Bismuth Oxide Layer Research Articles

Converting an O-vacancy-rich oxide into a multifunctional separator modifier for long-lifespan lithium metal batteries

The lithium metal anode is hailed as the desired “holy grail” for the forthcoming generation of high-energy-density batteries, given its astounding theoretical capacity and low potential. Nonetheless, the formation and growth of dendrites seriously compromise battery life and safety. Herein, an yttria-stabilized bismuth oxide (YSB) layer is fabricated on the polypropylene (PP) separator, where YSB reacts with Li anode in-situ in the cell to form a multi-component composite interlayer consisting of Li3Bi, Li2O, and Y2O3. The interlayer can function not only as a redistributor to regulate Li+ distribution but also as an anion adsorber to increase the Li+ transference number from 0.37 to 0.79 for suppressing dendrite nucleation and growth. Consequently, compared with the cell with a baseline separator, those with modified separators exhibit prolonged lifespan in both Li/Li symmetrical cells and Li/Cu half-cells. Notably, the full cells coupled with ultrahigh-loading LiFePO4 display an excellent cycling performance of 1700 cycles with a high capacity retention of ∼80% at 1 C, exhibiting great potential for practical applications. This work provides a feasible and effective new strategy for separator modification towards building a much-anticipated dendrite-free Li anode and realizing long-lifespan lithium metal batteries.

Rare-earth praseodymium-substituted Bi5Ti3FeO15 exhibiting enhanced piezoelectric properties for high-temperature application

Owing to their exceptional piezoelectric effects, piezoelectric materials play a crucial role in high-end technologies and contribute significantly to the national economy. Bismuth layer-structured ferroelectrics (BLSFs) possess high Curie temperatures, making them a focal point of research in high-temperature piezoelectric sensor devices. However, their poor piezoelectric performance and low direct-current (DC) electrical resistivity hinder their effective deployment in high-temperature applications. To overcome these shortcomings, we employed composition optimization by partially substituting bismuth ions with rare-earth praseodymium ions. This approach enhances the piezoelectric performance and improves the DC electrical resistivity by preventing the loss of volatile bismuth ions and stabilizing the bismuth oxide layer (Bi2O2)2+, thereby reducing the concentration of oxygen vacancies. Consequently, we achieved a large piezoelectric constant d33 of 23.5 pC/N in praseodymium-substituted Bi5Ti3FeO15, which is three times higher than that of pure Bi5Ti3FeO15 (7.1 pC/N), along with a high Curie temperature TC of 778 °C. Additionally, the optimal composition of 4 mol% praseodymium-substituted Bi5Ti3FeO15 exhibits good thermal stability of electromechanical coupling characteristics up to 300 °C. This study holds promise for a wide array of high-temperature piezoelectric applications and has the potential to accelerate the development of high-temperature piezoelectric sensor technologies.

Giant tunnelling electroresistance in atomic-scale ferroelectric tunnel junctions

Ferroelectric tunnel junctions are promising towards high-reliability and low-power non-volatile memories and computing devices. Yet it is challenging to maintain a high tunnelling electroresistance when the ferroelectric layer is thinned down towards atomic scale because of the ferroelectric structural instability and large depolarization field. Here we report ferroelectric tunnel junctions based on samarium-substituted layered bismuth oxide, which can maintain tunnelling electroresistance of 7 × 105 with the samarium-substituted bismuth oxide film down to one nanometer, three orders of magnitude higher than previous reports with such thickness, owing to efficient barrier modulation by the large ferroelectric polarization. These ferroelectric tunnel junctions demonstrate up to 32 resistance states without any write-verify technique, high endurance (over 5 × 109), high linearity of conductance modulation, and long retention time (10 years). Furthermore, tunnelling electroresistance over 109 is achieved in ferroelectric tunnel junctions with 4.6-nanometer samarium-substituted bismuth oxide layer, which is higher than commercial flash memories. The results show high potential towards multi-level and reliable non-volatile memories.

