Showing papers on "Bismuth published in 1996"
TL;DR: In this paper, the structural properties, thermal expansion, electrical conductivity, thermodynamic stability, and surface properties of bismuth oxide and solid solutions with face centred cubic, rhombohedral, tetragonal or layer structures are reviewed.
554 citations
TL;DR: In this paper, the authors analyzed the literature data reported on the partial oxidation of propane to organic compounds (acrolein, acrylic acid and acrylonitrile) over mixed metal oxides, mainly magnesium vanadates, vanadia bismuth molybdates and vanadia antimony.
Abstract: The present review analyses the literature data reported on the partial oxidation of propane to organic compounds (acrolein, acrylic acid and acrylonitrile) over mixed metal oxides, mainly magnesium vanadates, vanadia bismuth molybdates and vanadia antimony. The data were compared to those reported on the partial oxidation of propylene over bismuth molybdate and antimony—tin multicomponent oxides and over cuprous simple oxide. For both reactions, we analyzed the involved reaction mechanisms, intermediate species, active phases and active sites. The role of water produced during the reaction and that of the Bronsted acid sites were shown to be important in the determination of the selectivity of the expected products. The main conclusion of our study is that a good mix of acid-base and redox properties of the oxide surface should permit a controlled orientation of the reaction towards selective products.
346 citations
TL;DR: The dielectric properties of polycrystalline bismuth-based pyrochlores of the general chemical form Bi2(B232+B435+)O7 and B3+B5+) O7 were investigated as a function of temperature and frequency as mentioned in this paper.
268 citations
TL;DR: In this article, the authors examined Ferroelectric properties, crystal structure and microstructures for various Sr/Bi/Ta atomic ratio strontium bismuth tantalate (SBT) films prepared by metalorganic decomposition at 700 and 800° C.
Abstract: Ferroelectric properties, crystal structure and microstructures were examined for various Sr/Bi/Ta atomic ratio strontium bismuth tantalate (SBT) films prepared by metalorganic decomposition at 700 and 800° C. The 20% Sr-deficient and 10% Bi-excess (0.8/2.2/2) composition showed maximum remanent polarization (P r) values for both 700 and 800° C crystallization temperatures. From TEM analysis, the P r dependence on composition variation around the stoichiometric 1/2/2 composition was related to grain size and volume of voids. The effect of postannealing after Pt top electrode fabrication was also studied. On the films prepared at 800° C, postannealing markedly reduced the capacitor shorting rate. This was attributed to recrystallization of the Pt top layer, based on SEM analysis of the Pt layer and the Pt/SBT interface.
190 citations
TL;DR: The electrical anisotropy of layer-structured bismuth titanate (Bi 4 Ti 3 O 12 ) has been investigated by measurements of Seebeck coefficient, dielectric permittivity, DC conductivity, and complex impedance on single and polycrystalline samples as mentioned in this paper.
182 citations
TL;DR: The stringer zones and commonly the interaction zone at the base of the massive sulphide mounds in the Iberian Pyrite Belt contain bismuth and cobalt minerals that are not found in the overlying massive sulphides.
Abstract: The stringer zones and commonly the interaction zone at the base of the massive sulphide mounds in the Iberian Pyrite Belt contain bismuth and cobalt minerals that are not found in the overlying massive sulphides. These are fairly rare cobalt sulphoarsenides (cobaltite, alloclasite, galucodot) that were formed at the beginning of the massive sulphide genesis, and fairly common bismuth sulphides (bismuthinite, hammarite, wittichenite, cosalite, kobellite, joseite, etc.), including species rare at world scale (nuffieldite, giessenite, jaskolskiite) that were deposited from last stage high-temperature (> 300 °C) copper-bearing fluids containing Bi (Te, Se). The last stage fluids precipitated chalcopyrite containing Cu, Bi, Te, (Se) sulphosalts at the base of the sulphide mound to form a high cupriferous zone. Their interaction with the massive sulphides is reflected by the formation of an exchange zone, a few metres thick, showing chalcopyrite disease textures, at the base of the mound; this zone forms the upper limit of potentially economic copper enrichment and of bismuth minerals. Gold is undoubtedly in part, if not totally, related to this last phase. The bismuth concentrations being equivalent in the massive sulphides and the stringers, the presence of bismuth minerals in the stringer zones results from high-temperature conditions combined with a rarity of galena, which impedes absorption of available Bi. The distribution of these bismuth minerals provides a basic mineralogical zoning in the stringer zone, with a deep, low-aS2 zone containing native bismuth and tellurides and a shallow, higher-aS2 zone in contact with the massive ore sensu stricto and containing complex bismuth sulphides. These results make it possible to distinguish between sulphide veinlets belonging to stockwork zones of massive orebodies and veinlets of an ambiguous nature, and provide mineralogical criteria for the proximity of copper-rich zones. They enrich the very complex mineralogy of the Iberian Pyrite Belt.
