Bismuth Single Crystals Research Articles

Single-crystal oxygen-rich bismuth oxybromide nanosheets with highly exposed defective {10–1} facets for the selective oxidation of toluene under blue LED irradiation

Reactive radicals are crucial for activating inert and low-polarity C(sp3)-H bonds for the fabrication of high value-added products. Herein, novel single-crystal oxygen-rich bismuth oxybromide nanosheets (Bi4O5Br2 SCNs) with more than 85 % {10–1} facets exposure and oxygen defects were synthesized via a facile solvothermal route. The Bi4O5Br2 SCNs demonstrated excellent photocatalytic performance in the selective oxidation of toluene under blue light. The yield of benzaldehyde was 1876.66 μmol g−1 h−1, with a selectivity of approximately 90 %. Compared to that of polycrystalline Bi4O5Br2 nanosheets (Bi4O5Br2 PCNs), the activity of Bi4O5Br2 SCNs exhibit a 21-fold increase. Experimental studies and density functional theory (DFT) calculations have demonstrated that the defect Bi4O5Br2 (10–1) facets exhibits exceptional adsorption properties for O2 molecules. In addition, the single-crystal structure in the presence of surface defects significantly increases the separation and transport of photogenerated carriers, resulting in the effective activation of adsorbed O2 into superoxide radicals (•O2–). Subsequently, the positively charged phenylmethyl H is readily linked to the negatively charged superoxide radical anion, thereby activating the CH bond. This study offers a fresh perspective and valuable insights into the development of efficient molecular oxygen-activated photocatalysts and their application in the selective catalytic conversion of aromatic C(sp3)-H bonds.

Porous bismuth nanocrystals with advanced sodium ion storage property

Bismuth-based materials are ideal electrodes for sodium-ion batteries (SIBs) due to their high capacity and low cost. However, conventional solid bismuth materials still suffer from severe volume expansion during the reaction process, which hinders its application. Herein, single-crystal bismuth nanospheres with diameters in the range of 200–400 ​nm were successfully prepared with the Na–Bi alloying mechanism studied using in-situ XRD, which confirms a stepwise process of Bi→NaBi→Na3Bi with large volume variation. To address the volume change issue, we introduce a porous structure into the bulk of Bi crystals, which alleviated its volume expansion and suppressed its cyclic failure. An in-situ TEM experiment is further carried out to verify this effective structure-modification strategy, demonstrating its applicable feature for electrode design and performance enhancement.

Shubnikov-de Haas (SdH) Oscillation in Self-Flux Grown Rhombohedral Single-Crystalline Bismuth

The historic de Haas-van Alphen effect observed in the late 1950s in CSIR-NPL by J.S. Dhillon and D. Shoenberg in pure bismuth and zinc metal is revisited in this article through a single-crystalline phase of bismuth crystal, which is observed in terms of resistivity as predicted by Shubnikov-de Haas (SdH) oscillations. The single crystal of bismuth is grown through solid-state reaction under an optimized heat treatment whose purity and structural phase are confirmed through XRD, SEM, and EDAX. The transport properties of single crystal show the presence of SdH oscillations from a temperature range of 2 to 10 K. The occurrence of oscillations in the transverse magnetic field confirms the presence of the Fermi surface. Landau level (LL) fan diagram reveals the presence of topological surface states and the Berry’s phase confirmation from temperature-dependent SdH oscillations, concluding the presence of a noble topological phase of bismuth exhibiting SdH oscillations.

Facile synthesis of bismuth nanoparticles for efficient self-powered broadband photodetector application

Bismuth, an emerging topological insulator, has attracted great interest due to its fascinating properties. Herein, a facile, environmentally friendly, and low-cost solvothermal route was proposed to synthesize high-quality single-crystal bismuth nanoparticles. The performance of bismuth nanoparticles photoelectrochemical-type photodetector has been systematically evaluated. The responsivity spectrum shows that the bismuth nanoparticles photodetector has a broad response range from ultraviolet (UV) to near-infrared (NIR), with the highest responsivity of 4.979 mA/W at a wavelength of 405 nm without bias. Additionally, the device exhibits a fast response speed (tr < 12 ms, td < 46 ms) and a high specific detectivity (3.71 × 1010 Jones). These results indicate that bismuth nanoparticles have great potential in the application of self-powered broadband photodetectors with high responsivity. Moreover, the working mechanism of bismuth nanoparticles photodetector was proposed.

