Bismuth Phase Research Articles

A facile approach to calculating superconducting transition temperatures in the bismuth solid phases

All solid phases of bismuth under pressure, but one, have been experimentally found to superconduct. From Bi-I to Bi-V, avoiding Bi-IV, they become superconductors and perhaps Bi-IV may also become superconductive. To investigate the influence of the electronic properties N(E) and the vibrational properties F(ω) on their superconductivity we have ab initio calculated them for the corresponding experimental crystalline structures, and using a BCS approach have been able to determine their critical temperatures Tc obtaining results close to experiment: For Bi-I (The Wyckoff Phase) we predicted a transition temperature of less than 1.3 mK and a year later a Tc of 0.5 mK was measured; for Bi-II Tc is 3.9 K measured and 3.6 K calculated; Bi-III has a measured Tc of 7 K and 6.5 K calculated for the structure reported by Chen et al., and for Bi-V Tc ~ 8 K measured and 6.8 K calculated. Bi-IV has not been found to be a superconductor, but we have recently predicted a Tc of 4.25 K.

The identification of Вi atoms and clusters in Mg[sbnd]Al silicate glasses

Bi-activated glasses from the MgO-Al2O3-SiO2 system with IR luminescence in the region of 1050–1600 nm have been studied by the high-angle annular dark-field scanning transmission electron microscopy. It was found that individual bismuth ions are present in all samples. Presumably, these ions are Bi3+ with low coordination number in the glass network or the subvalent bismuth cations, namely Bi+ and Bi2+. An increase in the bismuth content, the synthesis temperature together with the change of the synthesis atmosphere from oxidizing (air) to the reducing (nitrogen) leads to the growth of the number of cluster with dimensions in the range of ~3 Å to ~6 Å. The bismuth dimers are very probable in the samples with a bismuth content close to 0.2 at.%. The clusters with bigger size (~12 Å) are most likely to be neutral clusters (Bin)0, which are nuclei for the nano-sized inclusions of the phase of metallic bismuth. In another type of agglomerate with Bi - Bi atoms distances close to 2–4 Å and more correspond the nano-regions enriched in Bi atoms where Bi atoms are embedded in the glass network.

Development of High-Performance Bismuth Sulfide Nanobelts Humidity Sensor and Effect of Humid Environment on its Transport Properties.

Orthorhombic phase bismuth sulfide (Bi2S3) nanobelts were prepared via liquid–solid phase reaction method. Bi2S3 nanobelts were observed to be preferentially oriented along the (101) plane. Direct band gap (2.95 eV) and characteristic wavelength (λmax = 342 nm) were extracted through UV–visible spectroscopy. Specific surface area (9.8 m2/g) and pore size (2.5–120 nm) were evaluated through Brunauer–Emmett–Teller (BET) analysis. Relative humidity (RH) sensing properties were studied in the range of 11–97% RH at ambient conditions. The response of the sensor increases linearly with increase in RH. Fast response time (8–10 s) and recovery time (15 s) were observed. Reproducible and large response was also observed between 11 and 97% RH. Small hysteresis (<5%) and long-term stability during 30 days were confirmed. As a function of frequency, capacitance, alternating current conductivity, and electrical complex modulus in the frequency range of 20–2 MHz were studied at 11–97% RH. The sensing mechanism was also studied.

Dye Mixtures Degradation by Multi-Phase BiVO&lt;sub&gt;4&lt;/sub&gt; Photocatalyst

The objective of this research was to prepare multi–phase bismuth vanadate (BiVO4) powder using the solvothermal method to be used as a photocatalyst. In the preparation step, bismuth nitrate and ammonium vanadate were used as the precursors with a mole ratio of 1:1. The mixed solution was diluted to 0.025 M with acetic acid and heated at 200 °C for 2 h in a Teflon–lined stainless steel autoclave vessel. Multi–phase BiVO4was obtained without calcination step. Multi–phase BiVO4was characterized by X–ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT–IR), and energy dispersive spectroscopy (EDS). The efficiency of multi–phase BiVO4for photocatalytic degradation of the mixed dye of methylene blue (MB) and rhodamine B (RhB) solution under UV light irradiation was studied. The concentration of the mixed dye solution was measured by UV–Vis spectrophotometry (UV–Vis). The effect of concentration of catalyst and pH of solution was studied. The optimum conditions for photocatalytic degradation of mixed dye solution were obtained at 0.8 g/L for concentration of multi–phase BiVO4and 7.78 for initial pH of the mixed dye solution.