114 citations
09 Jul 1996
TL;DR: In this article, the discovery and progress in Bi-based oxide high Tc superconductors are discussed. But the main focus of this paper is the development and progress of Bi-base oxides.
Abstract: Overview: discovery and progress in Bi-based oxide high Tc superconductors. Physics and chemistry: crystal structure thermal and magnetic properties tunnelling phases and their relationships in the Bi-Pb-Sr-Ca-Cu-O System phase equilibria and crystal chemistry of the high-temperature superconducting compounds of the system Bi2O3-SrO-CaO-CuO intrinsic pinning radiation effects preparation of precursor powders preparation of single crystals diffusion reaction in Bi-base oxides. Bulk, wire/tape and applications: Bi-based superconductor fabricated by the floating zone method Bi-based bulk current leads and their applications power-in-tube Bi2223 Ag-sheathed tape: basic process, microstructure and critical current density thermodynamics, microstructure and critical current density in Bi, Pb(2223) tapes manufacture and properties of Bi-2212-based Ag sheathed wires Bi-2212 Ag sheathed wire properties of Bi-2212 silver-sheathed tape and its application to magnets Bi-2212/Ag composite tapes processed by Doctor Blade or dip-coating process coils, power leads, busbars and cables fabrication and characterization of HYSC coils made from Bi-2223 conductors. Thin films and applications: MOCVD growth of high-quality B12223 superconducting films layer-by-layer growth of Bi-based superlattices by molecular beam epitaxy basic properties for BSCCO devices. Outlook: future prospects. (Part contents.)
98 citations
TL;DR: In this article, carbon-supported bismuth-palladium catalysts for the selective oxidation of glucose to gluconic acid, and the understanding of the promoting role played by Bi in these catalysts were investigated.
Abstract: This work is devoted to the preparation of carbon-supported bismuth-palladium catalysts for the selective oxidation of glucose to gluconic acid, and to the understanding of the promoting role played by Bi in these catalysts. Catalysts were prepared according to various experimental procedures from two kinds of precursors, containing either classical inorganic ligands (chloride, nitrate) or organic ligands of the carboxylate-type: the acetates and derivatives of the pyrazine-2,3-dicarboxylic acid. Depending on the precursors used, the catalytic performances were found to be very different; catalysts prepared by deposition of acetate-type precursors display the highest activity. The incorporation of bismuth in the Pd/C catalysts was confirmed to increase drastically the catalytic activity. The catalysts were characterized before and after their use in the catalytic operation by XRD, XPS, BET and IR. Depending on the preparation procedure used, the presence of BiOCl, Bi2O3 and several Bi-Pd alloys in the bimetallic catalysts after the activation step was deduced from XRD studies. Partial dissolution of bismuth during the catalytic tests was demonstrated by atomic absorption analysis of the reaction medium and elaborate investigations were undertaken to understand the individual effects of the various constituents of the reaction mixture on the dissolution process. Monometallic Bi/C catalysts were found to lose significantly larger amounts of bismuth than bimetallic Pd-Bi/C catalysts. Both glucose and gluconate appear as responsible for the dissolution of the promoting element. Notwithstanding the increase in the conversion rate observed when two monometallic Pd/C and Bi/C catalysts were used simultaneously, it was shown that the promoting role of bismuth was not merely dictated by the presence of bismuth in solution.
