Small Amount Of Bi Research Articles

Electrochemical Properties of Low Bi Doped La0.60Dy0.10Sr0.30Mn(1-x)BixO3 Perovskite Magneticaloric Materials

Developing low-cost, high-durability and high-performance electrocatalytic materials are needed for hydrogen/oxygen evolution (HER/OER) and oxygen reduction reactions (ORR) which are crucial steps for regenerative fuel cells. Although Pt-based, RuO2 and IrO2 materials are widely used for these purposes, other alternative materials are required with desired properties. In this regard, we studied the electrochemical properties of lanthanum-based perovskites which were synthesized by sol-gel method. We investigated the addition of 10% Dy and 30% Sr into the A site and a small amount of Bi (x: 0, 0.03 and 0.1) added into the B site of La0.60Dy0.10Sr0.30Mn(1-x)BixO3 perovskites on HER, OER and ORR in 1 M KOH alkaline media at room temperature. While the addition of 0% and 3% Bi exhibited poor HER activities, the effect of 10% Bi in the structure enhanced HER activities by lowering onset potential from -1.389 V to -1.036 V (vs. Ag/AgCl) and increasing specific current density at -1.4 V from -13.3 mA cm-2 to -121.8 mA cm-2. Similarly, OER activity was also improved due to 10% Bi and onset potential and specific current density was found to be 0.758 V and 88.3 mA cm-2, respectively. The large Tafel slopes indicate that the ORR mechanism is possible in the structure but at a slow rate. The addition of 10% Bi in the structure resulted in a very high resistance of 19.3 kΩ and it reduced to a desired value of 3.5 kΩ due to ion conducting paths developed in the catalysts.

Warm white-light emitting silica films prepared using lead-free double perovskite QDs.

Lead-free double perovskite has attracted widespread attention due to its good stability and non-toxicity. In this work, Cs2AgxNa1-xInCl6 quantum dots were synthesized via a thermal injection method using non-toxic precursors. Based on the wide spectrum of self-bound excitons, the quantum dots achieved white light emission. Bi-doped Cs2AgxNa1-xInCl6 quantum dots with excellent luminescence performance have the same cubic structure, and they have a larger Stokes shift. The cubic perovskite space group is Fm3[combining macron]m, and [NaCl6], [AgCl6] and [InCl6] octahedrons alternately appear in the cubic structure. The photoluminescence quantum yield of Cs2AgxNa1-xInCl6 is improved by doping with a small amount of Bi; the PL QY increased to 57.3% with an obvious emission peak at 600 nm. The stability and luminescence intensity of perovskite QDs were further enhanced by SiO2 coating and a Cs2AgxNa1-xInCl6:Bi-SiO2 thin film was prepared using perhydropolysilazane as the precursor. The materials have huge application potential in the field of white light emission and display.

A green method to prepare magnetically recyclable Bi/Bi25FeO40-C nanocomposites for photocatalytic hydrogen generation

In the present work, magnetically recyclable Bi/Bi25FeO40-C nanocomposites were synthesized through a one-step hydrothermal approach and then analyzed. The analysis results manifested that non-toxic and biodegradable sodium alginate takes a key role in successful preparation of Bi/Bi25FeO40-C. Sodium alginate can totally suppresses the formation of BiFeO3 because it changes the alkalinity of the medium, and at the same time Fe precursor greatly restrains the reduction of Bi3+ to Bi by sodium alginate, so the final product is Bi/Bi25FeO40 with a small amount of Bi instead of Bi, BiFeO3 or Bi/BiFeO3. Bi/Bi25FeO40-C showed enhanced photocatalytic activity in hydrogen generation as compared with pure Bi25FeO40 due to the surface plasmonic resonance effect of Bi and electron conductivity of carbon, which promote electron-hole separation and light absorption of the Bi/Bi25FeO40-C, resulting in high photocatalytic efficiency. The Bi/Bi25FeO40-C even exhibited higher catalytic efficiency than noble metallic nanoparticles and good reusability in p-nitrophenol reduction. This work provides a green way to prepare Bi/Bi25FeO40-C for catalytic reactions.