Bismuth nanowires with in situ shadow deposited Josephson junctions

Single crystal bismuth nanowires have been recently identified as a high-order topological system, in which the crystal “hinges” host a one dimensional helical transport channel. To date, studies on the superconducting transport in these channels have relied on an aggressive surface treatment required to strip the oxidized nanowire surface prior to deposition of a superconductor in a process that will inevitably cause some damage to the surface. In this report, we describe the growth and characterization of bismuth nanowires with in situ deposited superconducting contacts, which avoid the requirement to treat the nanowire surface for oxide removal. The described shadow deposition method may avoid damage to the bismuth nanowire surface, supplying a higher-quality platform for exploring the topological quantum transport in bismuth nanowire based Josephson junctions.

Analysis of temperature dependencies of transport coefficients for a single-crystal bismuth wire with a 1.90-μm diameter

We measured the temperature dependencies of resistivity, Seebeck coefficient, magnetoresistivity, and Hall coefficient from 20 to 300 K for an individual single-crystal bismuth wire with a diameter of 1.90 μm and a length of 1554 μm. The wire was embedded in a quartz glass after making local electrodes on the wire through a nanofabrication process. The temperature dependencies were investigated using a model that considered not only the wire diameter, crystal orientation, band structure, and Fermi surface of the bismuth, but also the scattering process and mean free path of the carrier. We were able to explain the dependencies of resistivity and Seebeck coefficient on the contribution of each carrier pocket for the bismuth wire. The results showed that the specific conductivity of the carrier pocket of bismuth was dominant in the lower temperature region due to the wire geometry. As a result, the characteristic temperature dependence of resistivity was observed. Furthermore, the temperature dependence of the Hall coefficient was estimated using conductivity, and the data indicated that the experimental and calculation results were in good agreement.

Resonant torque differential magnetometry with high frequency quartz oscillators.

Sensitive magnetometry has been a powerful probe for investigating quantum materials. Extreme conditions, such as sub-kelvin cryogenic temperatures and ultrahigh magnetic fields, demand further durability for sensitive magnetometry. However, significant mechanical vibrations and rapid magnetic field changes give enormous challenges to conventional magnetometry. This article presents a possible solution to this problem by developing a new magnetometry technique using high-frequency quartz oscillators. The technique takes advantage of the symmetry and geometry of mechanical vibration configurations of standard commercially available MHz quartz oscillators, and the setup keeps the high quality factor resonance with the sample mounted on the oscillator. We further demonstrate the sensitivity of the technique using bismuth single crystals and a Fe0.25TaS2 ferromagnetic material. Quantum oscillations are observed in the magnetometry response below 1T, and the detected oscillation frequency is shown to come from the electron pockets of the bismuth.

Temperature dependence of resistivity and temperature coefficient of a single-crystal bismuth nanowire based on the varying scattering mechanism

Temperature dependence of resistivity and temperature coefficient of a single-crystal bismuth nanowire was investigated considering the scattering mechanism for each Fermi pocket of the carrier using relaxation time approximation based on the Boltzmann equation. The scattering mechanism of each bismuth carrier was determined according to the relationship between the mean free path of bulk bismuth and nanowire (diameter: 595 and 345 nm). The calculation and experimental results revealed the dominant contribution of the bulk segment in the room-temperature region, influencing the scattering mechanism, whereas the dominant contribution of the wire segment was observed in the lower-temperature region owing to the substantially larger mean free path of the carrier than the wire diameter. Moreover, the temperature coefficient in the lower-temperature region was determined by the effective masses parallel and perpendicular to the wire length, verifying the unique behavior of the temperature dependence of bismuth nanowires with three-dimensional density of state.

Heat fluxes measurement on the shocktube wall

In this paper we carried out experimental study of a heat flux on the shocktube surface during passage of shock wave using a gradient sensor based on bismuth single crystal. The obtained experimental data were compared with numerical simulation results. It is shown that after passing through contact surface that separating the hot &amp;quot;plug&amp;quot; and pushing gas, the colder gas flow is mixed with the hot one. The heat transfer on the contact surface was evaluated. Keywords: shock tube, heat flux, non-stationary heat measurements.