Superconductivity of Bi-III phase of elemental bismuth: Insights from muon-spin rotation and density functional theory

Using muon-spin rotation the pressure-induced superconductivity in the Bi-III phase of elemental Bismuth (transition temperature $T_{\rm c}\simeq7.05$ K) was investigated. The Ginzburg-Landau parameter $\kappa=\lambda/\xi=30(6)$ ($\lambda$ is the magnetic penetration depth, $\xi$ is the coherence length) was estimated which is the highest among single element superconductors. The temperature dependence of the superconducting energy gap [$\Delta(T)$] reconstructed from $\lambda^{-2}(T)$ deviates from the weak-coupled BCS prediction. The coupling strength $2\Delta/k_{\rm B}T_{\rm c}\simeq 4.34$ was estimated thus implying that Bi-III stays within the strong coupling regime. The Density Functional Theory calculations suggest that superconductivity in Bi-III could be described within the Eliashberg approach with the characteristic phonon frequency $\omega_{\rm ln}\simeq 5.5$ meV. An alternative pairing mechanism to the electron-phonon coupling involves the possibility of Cooper pairing induced by the Fermi surface nesting.

Real-Time Observation of a Coherent Lattice Transformation into a High-Symmetry Phase

Excursions far from their equilibrium structures can bring crystalline solids through collective transformations including transitions into new phases that may be transient or long-lived. The direct spectroscopic observation of far-from-equilibrium rearrangements provides fundamental mechanistic insight into chemical and structural transformations and a potential route to practical applications, including ultrafast optical control over material structure and properties. However, in many cases, photoinduced transitions are irreversible or only slowly reversible, or the light fluence required exceeds material damage thresholds. This requirement precludes conventional ultrafast spectroscopy, in which optical excitation and probe pulses irradiate the sample many times, each measurement providing information about the sample response at just one probe delay time following excitation, with each measurement at a high repetition rate and with the sample fully recovering its initial state in between measurements. Using a single-shot, real-time measurement method, we are able to observe the photoinduced phase transition from the semimetallic, low-symmetry phase of crystalline bismuth into a high-symmetry phase whose existence at high electronic excitation densities is predicted based on earlier measurements at moderate excitation densities below the damage threshold. Our observations indicate that coherent lattice vibrational motion launched upon photoexcitation with an incident fluence above 10 mJ/cm2 in bulk bismuth brings the lattice structure directly into the high-symmetry configuration for several picoseconds, after which carrier relaxation and diffusion restore the equilibrium lattice configuration. Published by the American Physical Society 2018

Electrochemical hydrogen evolution and storage studies on bismuth nano hexagons

Bismuth nano hexagons were synthesized using potentiostatic electrodeposition and studied for their performance towards electrochemical hydrogen storage and evolution. Regular hexagons with edge length ≈ 500 nm and thickness ≈ 80 nm were observed in scanning electron microscopy (SEM). X-ray diffraction (XRD) pattern indicates the presence of poly-crystalline bismuth and bismuth oxide in rhombohedral and cubic phases respectively. X-ray photoelectron spectroscopy (XPS) studies further confirm the presence of two phases of bismuth i.e. elemental bismuth and bismuth (III) oxide. Results indicate that these nano hexagons show good hydrogen ion (H+) storage and successive hydrogen gas (H2) evolution characteristics.