96 citations
TL;DR: In this article, a phase transition from the tetragonal structure of zirconia to the monoclinic phase takes place above 800 degrees c. The grain size dependence upon the annealing temperature has been evaluated using the Scherrer equation.
Abstract: Low-temperature (400-800{degrees}C) stabilization of tetragonal zirconia, prepared by a hydroxide gel route and low-temperature annealing, has been achieved by partial substitution of Zr{sup 4+} with Bi{sup 3+}. XRD and Raman spectroscopy have been used for characterization of the doped zirconia powders as well as for identification of the crystal symmetry. XPS data provide evidence of the presence of Bi(III) and of a small amount of a lower Bi sub-oxide. A phase transition from the tetragonal structure of zirconia to the monoclinic phase takes place above 800{degrees}C. The grain size dependence upon the annealing temperature has been evaluated using the Scherrer equation. Particle morphology and size have been directly imaged with the aid of SEM. 62 refs., 6 figs., 2 tabs.
88 citations
TL;DR: It is found that pressure strongly reduces the surface-induced excess hole concentration, clearly revealing a finite electron concentration at high pressures.
Abstract: We report an investigation of the low-temperature electrical transport properties of bismuth films under applied hydrostatic pressure. Films with their trigonal axis perpendicular to the film plane and thicknesses of 30, 50, and 500 nm were grown by molecular-beam epitaxy on BaF_2 substrates. At 500 nm thickness the behavior resembles that of bulk Bi. From the observed Shubnikov–de Haas oscillations we find a pressure-induced decrease in extremal Fermi cross section. For the 30-nm film, we obtain the low-temperature carrier densities for electrons and holes together with the corresponding mobilities from magnetoconductance data at pressures up to 20 kbar. We find that pressure strongly reduces the surface-induced excess hole concentration, clearly revealing a finite electron concentration at high pressures. We discuss our results within the context of a possible semimetal-semiconductor transition in thin Bi films.
84 citations
TL;DR: Bismuth preparations are commonly used to treat a variety of gastrointestinal disorders, including peptic ulcers and dyspepsia, and the safety profile of currently approved bismUTH preparations is excellent.
Abstract: Bismuth preparations are commonly used to treat a variety of gastrointestinal disorders, including peptic ulcers and dyspepsia. The safety profile of currently approved bismuth preparations, such as tripotassium dicitrato bismuthate (De-Nol), bismuth subsalicylate (Pepto-Bismol) and ranitidine bismuth citrate (Pylorid, Tritec), is excellent. Adverse reactions to these agents are mild, transient and infrequent, and reports of serious adverse reactions are rare. This, in part, reflects the low systemic bioavailability of bismuth from these medicines: less than 1% of the bismuth dose administered is absorbed. During repeated dosing with ranitidine bismuth citrate 200, 400 or 800 mg b.d. trough plasma bismuth concentrations remain well below 50 micrograms/L. After 4 weeks of treatment median concentrations of 3.4 micrograms/L or less were reported amongst 1210 duodenal ulcer patients receiving this new chemical entity, while mean concentrations of 5.1 micrograms/L (plasma) and 12.3 micrograms/L (blood) have been reported in two studies of patients receiving tripotassium dicitrato bismuthate 120 mg q.d.s. for 4 weeks. Transient peak plasma bismuth concentrations greater than 50 micrograms/L are observed 30-60 min after dosing with tripotassium dicitrato bismuthate in some patients, but are not associated with any toxic effects. After discontinuation of treatment with bismuth preparations its excretion in urine may continue for up to 3 months, by which time blood bismuth concentrations have declined to pretreatment values.
TL;DR: In this paper, the utilization of bismuth compounds in oxidation reactions of organic derivatives was discussed and both the pentavalent and trivalent states of Bismuth were found to display oxidizing power.
