 O 3 and their effect on the structure and properties of the oxide polymorph forms obtained at high temperature. The molar ratio was Bi 2 O 3 :M x O y 0.95:0.05 where M = Fe 2 O 3 , Sb 2 O 3 or Ta 2 O 5 , respectively. The structural changes of α-Bi 2 O 3 were analysed by powder X-ray diffraction, SEM/EDX analysis and infrared spectroscopy. The structural changes are correlated with bulk ceramic characteristics (density, porosity) and their electrical behaviour versus temperature. The presence of some dopants (antimony and tantalum) on bismuth sites enlarges and enhances the stability of the polymorph forms, which is relevant to potential application.

Electrical activation and electron spin coherence of ultralow dose antimony implants in silicon

Abstract: We implanted ultralow doses (2×1011cm−2) of antimony ions (Sb121) into isotopically enriched silicon (Si28) and find high degrees of electrical activation and low levels of dopant diffusion after rapid thermal annealing. Pulsed electron spin resonance shows that spin echo decay is sensitive to the dopant depths, and the interface quality. At 5.2K, a spin decoherence time, T2, of 0.3ms is found for profiles peaking 50nm below a Si∕SiO2 interface, increasing to 0.75ms when the surface is passivated with hydrogen. These measurements provide benchmark data for the development of devices in which quantum information is encoded in donor electron spins.

Glazing panel having solar screening properties

Abstract: A glazing panel having beneficial anti-solar properties comprises a vitreous substrate carrying a tin/antimony oxide coating layer containing tin and antimony in a Sb/Sn molar ratio of from 0.01 to 0.14. In one application the coated substrate has a solar factor FS of less than 70% and the panel is formed by chemical vapor deposition from a reactant mixture comprising a source of tin and a source of antimony. In another application it is particularly suitable for use in vehicle glazing, in particular in vehicle roof windows, and the coated substrate has a spray-formed pyrolytic tin/antimony oxide coating having a thickness of at least 400 nm and, whereby the coated substrate has a luminous transmittance (TL) of less than 35% and a selectivity (TL/TE) of at least 1.3.

Biogeochemistry of arsenic and antimony in the North Pacific Ocean

Abstract: The biogeochemical cycles of the metalloid elements arsenic and antimony were examined along a 15,000 km surface water transect and at 9 vertical profile stations in the western North Pacific Ocean as part of the 2002 IOC Contaminant Baseline Survey. Results show that the speciation of dissolved arsenic (As III, As V, and methylated As) was subtly controlled by the arsenate (AsV)/phosphate ratio. An additional fraction of presumed organic arsenic previously reported in coastal waters was also present (∼15% of the total As) in oceanic surface waters. Dissolved inorganic antimony displayed mildly scavenged behavior that was confirmed by correlations with aluminum, but atmospheric inputs that may be anthropogenic in origin also affected its concentrations. Monomethyl antimony, the predominant organic form of the element, behaved almost conservatively throughout the water column, radically changing the known biogeochemical cycle of antimony.

Laser surface annealing of antimony doped amorphized semiconductor region

Abstract: A sheet resistance stabilized recrystallized antimony doped region may be formed within a semiconductor substrate by annealing a corresponding antimony doped amorphized region at a temperature from about 1050° C. to about 1400° C. for a time period from about 0.1 to about 10 milliseconds. Preferably, a laser surface treatment is used. The laser surface treatment preferably uses a solid phase epitaxy. In addition, the antimony doped region may be co-doped with at least one of a phosphorus dopant and an arsenic dopant. The antimony dopant and the laser surface treatment lend sheet resistance stability that is otherwise absent when forming solely phosphorus and/or arsenic doped regions.

Crystallization Behavior and Physical Properties of Sb-Excess Ge2Sb2 + x Te5 Thin Films for Phase Change Memory (PCM) Devices

Abstract: The crystallization behavior of antimony(Sb)-excess Ge 2 Sb 2+x Te 5 was examined. Sb-excess GST showed crystallization (T c ) and melting (T M ) temperatures of 205 and 550°C, respectively, slightly higher T C and lower T M values than stoichiometric Ge 2 Sb 2 Te 5 compounds. It also showed a substantially different crystallization behavior compared to the stoichiometric Ge 2 Sb 2 Te 5 composition. The resulting Sb-excess GeSbTe thin film showed a grain growth dominated crystallization behavior.