Structure, Electrical Properties, and Thermal Stability of the Mn/Nb Co-Doped Aurivillius-Type Na0.5Bi4.5Ti4O15 High Temperature Piezoelectric Ceramics

In order to meet the urgent need for high temperature piezoelectric materials with a Curie temperature over 400 °C, the Mn/Nb co-doped strategy has been proposed to improve the weak piezoelectric performance of the Aurivillius-type Na0.5Bi4.5Ti4O15 (NBT) high temperature piezoelectric ceramics. In this paper, the crystal structure, electrical properties, and thermal stability of the B-site Mn/Nb co-doped Na0.5Bi4.5Ti4-x(Mn1/3Nb2/3)xO15 (NBT-100x) ceramics were systematically investigated by the conventional solid-state reaction method. The crystal structural analysis results indicate that the NBT-100x ceramics have typical bismuth oxide layer type phase structure and high anisotropic plate-like morphology. The lattice parameters and the grain sizes increase with the B-site Mn/Nb co-doped content. The electrical properties were significantly improved by Mn/Nb co-doped modifications. The maximum of the piezoelectric coefficient d33 was found to be 29 pC/N for the NBT-2 ceramics, nearly twice that of the unmodified NBT ceramics. The highest values of the planar electromechanical coupling factor kp and thickness electromechanical coupling factor kt were also obtained for the NBT-2 ceramics, at 5.4% and 31.2%, respectively. The dielectric spectroscopy showed that the Curie temperature Tc of the Mn/Nb co-doped NBT-100x ceramics is slightly higher than that of unmodified NBT ceramics (646 °C). The DC resistivity of the NBT-2 ceramics is higher than 106 Ω∙cm at 500 °C. All the results together with the good thermal stability demonstrated the Mn/Nb co-doped ceramics as an effective method to improve the NBT based piezoelectric ceramics and the potential candidates of the Mn/Nb co-doped NBT-100x ceramics for high temperature piezoelectric applications.

Bismuth oxide modifies titanium implant for improved osteogenesis and immune regulation

Aseptic loosening often leads to orthopedic implantation failure. In this study, to improve the osteointegration of Ti orthopedic implants, bismuth oxide (Bi2O3) layer was magnetron sputtering coated on Ti surface. The Bi2O3 coating had few influence on the surface morphology and wettability of Ti. In vitro cell culture of rat bone marrow stem cells (rBMSCs) suggested that Bi2O3 coating showed good cytocompatibility and was favorable for its osteogenic differentiation. Furthermore, the Bi2O3 coating was found to induce macrophage cells (RAW264.7) polarize to anti-inflammatory phenotype, whereas inhibit its pro-inflammatory polarization. With improved osteogenesis and tissue repair immune regulation, the designed Bi2O3 coating is promising for orthopedic applications.

Atomistic Simulation of La and Mn-Doped PbBi2Nb2O9 Aurivillius Phase

This study aims to determine the effect of Mn3+ and La3+ dopants on the structure of PbBi2Nb2O9 (PBN) using atomistic simulation. PBN phase geometry was optimized before the Mn3+ and La3+-doped phase. Mn3+ partially substituted octahedral Nb5+ in the perovskite layer. While La3+partially substituted Bi3+ in the bismuth layer and dodecahedral Pb2+in the perovskite layer. The concentration (x) of dopants that doped PBN was made in such a way that it produces a phase of Pb1-2xBi1.5 + 2xLa0.5Nb2-xMnxO9 (x = 0, 0.1, and 0.3) which was not charged. The simulation results showed that the optimized PBN cell parameters were in a good agreement with the experimental result. Increasing the concentration of dopants result in the Pb1-2xBi1.5+ 2xLa0.5Nb2-xMnxO9 phase (PBNM-Bi and PBNM-A) being less stable, as indicated by the increased lattice energy. PBNLM-Bi structures experiences an elongation which was showed by the cell parameters of c increase while a and b decrease. La3+prefers to occupy bismuth oxide layer rather than the dodecahedral A-site of the perovskite layer. The results of this simulation can explain the PBLNM structure of experimental results that do not pay attention to the multiplicity of doped PBN with certain dopant concentrations.

Spin Hall Effect in Bilayer Graphene Combined with an Insulator up to Room Temperature.

Spin-orbit coupling in graphene can be enhanced by chemical functionalization, adatom decoration, or proximity with a van der Waals material. As it is expected that such enhancement gives rise to a sizable spin Hall effect, a spin-to-charge current conversion phenomenon of technological relevance, it has sparked wide research interest. However, it has only been measured in graphene/transition-metal dichalcogenide van der Waals heterostructures with limited scalability. Here, we experimentally demonstrate the spin Hall effect up to room temperature in graphene combined with a nonmagnetic insulator, an evaporated bismuth oxide layer. The measured spin Hall effect arises most likely from an extrinsic mechanism. With a large spin-to-charge conversion efficiency, scalability, and ease of integration to electronic devices, we show a promising material heterostructure suitable for spin-based device applications.