Molten core fabrication of bismuth germanium oxide Bi4Ge3O12 crystalline core fibers

AbstractOptical fibers possessing a crystalline oxide core have significant potential for novel and useful electro‐ or nonlinear‐optic waveguides. Presently, however, their utility suffers from the slow speed and limited cladding materials afforded by conventional crystal‐fiber‐growth techniques. Described herein is the development of single phase bismuth germanium oxide crystalline core fibers using conventional glass fiber drawing. More specifically, fibers were fabricated and evaluated based on 2 embodiments of the molten core method. In a first approach, a Bi4Ge3O12 single crystal was employed as the precursor and sleeved inside a borosilicate glass cladding. In the second approach, additional Bi2O3 was included along with the Bi4Ge3O12 precursor single crystal. Glass clad fibers drawn from the precursor Bi4Ge3O12 single crystal resulted in a polycrystalline core with various crystal morphologies (line‐like, dendrite‐like, and uniform grains) as will be discussed, while fibers drawn from the Bi4Ge3O12 single crystal surrounded by Bi2O3 resulted in a more homogeneous microstructure. The eulytine crystal structure was crystallized using both approaches, with the formation of a secondary crystal phase using the second approach. More particularly, this work aims at showing that single phase and phase pure crystalline oxide core optical fibers can be achieved using conventional glass fiber draw processes, although further optimization is necessary for obtaining single crystalline core fibers.

Synthesis, characterization and luminescent properties of mixed phase bismuth molybdate-doped with Eu3+ ions

Red phosphors of Eu[Formula: see text]-doped bismuth molybdate (BMO) are prepared by a low temperature hydrothermal method assisting with Phenol Formaldehyde resin (PFr), and characterized by X-ray diffraction (XRD) patterns, Fourier transform infrared-spectroscopy (FT-IR), thermogravimetric analyzer (TGA), differential thermal analyzer (DTA), and photoluminescence (PL) spectroscopy. PL properties influence factors including molar ratio of Bi[Formula: see text] and Mo[Formula: see text] ions, PFr dosage and dopants concentration are discussed in detail. The results show that BMO can act as a useful host for Eu[Formula: see text] ions doping, and energy transferring from Bi[Formula: see text] to Eu[Formula: see text] achieved efficiently, the BMO phosphors displayed intense red color emission under ultraviolet light excitation.

Mechanical Coating of Zinc Particles with Bi2O3-Li2O-ZnO Glasses as Anode Material for Rechargeable Zinc-Based Batteries

The electrochemical performance of zinc particles with 250 μm and 30 μm diameters, coated with Bi2O3-Li2O-ZnO glass is investigated and compared with noncoated zinc particles. Galvanostatic investigations were conducted in the form of complete discharge and charging cycles in electrolyte excess. Coated 30 μm zinc particles provide the best rechargeability after complete discharge. The coatings reached an average charge capacity over 20 cycles of 113 mAh/g compared to the known zero rechargeability of uncoated zinc particles. Proposed reasons for the prolonged cycle life are effective immobilization of discharge products in the glass layer and the formation of percolating metallic bismuth and zinc phases, forming a conductive network through the glass matrix. The coating itself is carried out by mechanical ball milling. Different coating parameters and the resulting coating quality as well as their influence on the passivation and on the rechargeability of zinc–glass composites is investigated. Optimized coating qualities with respect to adhesion, homogeneity and compactness of the glass layer are achieved at defined preparation conditions, providing a glass coating content of almost 5 wt % for 250 μm zinc particles and almost 11 wt % for 30 μm zinc particles.