Novel Quaternary Dilute Magnetic Semiconductor (Ga,Mn)(Bi,As): Magnetic and Magneto-Transport Investigations

Magnetic and magneto-transport properties of thin layers of the (Ga,Mn)(Bi,As) quaternary dilute magnetic semiconductor grown by the low-temperature molecular-beam epitaxy technique on GaAs substrates have been investigated. Ferromagnetic Curie temperature and magneto-crystalline anisotropy of the layers have been examined by using magneto-optical Kerr effect magnetometry and low-temperature magneto-transport measurements. Post-growth annealing treatment of the layers has been shown to enhance the hole concentration and Curie temperature in the layers. A significant increase in the magnitude of magneto-transport effects caused by incorporation of a small amount of Bi into the (Ga,Mn)As layers, revealed in the planar Hall effect (PHE) measurements, is interpreted as a result of enhanced spin-orbit coupling in the (Ga,Mn)(Bi,As) layers. A two-state behaviour of the planar Hall resistance at zero magnetic field provides its usefulness for applications in non-volatile memory devices.

Surface Analysis of Magnesium-Based Intermetallic Compounds

Introduction Magnesium-based rechargeable battery is expected as a candidate of beyond lithium-ion battery1. Since the magnesium metal anode does not form dendrite during the deposition process, most of the studies for the magnesium battery are based upon the magnesium metal anode. Typically the electrochemical deposition/dissolution process of the magnesium metal has never been observed in conventional ionic electrolytes such as Mg(ClO4)2 or Mg(PF6)2. Recently it was reported that Mg(TFSI)2 in glyme-based solvents showed some reversibility in Mg deposition/dissolution2, 3. However the overpotential of the Mg deposition/dissolution process in the Mg(TFSI)2-based electrolyte solution is relatively high > 1.0 V. Thus it is still difficult to utilize magnesium metal as an anode active material for a rechargeable magnesium battery with a conventional ionic electrolyte. We have been working on magnesium-based intermetallic compounds as alternative anode active materials for magnesium batteries, because the intermetallic compounds are compatible with conventional ionic electrolytes4. Here we conducted electrochemical and surface analyses of Mg3Bi2 thin film electrodes in various electrolyte solutions to understand the electrochemical activity of the magnesium-based intermetallic compounds. Experimental The Mg3Bi2 thin film electrodes were fabricated co-sputtering process of magnesium and bismuth on copper substrate at 200 ºC. A three-electrode cell with Mg3Bi2 thin film working electrode was fabricated in an Ar filled glove box. A double junction Ag/Ag+ reference electrode and a platinum counter electrode were employed for the electrochemical measurement. Surface analyses were carried out using in situ FTIR based upon a diamond ATR optical system, and X-ray photoelectron spectroscopy (XPS). Results The obtained thin film electrode was characterized using XRD. A highly crystallined Mg3Bi2 thin film with small amount of Bi was obtained via the RF-sputtering without any post-annealing process. It suggests that the substrate temperature 200 ºC is high enough to form the Mg3Bi2 thin film. A cyclic voltammogram for the Mg3Bi2 thin film electrode in 0.5 M Mg(TFSI)2 BuMe-triglyme solution, is shown in Figure 1. Very clear cathodic and anodic currents were observed at -2.3 V vs. Ag/Ag+. The overpotential was approx. 100 mV while the magnesium deposition/dissolution process in the particular electrode shows extremely high overpotential approx. 2.0 V. Thus we think the Mg3Bi2 intermetallic compound has clear advantage against the magnesium metal in terms of the energy efficiency. The XPS analysis results suggested that the TFSI anion was reduced at the surface of the Mg3Bi2 thin film electrode during the electrochemical measurement, however the amount of the decomposed products were much less than that on magnesium metal. Further discussion will be done in the session.