Измерение тепловых потоков на стенке ударной трубы

In this paper we carried out experimental study of a heat flux on the shocktube surface during passage of shock wave using a gradient sensor based on bismuth single crystal. The obtained experimental data were compared with numerical simulation results. It is shown that after passing through contact surface that separating the hot "plug" and pushing gas, the colder gas flow is mixed with the hot one. The heat transfer on the contact surface was evaluated.

A comparative study of promising filter materials for neutron imaging facilities

The effect of sapphire and bismuth single-crystal filters and their combinations on the quality of neutron radiographic images and neutron tomography data has been studied. The parameters of the contrast of the neutron image were analyzed depending on the monocrystalline filters. Neutron transmission spectra were obtained for sapphire and bismuth single crystals. Additionally, the effect of filters on the overall intensity of the thermal neutron beam and the background of gamma-rays was investigated. Based on the obtained data, we assume that a single-crystal sapphire filter can be most effectively used for radiographic and tomographic installations using thermal neutrons.

Single-Crystal Bismuth Thiophosphate, BiPS4, as a Nontoxic and Mechanically Robust X-ray Detector.

Bismuth thiophosphate, BiPS4, is a promising nontoxic, high-density ternary chalcogenide semiconductor. Polycrystalline BiPS4 was synthesized from the stoichiometric melt of Bi, P, and S. Phosphorus was purified via an in-situ sublimation method. Single crystals of BiPS4 were grown using a modified vertical Bridgman method with a thermal gradient of 18 °C/cm. The material exhibits an electrical resistivity of 2 × 109 Ω·cm. The Knoop hardness of the single crystals is 128 ± 0.8 kg mm-2. A blocking contact behavior was observed with asymmetric contacts of Ga/BiPS4/Ag. A clear photocurrent response was observed from a BiPS4 crystal under an electric field as low as 1.14 V mm-1. Using a tungsten X-ray source, an X-ray sensitivity of 52 μ Gy-1 cm-2 was measured under an electric field of 80 V mm-1. When a single-crystal BiPS4 radiation detector device was used in a pulse-height radiation detection system, a clear charge collection response was observed under a 241Am α-particle radiation source.

Heat transfer enhancement during condensation of water steam on inclined pipe

This paper presents experimental study of heat transfer during film condensation of saturated water steam on the outer surface of the inclined pipe by gradient heatmetry. Heat flux per unit area was measured by gradient heat flux sensors made of a single-crystal bismuth. The experimental results are presented in the graphs of heat flux per unit area dependence on time and azimuthal angle. The highest average heat transfer coefficient during condensation of α = 6.94 kW/(m2 • K) was observed when the pipe was inclined at the angle of ψ = 20 °. This value exceeds one obtained on a vertical pipe by 14.9 %. Heat transfer enhancement during condensation of saturated water steam on inclined pipe is associated with changes in condensate film flow. Another part of experiments was made by simultaneously using of gradient heatmetry and condensate flow visualization. Experimental results confirmed the applicability and high informative content of proposed comprehensive method. Comprehensive study of heat transfer during condensation confirmed that heat flux per unit area pulsations may be explained by the formation of individual drops, their coalescence, and drainage from the sensor surface.

Improved electrical conductivity and power factor in Sn and Se co-doped melt-grown Bi2Te3 single crystal

In the current work, growth and thermoelectric characterization of tin and selenium co-doped single crystal bismuth telluride have been carried out in the range of temperature 10–400 K. The crystals show hexagonal crystal structure with Roverline{3 }m space group. The direction of growth, quality of the single crystals, the density of dislocation, and dopants effect on the inner plane structure of the crystals have been analyzed through high-resolution X-ray diffraction study. Energy dispersive analysis of X-rays approves the elemental composition, and field emission scanning electron microscopy shows uniform growth with micro precipitates on the surface of the crystals. Quasi degenerate and non-degenerate electrical resistivity is observed in the pristine and doped samples, respectively. Temperature-dependent Seebeck coefficient measurements confirm the n-type semiconducting nature of the pristine as well as doped samples. Temperature-dependent power factor of (Bi0.96Sn0.04)2Te2.7Se0.3 is found to increase by 1.1 times, and electrical resistivity reduced by 3.3 times as compared to pristine Bi2Te3.