In Situ Synthesis of Bi2O3 Nanoparticles on ZincMe (Me=Al or Cr) Layered Double Hydroxide Frameworks for Photocatalytic Oxygen Evolution from Water under Solar‐Light Activation

AbstractA key target to boost solar‐to‐chemical conversion processes is to fabricate an efficient solar‐light‐responsive photocatalyst. Herein, we report the in situ synthesis of nanoparticles (NPs) of Bi2O3 directly on Zn‐based layered double hydroxide (LDHs) frameworks. The in situ synthesis of Bi2O3NPs is done at room temperature, is ligand free and explores the ability of calcined ZnMeLDHs to reconstruct their layered structures in Bi(NO3)3 aqueous solution. The in situ formation of Bi2O3NPs on ZnMeLDHs is assessed by transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), powder X‐ray diffraction (XRD), and UV/Vis spectroscopy and compared with the features of a corresponding Bi2O3NPs/LDH prepared by the conventional impregnation route. The rapid photocatalytic response of the Bi2O3NPs/ZnMeLDH (Me=Al, Cr) heterostructures is confirmed by O2 generation from water under solar‐light irradiation. The rate of O2 generation increases by a factor of approximately 2 for the ZnCrLDH based catalysts as compared to that of the family of ZnAlLDH catalysts. Further, the presence of the bismuth phase and its nano‐dimension leads to increased efficiency for the in situ prepared Bi2O3NPs/LDHs as compared to that of impregnated Bi2O3/LDH and the pristine LDHs.

P.7.b.017 - Genes involved in the genetics of ADHD are enriched in mutations associated with verbal memory in schizophrenia

To obtain the equation of state of liquid bismuth and its melting curve, ultrasonic velocity measurements were performed in a multi-anvil apparatus. Using a series of thermodynamic relationships, we extract the volume of liquid bismuth as functions of pressure and temperature up to 973 K and 4.3 GPa. We also introduce a calculation process to build the thermal equations of state of each phase of solid bismuth based on their phase transition boundaries. Combining the thermodynamic parameters of liquid and solid bismuth, we employ the Gibbs equation and the Clausius-Clapeyron equation and finally derive the melting curve up to 8 GPa, which shows excellent consistency with most previous theoretical and experimental results. These results not only demonstrate the accuracy of our experimental and theoretical methods, but also demonstrate the feasibility of the thermodynamic method for obtaining unknown melting curves.

Equation of state of liquid bismuth and its melting curve from ultrasonic investigation at high pressure

To obtain the equation of state of liquid bismuth and its melting curve, ultrasonic velocity measurements were performed in a multi-anvil apparatus. Using a series of thermodynamic relationships, we extract the volume of liquid bismuth as functions of pressure and temperature up to 973K and 4.3GPa. We also introduce a calculation process to build the thermal equations of state of each phase of solid bismuth based on their phase transition boundaries. Combining the thermodynamic parameters of liquid and solid bismuth, we employ the Gibbs equation and the Clausius-Clapeyron equation and finally derive the melting curve up to 8GPa, which shows excellent consistency with most previous theoretical and experimental results. These results not only demonstrate the accuracy of our experimental and theoretical methods, but also demonstrate the feasibility of the thermodynamic method for obtaining unknown melting curves.

Multiferroicity in sol–gel synthesized Sr/Mn co-doped BiFeO3 nanoparticles

A simple and cost effective sol–gel auto-combustion technique was used to synthesize Bi0.9Sr0.1Fe1−xMnxO3 (x = 0, 0.05, 0.10, 0.15 and 0.20) multiferroics. Rietveld’s refined X-ray diffraction patterns validated the synthesis of pure phase bismuth ferrite nanoparticles adopting a rhombohedrally distorted ABO3 type perovskite structure with space group R3c. Morphology of the prepared samples manifested the improved crystallinity with increasing Mn contents in BiFeO3. Uniformly distributed multi-shaped grains having varying sizes were formed after combustion which would affect the microstructural related properties of the parent compound. Energy dispersive X-ray spectroscopy confirmed the presence of the relevant elements in the prepared compositions according to their stoichiometric ratio. Enhanced saturation magnetization was observed with increasing doping concentration in the parent compound. Improved polarization versus electric field loops were observed in Mn and Sr co-doped BiFeO3 nanoparticles. All the properties in the present research work have been explained on the basis of dopants and their concentrations, phase purity, microstructure and grain sizes.