Phase Transition, Dielectric and Piezoelectric Properties of Lead-Free Piezoelectric (K1/2Na1/2)NbO3 – Bi(Zn2/3Nb1/3)O3 Ceramics

The lead–free piezoelectric ceramics on the binary system of (1-x)(K1/2Na1/2)NbO3–xBi(Zn2/3Nb1/3)O3 [(1-x)KNN–xBZnN]; x = 0.01–0.10 were fabricated by the solid state reaction method. The structure and phase transition were determined by X-ray diffraction.The results of XRD patterns suggested that Bi(Zn2/3Nb1/3)O3 completely diffuse into the (K1/2Na1/2)NbO3 lattices to form a solid solution. The crystal structure was in an orthorhombic phase for x ≤ 0.01. When reaching 0.01 < x ≤ 0.07, crystal structure became a rhombohedral phase and transformed to a pseudo-cubic structure for x > 0.07. The dielectric data shows that the amount of Bi(Zn2/3Nb1/3)O3 added in the (K1/2Na1/2)NbO3 decreases the ferroelectric – paraelectric transition temperature progressively. Furthermore, optimum piezoelectric and ferroelectric properties were observed at the composition, x = 0.01: effective piezoelectric coefficients (d33 *) = 498 pm/V, remanent polarization (Pr) = 23.3 µC/cm2, coercive field (Ec) = 14 kV/cm, maximum strain (Smax) = 0.3% and Curie temperature (TC) = 380°C. The results of this study show that KNN with a small amount of Bi(Zn2/3Nb1/3)O3 (x = 0.01) can be one of lead-free piezoelectric ceramic candidate.

Structure, piezoelectric and multiferroic properties of Bi(Ni0.5Mn0.5)O3-modified BiFeO3–BaTiO3 ceramics

(0.725 − x)BiFeO3–0.275BaTiO3−xBi(Ni0.5Mn0.5)O3 + 1 mol% MnO2 lead-free multiferroic ceramics have been fabricated by a conventional ceramic technique and the structure, multiferroic and piezoelectric properties of the ceramics have been investigated. All the ceramics sintered at 950 °C for 2 h possess a pure perovskite structure. XRD patterns show that a coexistence of rhombohedral and pseudocubic phases are formed at x = 0.05−0.07. The average grain size decreases and the range of the grain size distribution greatly becomes narrow after the addition of Bi(Ni0.5Mn0.5)O3. The dielectric peak becomes gradually diffusive with increasing x. A small amount of Bi(Ni0.5Mn0.5)O3 doping (x ≤ 0.02) maintain the ferroelectric (P r = 16.7−19.3 μC/cm2), piezoelectric properties (d 33 = 124−145 pC/N) and ME coefficient performance (α 33 = 444.45–553.65 mV cm−1 Oe−1).

Macroscopic and Nanoscopic Polarization Relaxation Kinetics in Lead‐Free Relaxors Bi1/2Na1/2TiO3–Bi1/2K1/2TiO3–BiZn1/2Ti1/2O3

The stability of the field‐induced ferroelectric (FE) state was studied in relaxor lead‐free ceramics (1 − y)[0.81Bi1/2Na1/2TiO3–0.19Bi1/2K1/2TiO3]–yBiZn1/2Ti1/2O3 both macroscopically and microscopically. A strong dc electric field results in the formation of a stable FE state with a large piezoelectric coefficient for compositions with a small amount of Bi(Zn1/2Ti1/2)O3, which are in the non‐ergodic relaxor state at room temperature. Increasing temperature promotes ergodic relaxor behavior, which is accompanied by the rapid destabilization of the induced state, that is, small relaxation times. Based on the obtained data, it is proposed that the depolarization is a two‐step process consisting of an initial realignment of the FE domains and their subsequent breakup into polar nanoregions. The ergodic relaxor behavior is also promoted by increasing the Bi(Zn1/2Ti1/2)O3 content. The related charge disorder results in an enhancement of random electric fields and consequently a stable FE state cannot be induced even at room temperature.