TL;DR: In this paper, the radiolytic reduction of aqueous solutions of bismuth perchlorate, the size and shape of the particles depending on the nature of the stabilizer was investigated.
Abstract: Nanometer-sized particles of bismuth are formed by the radiolytic reduction of aqueous solutions of bismuth perchlorate, the size and shape of the particles depending on the nature of the stabilizer. Well-facetted particle shapes (mean diameter: 20 nm) are observed with 2 × 10-4 M polyethyleneimine or 1 × 10-3 M polyacrylamide-10 (10% carboxyl groups) as stabilizer, whereas particles of less regular shape (mean diameter: 8 nm) are obtained with 1 × 10-3 M polyacrylamide-70 (70% carboxyl groups). The reduction of Bi(III) by 1-hydroxy ethyl methyl radicals, (CH3)2COH, is accompanied by H2 production, the bismuth particles formed serving as a catalyst. The absorption spectrum of colloidal bismuth has a weak maximum at 253 nm, which is not rendered by the spectrum calculated from the (rather scarce) dielectric data of Bi. Radiolysis experiments for the preparation of composite metal particles are also reported. The reduction of Cd2+ ions by organic radicals is catalyzed by Bi particles and leads to a cadmiu...
TL;DR: In this paper, the activity coefficients of neodymium and neptunium were estimated as 10−12.85 and 10−7.43 respectively from the standard potentials in LiCl-KCl eutectic molten salt and the distribution coefficients in the LiClKCl/bismuth system.
TL;DR: In this article, the authors improved the methods of preparation for Bi8(AlCl4)2 and Bi6Cl7 and the single crystal structures for these cluster compounds were re-investigated and reinterpreted.
Abstract: The methods of preparation for Bi8(AlCl4)2 and Bi6Cl7 have been improved and the single crystal structures for these cluster compounds re-investigated and re-interpreted. In addition, conductivity measurements and band structure calculations using the tight-binding approximation have been performed on Bi6Cl7 and related subvalent bismuth halides. – Bi8(AlCl4)2 consists of isolated AlCl4- anions and rather undistored square-antiprismatic Bi82+ clusters with an average Bi–Bi distance of 3.10 A. Relatively short intercluster Bi–Bi contacts of 3.90 A suggest weak bonding interactions between the Bi82+ units. In contrast, the structure determination of Bi6Cl7 implies that this structure should be regarded as being composed of discrete Bi95+ clusters and a polymeric BiIII–Cl anionic lattice including infinite, distorted α1[Bi2Cl24+] chains. According to the experimental and theoretical results, the Bi6X7 (X = Cl, Br) family of subvalent bismuth halide compounds are anisotropic semiconductors along the crystallographic c axis. The conductivity is mediated by the onedimensional α1[Bi2Cl24+] chains. These are interconnected with the Bi95+ clusters, which are acting as electron reservoirs. The related BiX (X = Br, I) family of subvalent bismuth halides are shown to be anisotropic semiconductors in the crystallographic b direction.
TL;DR: In this paper, high-axis oriented Bi 4 Ti 3 O 12 thin films have successfully been prepared on fused quartz substrates by sol-gel processing and the orientation degree of the thin film was about 87%.
21 Mar 1996-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this paper, single crystals of bismuth silicate were grown by the Bridgman method and the light output was 20% of BGO, giving FWHM energy resolution of 31% for 662 keV γ-rays ( 137 Cs).
Abstract: Single crystals of bismuth silicate were grown by the Bridgman method. The excitation and emission spectra are similar to BGO. The light output is 20% of BGO, giving FWHM energy resolution of 31% for 662 keV γ-rays ( 137 Cs). The decay constants are 2.4 ns (for 6% of intensity), 26 ns (12%) and 99 ns (82%). The radiation hardness against 60 Co γ-rays was about 10 5 –10 6 rad at the emission peak of 480 nm. Spontaneous recovery as well as optical annealing was also studied. BSO may be one the promising scintillators for high energy physics experiments.