Abnormal transport properties of Bi-III superconducting phase in pressurized bismuth single crystal

Resistivity, magnetoresistance, and upper critical field, have been comprehensively studied for the bismuth (Bi)-III superconducting phase in the pressure range of 2.9 GPa ⩽ P⩽ 6.2 GPa. It is discovered that the transition temperature T c of the Bi-III phase is gradually suppressed with increasing pressure. Strikingly, the temperature-dependent resistivity above T c in the Bi-III region reveals notable non-Fermi-liquid behaviors, resembling many unconventional superconducting systems. As the pressure increases, the magnetoresistance effect progressively grows and reaches a maximum value of 212% at pressure ∼6.2 GPa and field of 5 T, indicating a possible contribution to the charge conduction by Dirac electrons. Moreover, the zero-temperature upper critical field for the Bi-III phase displays relatively low values concerning the moderate T c values, and the reduced upper critical field for different pressures deviates from the single-band Werthamer–Helfand–Hohenberg model. These unusual normal state transport properties and unique behavior of the upper critical field point to possible unconventional superconductivity for the Bi-III superconducting phase.

Measurement of Essentially Nonstationary Heat Fluxes by a Bismuth-Based Gradient Sensor

The gradient heat flux sensor made of a bismuth single crystal is calibrated. The volt–watt sensitivity of the sensor is determined and the method of data processing based on the 1D heat conduction equation for a thin plate is proposed. This method is tested on experimental data obtained for the initiation of a laser discharge in a calm atmosphere and in a supersonic gas flow.

Измерение существенно нестационарных тепловых потоков градиентным датчиком на основе висмута

In this work we performed calibration of the gradient heat flux sensor made of bismuth single crystal. The value of the volt-watt sensitivity of the sensor is found and a data processing method based on the one-dimensional heat equation for a thin plate is presented. An experimental study of the heat flux on the frontal surface of the cylinder after a laser discharge was carried out. The data obtained as a result of the experiment were processed by the proposed method.

Electron-Transparent Thermoelectric Coolers Demonstrated with Nanoparticle and Condensation Thermometry

More efficient thermoelectric devices would revolutionize refrigeration and energy production, and low-dimensional thermoelectric materials are predicted to be more efficient than their bulk counterparts. But nanoscale thermoelectric devices generate thermal gradients on length scales that are too small to resolve with traditional thermometry methods. Here we fabricate, using single-crystal bismuth telluride (Bi2Te3) and antimony/bismuth telluride (Sb2-xBixTe3) flakes exfoliated from commercially available bulk materials, functional thermoelectric coolers (TECs) that are only 100 nm thick. These devices are the smallest TECs ever demonstrated by a factor of 104. After depositing indium nanoparticles to serve as nanothermometers, we measure the heating and cooling produced by the devices with plasmon energy expansion thermometry (PEET), a high-spatial-resolution, transmission electron microscopy (TEM)-based thermometry technique, demonstrating a ΔT = -21 ± 4 K from room temperature. We also establish proof-of-concept for condensation thermometry, a quantitative temperature-change mapping technique with a spatial precision of ≲300 nm.

Temperature dependent terahertz giant anisotropy and cycloidal spin wave modes in BiFeO3 single crystal**Project supported by the National Natural Science Foundation of China (Grant Nos. 61975110, 11674213, 61735010, and 11604202), the 111 Project, China (Grant No. D18014), the International Joint Lab Program supported by Science and Technology Commission Shanghai Municipality, China (Grant No. 17590750300), the Key Project supported by Science

THz time-domain spectroscopy (THz-TDS) is used to study the THz-optical properties of a single crystal bismuth ferrite BiFeO3 (BFO). It can be found that the anisotropy of BiFeO3 is strongly dependent on the temperature. A giant birefringence up to around 3.6 is observed at 1 THz. The presence of a spatially modulated cycloidal antiferromagnetic structure leads to spin cycloid resonances (SCR) ψ and Φ, corresponding to the out-of-plane and in-plane modes of the spin cycloid, respectively. We distinguish the SCR with respect to their response to orthogonal polarizations of the electric fields of the incident THz beam. In addition, we observe a resonance appearing below 140 K, which might be interpreted as an electromagnon mode and related to a spin reorientation transition. Our present observations present that the temperature and polarization, as the external control parameters, can be used to modulate the THz optical properties of BFO single crystal.

Atomic Force Microscopy Determination of the Direction of Dislocation Lines in Single Crystals of Bismuth and Its Alloys

A technique for determining the directions of dislocation lines using an atomic force microscope after selective etching of a single crystal is discussed. The technique has been tested on bismuth-type single crystals.