AES Studies of Saturation in Surfactant Segregation Process in Co/Cu Multilayers

The chemical composition of successive layers in a Co/Cu multilayered system was studied during growth with Auger electron spectroscopy. Experiments were carried out on a sample with 10 repetitions of Co(1 nm)/Cu(2 nm) evaporated at a very low deposition rate in ultrahigh vacuum. A very small amount of Bi or Pb (0.06 nm) was deposited on each Cu film in the system. The experimental data have shown that the concentration of Bi and Pb increases with the number of deposited trilayers up to coverage corresponding to 5 trilayers. At that point the concentration of the surfactant saturated. The changes in the surfactant concentrations are described with a simple model depicting the interaction of the surfactant atoms with the system and how the evolution of the segregation processes. It allows the prediction of the saturation concentration and helps to explain the behaviour of various elements used as a surfactant. The comparison between the theoretical predictions and the experimental results is also discussed.

Phase Transition Temperatures and Piezoelectric Properties of (Bi1/2Na1/2)TiO3-and (Bi1/2K1/2)TiO3-Based Bismuth Perovskite Lead-Free Ferroelectric Ceramics

The phase transition temperatures and the dielectric, ferroelectric, and piezoelectric properties of bismuth perovskite lead-free ferroelectric ceramics such as (Bi(1/2)Na(1/2))TiO3 (BNT)- and (Bi(1/2)Na(1/2))TiO3 (BKT)-based solid solutions have been reviewed. According to the results obtained by our group, these ceramics can be considered as superior lead-free piezoelectric materials for reducing environmental damage. Perovskite-type ceramics appear to be suitable for actuator and high-power applications that require a large piezoelectric constant d33 and a high Curie temperature TC or a high depolarization temperature Td (> 200 degrees C). In this paper, we summarize the relationship between phase transition temperatures and piezoelectric properties. In the case of the BNT-based solid solutions, the highest piezoelectric properties were obtained at the morphotropic phase boundary (MPB) between rhombohedral and tetragonal phases. However, d33 and Td were shown to have a tradeoff relationship. Considering the high Td and high d33, the tetragonal side of the MPB composition is suitable for piezoelectric actuator application. Meanwhile, the Qm values on the rhombohedral side of the MPB composition were better than those on the tetragonal side, and excellent high-power characteristics were obtained for Mn-doped BNT-(Bi(1/2)Na(1/2))TiO3-BKT ternary systems with rhombohedral symmetry. BKT ceramics were prepared by the hot-pressing (HP) method, and their ferroelectric and piezoelectric properties were clarified. BKT ceramics doped with a small amount of Bi have a relatively high remanent polarization of Pr = 27.6 microC/cm2 and high piezoelectric properties (k33 = 0.40 and d33 = 101 pC/N). In addition, it was clarified that BKT ceramics have a high Td of approximately 300 degrees C. The solid solution (1-x)BKT-xBaTiO3 (BKT-BT100x) exhibited a high Td of approximately 300 degrees C at x > 0.4.

XAFS Studies of the Behaviour of Bi in Co/Cu Multilayers

The atomic environment of Bi atoms in the Co/Cu multilayered system was studied with X-ray absorption fine structure spectroscopy. Experiments were carried out on a Co(1 nm)/Cu(2 nm) system with 5 and 10 repetitions of Co/Cu evaporated with very low deposition rate in ultrahigh vacuum. A very small amount of Bi (0.06 nm) was deposited on each Cu film in the system. The X-ray absorption fine structure spectra were measured at the BiL3 edge in the X-ray absorption near-edge structure and extended X-ray absorption fine structure ranges at the Beamline X1 of HASYLAB/DESY synchrotron laboratory in Hamburg. The experimental data showed different local neighbourhood of Bi, depending on the number of Co/Cu bilayer repetitions. The results are discussed in terms of the location and segregation of the Bi atoms as well as its possible oxidation ways.