TL;DR: In this article, a series of conventional and model bismuth-metal oxide catalysts (vanadates, molybdates, tungstates, and niobates) werephysically and chemically characterzied (Raman spectroscopy,BET, XPS, and methanol oxidation) to obtain additional insightsinto the structure-reactivity relationships of such catalyticmaterials.
TL;DR: In this article, the properties and characterization of thin film capacitors for ferroelectric random access memory (FERAM) applications were reported, and the films were prepared by spin-coating from carboxylate precursors.
Abstract: We report on the properties and characterization of SrBi 2 Ta 2 O 9 (SBT, or Y − 1) thin film capacitors for ferroelectric random access memory (FERAM) applications. The films were prepared by spin-coating from carboxylate precursors. The remanent polarization ( P r ) was 5−6 μ C/cm 2 and the coercive field was ∼55 kV/cm. Excellent fatigue endurance was observed up to 10 11 cycles. Auger analysis indicates bismuth diffusion through the Pt electrode after capacitor anneal which might require excess Bi in the precursor solution for stoichiometry control. No detectable amount of α emission was found from SBT films, which reduces the possibility of soft error when used in the memory devices.
Patent•
05 Apr 1996
TL;DR: In this paper, a glass composition capable of firing at ≤650°C and usable for bonding, sealing, covering or the like free from the fear of causing environmental problems or lowering electrical insulating property since PbO is not contained.
Abstract: PROBLEM TO BE SOLVED: To provided a glass composition capable of firing at ≤650°C and usable for bonding, sealing, covering or the like free from the fear of causing environmental problems or lowering electrical insulating property since PbO is not contained. SOLUTION: This bismuth based glass has a composition contg., by weight, of 20-80% Bi 2 O 3 , 5-35% B 2 O 3 , 0-35% BaO, 0-30% SrO, 5-40% BaO+SrO, 0-9% ZnO, 0-10% CaO, 0-5% Fe 2 O 3 , 0-10% CuO, 0.1-20% ZnO+CaO+Fe 2 O 3 +CuO, 0-8% SiO 2 , 0-5% Al 2 O 3 , 0-5% Cs 2 O and 0-5% F 2 and contains substantially no PbO, and a refractory filler is added, at need. COPYRIGHT: (C)1997,JPO
TL;DR: It is believed that the significantly greater solubility of RBC, especially at lower pH values, is highly relevant to its better antipepsin and anti‐H.
Abstract: BACKGROUND: Ranitidine bismuth citrate (RBC) is a new chemical entity for the treatment of peptic ulcer disease. RESULTS: RBC is freely soluble in water (more than 600 mg/mL at pH 4.6), whereas an equimolar admixture of its component molecules, bismuth citrate and ranitidine, formed an almost totally insoluble suspension. Even at very low pH values (around 2.0), the solubility of bismuth in ranitidine bismuth citrate was at least two-fold better than in the admixture. Comparison of several physico-chemical characteristics indicated that RBC possessed significantly different melting point properties, X-ray powder diffraction patterns, infra-red spectra and 13C-NMR solid-state spectra to the admixture. Ranitidine bismuth citrate inhibited human pepsin isoenzymes 1, 2, 3 and 5 but the admixture was inactive. RBC showed approximately two-fold greater anti-Helicobacter pylori activity in vitro than the admixture (geometric mean minimum inhibitory concentrations of 12.5 and 25.7 mg/L, respectively) and was more rapidly bactericidal. In a mouse model of gastric H. pylori colonization, 200 mg/kg of bismuth, given as RBC, eradicated the organism from all mice while only 10% of infections were eradicated by equivalent levels of bismuth in admixture form. CONCLUSION: It is believed that the significantly greater solubility of RBC, especially at lower pH values, is highly relevant to its better antipepsin and anti-H. pylori action compared to the insoluble admixture of bismuth citrate and ranitidine.
TL;DR: In this article, photoelectron spectra of antimony Sb−N=2-9 and of bismuth clusters Bi−N =2−9 with a photon energy of 4.03 eV were recorded.