The role of antimony on properties of widely varying GaInNAsSb compositions

Abstract: Antimony has been used as a surfactant to improve the quality of GaInNAs∕GaAs quantum wells for long-wavelength optoelectronics. We demonstrate the importance of antimony as a reactive surfactant and the proper usage of it with dilute nitrides in order to tailor the properties of solar cell and laser devices. The effects of the addition of antimony to low indium concentration (∼8%) and low strain GaInNAs material (for 1.0eV solar cell applications) were investigated. It was assumed previously that adding antimony helped all GaInNAs alloys, but the validity of this was not previously tested. The addition of antimony to high indium concentration (∼32%) and high strain GaInNAs samples led to a dramatic improvement in optical quality and a widening of the growth window, while it led to a degradation in the low indium (low strain) composition samples. The addition of indium under constant antimony flux also improved the optical quality of the GaInNAs material. Variations in the indium and antimony compositions...

Modification of Mg2Si Morphology in As-Cast Mg-Al-Si Alloys with Strontium and Antimony

Abstract: The effects of antimony (Sb) and strontium (Sr) additions on the microstructure of Mg-Al-Si alloys were studied. The results show that the additions of Sb and Sr can modify the Mg2Si particles from Chinese script shape to refined polygonal shape. Tensile strength and creep resistance are improved, and tensile elongation is also increased in the modified alloy. Sr modification is more effective than Sb modification of AS52 alloy for refining the microstructure and thus improving its properties.

Antimony and Antimony Compounds

Abstract: The article contains sections titled: 1. Introduction 2. Physical Properties 3. Chemical Properties 4. Occurrence 5. Beneficiation 6. Recovery of the Metal 6.1. Roasting 6.2. Reduction of Oxide to the Metal 6.3. Direct Reduction to the Metal 6.4. Hydrometallurgical and Electrolytic Methods 6.5. Recovery from Byproducts 7. Refining 8. Fine Purification 9. Recovery of Antimony Oxide 10. Antimony Alloys and Intermetallic Compounds 11. Antimony Compounds 11.1. Antimony Chlorides 11.2. Antimony Fluorides 11.3. Antimony Tribromide 11.4. Antimony Triiodide 11.5. Antimony Oxides 11.6. Antimonic Acid and Antimonates 11.7. Antimony Sulfides 11.8. Antimony Sulfate 11.9. Stibine 11.10. Organometallic Compounds 12. Chemical Analysis 13. Uses 14. Recycling 15. Economic Aspects 16. Toxicology The article describes the properties, production, and usage of the element antimony and its primary compounds. Stibnite, which is referred to as crude antimony when its Sb2S3 content is above 90 %, has a low melting point and it can be extracted by melting (liquidation). Antimony metal is recovered from ore primarily by pyrometallurgical techniques. Because rich ores are becoming rare, greater recourse is being taken to intermediates in processing and metal industries. Hydrometallurgical processing is suitable for some ores containing precious metals and is used by the Sunshine Mining Co. (USA). Refining and fine purification techniques are used for production of pure antimony metal. There is growing demand for extremely pure antimony. Antimony oxide is being used as flame retardant in increasing quantities. Antimony is a component of many lead and tin alloys, which are important materials for making bearings and solders. Preparation, properties, and usage of the antimony halides, oxides, sulfides, and other compounds, as well as organometallic compounds are described. Other important aspects are recycling, economics, and toxicology.

The nuclear electric quadrupole moment of antimony from the molecular method

Abstract: Relativistic Dirac-Coulomb (DC) Hartree-Fock calculations are employed to obtain the analytic electric field gradient (EFG) on the antimony nucleus in the SbN, SbP, SbF, and SbCl molecules. The electronic correlation contribution to the EFGs is included with the DC-CCSD(T) and DC-CCSD-T approaches, also in the four-component framework, using a finite-difference method. The total EFG results, along with the experimental nuclear quadrupole coupling constants from microwave spectroscopy, allow to derive the nuclear quadrupole moments of Sb121 and Sb123, respectively, as −543(11) and −692(14)mb.