Direct Liquid Injection Chemical Vapor Deposition of Molybdenum-Doped Bismuth Vanadate Photoelectrodes for Efficient Solar Water Splitting

The direct liquid injection chemical vapor deposition (DLI-CVD) method is used to grow pristine and molybdenum (Mo)-doped monoclinic scheelite phase bismuth vanadate (BVO) photoelectrodes. Superior photoelectrochemical (PEC) performance is achieved with ∼200 ± 50 nm thick pristine and 8 at. % Mo-doped BVO films grown at 550 °C. Photocurrent densities as high as ∼1.65 and 3.25 mA/cm2 are obtained for pristine and optimum 8% Mo-doped BVO electrodes, respectively, at 1.23 V vs reversible hydrogen electrode (RHE) under visible light AM 1.5G (100 mW/cm2) in 0.5 M phosphate buffer electrolyte in the presence of 0.1 M Na2SO3 hole scavenger. Somewhat lower photocurrent densities of ∼1.5 and 2.4 mA/cm2 are obtained for pristine and optimum 8% Mo-doped BVO electrodes, respectively, in the absence of Na2SO3. Onset potential values as low as ∼0.1 and 0.3 V vs RHE are achieved with pristine and Mo-doped BVO films for sulfite and water oxidation, respectively. The increased photocurrent density with Mo doping is attrib...

A metastable liquid melted from a crystalline solid under decompression

A metastable liquid may exist under supercooling, sustaining the liquid below the melting point such as supercooled water and silicon. It may also exist as a transient state in solid–solid transitions, as demonstrated in recent studies of colloidal particles and glass-forming metallic systems. One important question is whether a crystalline solid may directly melt into a sustainable metastable liquid. By thermal heating, a crystalline solid will always melt into a liquid above the melting point. Here we report that a high-pressure crystalline phase of bismuth can melt into a metastable liquid below the melting line through a decompression process. The decompression-induced metastable liquid can be maintained for hours in static conditions, and transform to crystalline phases when external perturbations, such as heating and cooling, are applied. It occurs in the pressure–temperature region similar to where the supercooled liquid Bi is observed. Akin to supercooled liquid, the pressure-induced metastable liquid may be more ubiquitous than we thought.

Photocatalytic water oxidation at bismuth vanadate thin film electrodes grown by direct liquid injection chemical vapor deposition method

Photoelectrochemical cells (PECs) are devices that can harvest and convert solar energy to produce consumable fuel, e.g. by splitting water into oxygen and hydrogen. Photocatalytic semiconductor materials play a major role in PECs, and their overall efficiency is usually limited by short carrier diffusion length because of structural defects, poor light absorptivity, and sluggish kinetics of photoelectrochemical reactions at the semiconductor electrode. Synthesis of high quality defect-free semiconductor materials using high temperature deposition techniques generally yield films with good adhesion to substrates while improving charge carrier transport and hence the overall efficiency of a PEC. A direct liquid injection chemical vapor deposition (DLI-CVD) technique has been utilized to synthesize monoclinic clinobisvanite phase bismuth vanadate (BiVO4) films for photocatalytic water oxidation. The technique yields dense high quality epitaxial and polycrystalline BiVO4 films on Yttria stabilized zirconia (YSZ) and Fluorine doped tin oxide (FTO) substrates, respectively, at growth temperature in the range of 500–550 °C. The photoelectrochemical characteristics of the films grown on FTO have been studied and a photocurrent value of 2.1 mA/cm2 at 1.23 V vs Normal hydrogen electrode (NHE) (0.5 V vs. Ag/AgCl), with onset potential values as low as 0.23 V vs. NHE (−0.5 V vs. Ag/AgCl), are obtained despite the low porosity of the films. The PEC performance is further improved by synthesizing BiVO4 directly on top of a tungsten oxide interlayer and modifying its surface with FeOOH co-catalyst.