Abstract: We recorded photoelectron spectra of antimony Sb−N=2–9 and of bismuth clusters Bi−N=2–9 with a photon energy of 4.03 eV, as well as of Bi−N=2–21 with a photon energy of 5.0 eV. The experimentally determined photoelectron thresholds and peak positions of Sb−N=2–5 and Bi−N=2–5 are compared with the results of ab initio density‐functional (LCAO) calculations. The agreement between the experimental thresholds and the calculated adiabatic electron affinities, as well as between the first maxima in the spectra and the calculated vertical detachment energies is fair to good for the antimony clusters and qualitative for the bismuth systems. For the calculation of the ionization (detachment) energies we determined for the neutral and anionic clusters the most stable structures by LCAO calculations. In particular, the tetramer cluster anions have a ‘‘roof’’ structure, while the negatively charged pentamers are planar rings [with similarities to the (C5H5)− anion]; positive and negative trimers are nonlinear. Furthe...
TL;DR: In this article, bismuth-substituted nickel-zinc ferrites have been synthesized by a solution route in the composition range Ni 0.5 Zn 0.4 Bi x Fe 2.0− x O 4, with 0 ≤ x ≤ 0.2.
TL;DR: In this article, the effects of bismuth, lead, and tungsten on the cobalt-catalyzed synthesis of single-layer carbon nanotubes and nanoparticles have been studied.
TL;DR: In this article, the electrochromic properties of the reversible electrodeposition of metallic bismuth onto transparent conducting substrates were studied with interest in the electro chromic phenomena produced by plating and stripping a thin metallic film.
TL;DR: In this paper, the effect of bismuth layers on hydrogen and oxygen adsorption in ultra-high vacuum (UHV), and the electro-oxidation of CO in dilute sulphuric acid electrolyte was investigated.
TL;DR: In this article, the x-ray reflectivity as a function of angle of incidence was measured for bismuth-gallium mixture and the predicted stratification of the density distribution along the normal to the interface and the segregation of the excess surface concentration of Bi into a monolayer atop the bulk mixture.
Abstract: The density distribution normal to the liquid–vapor interface of a bismuth–gallium mixture (0.18% Bi and 99.82% Ga) has been studied by measurement of the x‐ray reflectivity as a function of angle of incidence. The data obtained confirm the predicted stratification of the density distribution along the normal to the interface and the segregation of the excess surface concentration of Bi into a monolayer atop the bulk mixture.
TL;DR: Bismuth oxide is an interesting dielectric material with potential applications for optical coatings, MIS capacitors, and microwave integrated circuits as discussed by the authors, which has a number of advantages over other deposition techniques, e.g., precise control of oxyg
Abstract: Bismuth oxide is an interesting dielectric material with potential applications for optical coatings, MIS capacitors, and microwave integrated circuits. CVD growth has a number of advantages over other deposition techniques, e.g., precise control of oxyg
TL;DR: Quantitative chemical analyses have been performed for the isoelectronic, trigonal pyramidal closo-clusters Sn (5)(2-), Sb(5)(3+), Tl( 5)(7-), Pb(4)(-), and Bi(5+), both with extended Hückel (eH) and Hartree-Fock (HF) methods and the results agree well with available experimental data.
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....
Patent•
31 May 1996TL;DR: In this article, a bismuth-based layered ferroelectric oxide thin film is formed on the conductive oxide and a further conductive layer is formed in the buffer layer.
Abstract: A ferroelectric memory includes a silicon substrate having a buffer layer on the substrate and a conductive oxide thin film on the buffer layer. A bismuth based layered ferroelectric oxide thin film is formed on the conductive oxide and a further conductive layer is formed on the ferroelectric layer. In one embodiment, the buffer layer is substantially lattice matched with the silicon substrate, the conductive oxide thin film is substantially lattice matched with the buffer layer, and the bismuth-based layered ferroelectric oxide thin film is substantially lattice matched with the conductive oxide thin film. Additionally, the invention includes the use of a superlattice structure for the ferroelectric layer.