The Behaviour of Surfactants during the Growth of Co/Cu Multilayers

The [Co(1 nm)/Cu(2 nm)]N multilayers with different numbers of bilayer repetitions (N = 3 and 10) were thermally evaporated on Si(100) substrates with a small amount of Bi or Pb deposited only on the first and on the second Cu layer. The chemical composition of the surface after each step of the preparation process was studied by Auger electron spectroscopy. The evolution of the Auger peaks showed the segregation of Bi and Pb surfactants. During the evaporation of the subsequent Co and Cu layers, gradual decrease in the surfactant amount on the surface was observed. No appearance of Co peak on the Cu layer, and Cu peak on the Co layer even for a coverage of a few A indicates the layer continuity. The interface roughness of the surfactant-mediated Co/Cu layers analyzed by X-ray reflectometry (when surfactant was deposited twice) was similar to the pure Co/Cu samples. However, more repetitions of surfactant, by reduction of interface roughness, improve the layer quality.

The effect of surfactants on the growth of Co/Cu multilayers

The effect on the interface structure of multilayers of a pre-deposited ultrathin film of Bi and Pb surfactants introduced into Co/Cu multilayers has been studied. The [Co(1 nm)/Cu(2 nm)] multilayers were thermally evaporated at very low deposition rates with a small amount of Bi and Pb surfactant (about 0.2 ML) introduced at each Cu layer. Auger spectra were taken after subsequent steps of evaporation of Co and Cu, and also after evaporation of surfactants. The evolution of Auger peaks showed that on both Co and Cu surfaces a surfactant peak was always visible. Its intensity continuously increased with the number of Co/Cu repetitions. This shows that the surfactant already segregates to the surface of Co/Cu multilayers during the deposition process. The structure of Co/Cu multilayers with added surfactant has been studied using low-angle X-ray reflectivity. We have found that surfactant addition leads to well-ordered structures with small roughness (a few Å). The results demonstrate that the application of a surfactant during deposition process allows the fabrication of atomically smooth multilayers via a surface segregation mechanism.

Physical properties of Bi-doped CdTe thin films deposited by cosputtering

The structural, morphological, electrical, and optical properties of CdTe–Bi cosputtered thin films related with composition are presented. The films were grown on Corning glass substrates at room temperature from a CdTe–Bi target. The composition measurements show that the Bi content in the films ranges from x = 0.0 to x = 6.37 at%, depending on the area fraction covered by the Bi piece attached to the CdTe target. The structure of the annealed films was determined from X-ray diffraction measurements. Two kinds of structures were observed, depending on the Bi content: (1) CdTe polycrystalline films containing a small amount of Bi that is probably incorporated in the Cd and Te sites of the CdTe lattice. (2) Amorphization of the polycrystalline films, with higher Bi content. From the experimental results, we concluded that using this deposition method n/p-type Bi-doped CdTe polycrystalline films can be produced with electrical resistivity between 102–103 Ω cm and electron mobility between 101 and 102 cm2 V–1 s–1. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Low-temperature (∼250°C) route to lateral growth of ZnO nanowires

Zinc oxide nanowires were obtained through a vapor transport route at temperatures as low as around 250°C. The diameters of the nanowires are ∼40nm and their lengths reach up to a few microns. The high-resolution transmission electron microscopy showed that ZnO nanowires are of hexagonal wurtzite structures with the [112¯0] growth direction. Raman spectrum reveals that the ZnO nanowires are of high-quality crystal and have an oxygen deficiency. The energy dispersive x-ray spectroscopy result verifies that the nanowires contain a small amount of Bi besides Zn and O. The investigation of the growth mechanism suggests that BiI3 plays a key role on the fabrication of ZnO nanowires around 250°C.