Multiferroic Based Microwave Devices

Recently, there has been significant interest on the fundamental science and technological applications of complex oxides and multiferroics. Low-power multiferroic have potential to fabricate and characterize frequency tunable, compatible with MMIC Technology, small light-weight for hand-held operation, cost-effective, high-frequency (>10GHz), devices for next generation communication devices and military applications. Multiferroic materials consists of both magnetic and ferroelectric phase and they offer the possibility of magneto-electric (ME) coupling. The purpose of this research is to show strong magnetic field dependent frequency tuning of multiferroics (Nickel doped BFO – BiFe1-xNixO3) based devices over a broad frequency band. We have shown here the magnetic field control of ferromagnetic resonance (FMR) field/frequency from C to Ku band frequencies. Nanoparticles of BiFe1xNixO3 (x=0.025 & 0.05) were prepared by auto combustion method. The XRD study confirms the formation of pure phase Bismuth Ferrite Nanoparticles. Ferromagnetism of un-doped BFO was enhanced by Ni substitution. Microwave characterization was done in co-planar waveguide (CPW) geometry both in field sweep and frequency sweep mode. BiFe1-xNixO3 nanoparticles were deposited using electrophoretic deposition method (EPD) on top of CPW to do the FMR experiments. The operating frequency of the device was tuned by application of magnetic field (H) over a wide range (5 to 20 GHz) with a field up to 8 kOe. Copyright © 2016 VBRI Press

Single and bilayer bismuthene: Stability at high temperature and mechanical and electronic properties

Based on first-principles phonon and finite temperature molecular dynamics calculations including spin-orbit coupling, we showed that free-standing single-layer phases of bismuth, namely buckled honeycomb and asymmetric washboard structures named as bismuthene, are stable at high temperature. We studied the atomic structure, mechanical, and electronic properties of these single-layer bismuthene phases and their bilayers. The spin-orbit coupling is found to be crucial in determining lattice constants, phonon frequencies, band gaps, and cohesion. In particular, phonons of 3D hexagonal crystal, as well as those of single-layer bismuthene phases, are softened with spin orbit coupling. By going from 3D hexagonal crystal to free-standing single-layer structures, 2D hexagonal lattice is compressed and semimetal is transformed to semiconductor as a result of confinement effect. On the contrary, by going from single-layer to bilayer bismuthenes, the lattice is slightly expanded and fundamental band gaps are narrowed. Our results reveals that interlayer coupling in multilayer and 3D Bi crystal is crucial for topologically trivial to nontrivial and semimetal to semiconductor transitions.

Conversion reaction mechanisms of cubic bismuth phosphate Bi13.1POδ as cathode in lithium-ion batteries

Compounds containing bismuth ions (Bi3+) as cathodes used in lithium-ion batteries based on chemical conversion reaction were supposed to be the most promising cathodes. They were considered to break through the storage capacity because a Bi atom could react with three Li+ ions and simultaneously transfer three electrons at a time during conversion reaction. In the paper, the cubic phase bismuth phosphate Bi13.1POδ as cathode used in lithium-ion batteries was proposed. The results showed that the crystalline Bi13.1POδ with sizes of 2–5 μm synthesized via hydrothermal method possessed excellent capacities and poor cycling stability. The initial discharge and charge capacities reached to 706 and 419 mAh g−1 at current density of 39.06 mA g−1. To improve the cycling stability of the cathode material, the chemical conversion process was focused on investigation. The elemental analyses indicated that the ratio of Bi:P ratio was decreased from 12.98 to 4.00, which suggests that about 8 Bi atoms participated in the reaction. Therefore, the capacities of the material were very high. The reduced Bi transformed from the beginning isolated state to ribbon or plate one, and coated on the surface of the active materials, inhibiting further conversion reaction. Consequently, the cycling stability of the cathode material was less than the capacity performance.