Nb/sub 3/Sn wires synthesized by rapid-heating/quenching process of rod-in-tube wire precursors

A rod-in-tube technique (RIT) for the fabrication of Nb/sub 3/Sn precursor wire has been developed. Through this process we expect to increase the volume fraction of A15 phase in the wire, since no bronze remains unlike commercial Nb/sub 3/Sn wires. However, it is very difficult to cold-work a Nb/Sn composite, because pure Sn is too soft compared with Nb, as well known. We found that the hardness of Sn increases with the addition of small amount of Bi, and resulting Nb/Sn-Bi composite wires with 50 m length could be fabricated by the RIT technique. The RHQ (rapid-heating/quenching) process was applied to these strands as the heat treatment technique. The Nb/sub 3/Sn precursor wire has a Ta sheath in order to bear the high temperature RHQ treatment. Although the Nb-Sn supersaturated bcc solid solution was not synthesized, unlike the case of Nb/Al micro composites, the A15 phases formed directly by the RHQ treatment. The maximum T/sub c/ of 18.3 K was obtained, which is slightly higher than that of the bronze-processed Nb/sub 3/Sn. T/sub c/, J/sub c/ (4.2 K) and B/sub c2/ were increased with decreasing peak heating temperature. The addition of Bi seems not to have negative influences on the superconducting properties of Nb/sub 3/Sn.

Interlayer segregation in magnetic multilayers and its influence on exchange coupling

Experimental results show that the exchange coupling field (Hex) of NiFe/FeMn for Ta/NiFe/FeMn/Ta multilayers is higher than that for spin-valve multilayers Ta/NiFe/Cu/NiFe/FeMn/Ta. X-ray photoelectron spectroscopy shows that Cu atoms segregate to the NiFe/FeMn interface for Ta/NiFe/Cu/NiFe/FeMn/Ta multilayers. While studying Ta/X(X=Bi,Pb,Ag,In)/NiFe/FeMn multilayers, we also find that X atoms segregate to the NiFe/FeMn interface, which results in a decrease of the Hex. However, a small amount of Bi, Pb, etc. deposited between Cu and pinned NiFe layer for Ta/NiFe/Cu/NiFe/FeMn/Ta multilayers can increase Hex.

626 オーステナイト系ステンレス鋼溶接部の高温強度データと損傷事例

Many cracks occurred at 308 austenitic stainless welds made by flux cored arc welding(FCAW) process in hot-wall type fluid catalytic cracking(FCC) units operated at a service temperature of more than 640℃ in oil refineries. During investigation the cause of cracking, it was cleared that the high temperature characteristics of these welds such as creep strength at over 640℃ are not fully understood due to little available data. Among many factors that may have caused cracks, a small amount of Bi contained in the weld metals was considered to be the most predominant factor that deteriorated creep ductility and increased reheat cracking susceptibility of the weld metals. This report shows also the results of the effect of welding process and weld metal type on creep rupture properties that contain Bi free and Bi free weld metal.

Bi surfactant effects on ordering in GaInP grown by organometallic vapor-phase epitaxy

The effect of the isoelectronic surfactant Bi on surface structure and ordering has been studied for GaInP semiconductor alloys grown by organometallic vapor-phase epitaxy. A small amount of Bi (trimethylbismuth) added during growth is found to result in disordering for layers grown using conditions that would otherwise produce highly ordered materials. An order of magnitude increase in the step velocity was observed by atomic-force microscopy. Bi completely eliminates three-dimensional islands on the singular (001) surface.

The influence of Bi doping on the in situ growth of TlBa2Ca2Cu3O9 high-Tc films

The in situ process—laser ablation in combination with thermal evaporation of Tl2O—has turned out to be a preparation method for single-phase and epitaxial TlBa2Ca2Cu3O9 (1223) thin films with Tc values up to 109 K. It was found by several groups that a partial substitution of Tl by Bi simplifies the phase development of the 1223 compound in the usual two-step process. We have investigated the influence of the Bi doping on the in situ growth. X-ray measurements show that the films consisted mainly of the 1223 compound. In 300-nm thin films there was no evidence of a Bi amount in the crystal structure, but thinner films (80 nm) show a small amount of Bi. We concluded that Bi doping supports the phase development of the 1223 compound only in an early stage of the film growth. The Bi-doped films have higher Tc values up to 114 K, higher jc values up to 6 × 105 A/cm2 (77 K, 0 T), and lower surface resistances of 56 mΩ (77 K, 87 GHz) than the undoped films.