Bi2W2O9: A potentially antiferroelectric Aurivillius phase

Ferroelectric tungsten-based Aurivillius oxides are naturally stable superlattice structures, in which A-site deficient perovskite blocks [WnO3n+1]-2 (n = 1, 2, 3, ...) interleave with fluorite-like bismuth oxide layers [Bi2O2]+2 along the c -axis. In the n = 2 Bi2W2O9 phase, an in-plane antipolar distortion dominates but there has been controversy as to the ground state symmetry. Here we show, using a combination of first-principles density functional theory calculations and experiments, that the ground state is a non-polar phase of Pnab symmetry. We explore the energetics of metastable phases and the potential for antiferroelectricity in this n=2 Aurivillius phase.

Electrical and Raman Spectroscopic Studies on Aurivillius Layered-Pervoskite Ceramics

Double rare-earth (La; Sm/Gd) substituted Aurivillius family of Bismuth Layered Structured Ferroelectrics (BLSF) namely Bi2.6Sm0.2La0.2TiNbO9 (BSLT; sample-A), Bi2.6Gd0.2La0.2TiNbO9 (BGLT; sample-B), single phase ceramics were prepared by solid state route. In addition, intergrowth (x BSLT - (1-x) BGLT, where x=0.49; sample-C) and solid solution (BSLT­x - BGLTy; where x + y=0.4; sample-D) materials were prepared. Dielectric, ferroelectric and Raman spectroscopic properties were studied on the said above materials. The X-ray diffraction analysis and Raman spectra revealed well-formation of stable structure. Though, the sample-C and sample-D have lower coercive field, compared to the sample-A and sample-B, but they exhibited sharp hysterisis loop. Therefore the instrinsic defects of sample-D inhabits more sensitivity towards the ferroelectric behaviour. The results were corroborated to the impedance and dielectrical data. The results were consistent with the SEM micrographs and complex impedance plots. An attempt is made to understand the effect of rare-earth ions on A-site of layered-pervoskite structure, defined as: (Bi2O2)2+(An-1BnO3n+1)2-.The term n represents number of pervoskite blocks interleaved with the bismuth oxide layers.

Exploration of New Birefringent Crystals in Bismuth d0 Transition Metal Selenites.

The first examples of bismuth fluoride selenites with d0 -TM/TeVI polyhedrons, namely, Bi4 TiO2 F4 (SeO3 )4 (1), Bi4 NbO3 F3 (SeO3 )4 (2), Bi4 TeO4 F2 (TeO3 )2 (SeO3 )2 (3), Bi2 F2 (MoO4 )(SeO3 ) (4) and Bi2 ZrO2 F2 (SeO3 )2 (5) have been successfully synthesized under hydrothermal reactions by aliovalent substitution. The five new compounds feature three different types of structures. Compounds 1-3, containing TiIV , NbV and TeVI respectively, are isostructural, exhibiting a new 3D framework composed of a 3D bismuth oxyfluoride architecture, with intersecting tunnels occupied by d0 -TM/TeVI octahedrons and selenite/tellurite groups. Interestingly, compound Bi4 TeO4 F2 (TeO3 )2 (SeO3 )2 (3) is the first structure containing SeIV and mixed-valent TeIV /TeVI cations simultaneously. Compound 4 features a new 3D structure formed by a 3D bismuth oxyfluoride network with MoO4 tetrahedrons and selenites groups imbedded in the 1D tunnels. Compound 5 displays a novel pillar-layered 3D open framework, consisting of 2D bismuth oxide layers bridged by the [ZrO2 F2 (SeO3 )2 ]6- polyanions. Theoretical calculations revealed that the five compounds displayed very strong birefringence. The birefringence values of compounds 1-3, especially, are above 0.19 at 1064 nm, which are larger than the mineral calcite. Based on the structure and property analysis, it was found that the asymmetric SeO3 groups (and TeO3 in compound 3) displayed the largest anisotropy, compared with the bismuth cations and the d0 -TM/Te polyhedra, which is beneficial to the birefringence.

Characterization of Bi2O3/ZnS heterojunctions designed for visible light communications

In the current work, the structural, morphological and optical properties of the Bi2O3/ZnS heterojunctions as visible light communication (VLC) technology element are explored. Bismuth oxide layers of thicknesses of 200 nm are used as substrate to evaporate ZnS films of thicknesses of 500 nm by the thermal evaporation technique under vacuum pressure of 10−5 mbar. The heterojunction devices are studied by the x-ray diffraction, scanning electron microscopy, optical spectrophotometry and microwave spectroscopy techniques. The Bi2O3/ZnS heterojunctions are found to form a highly strained structure with extremely large lattice mismatches. By the strained structure and with the valence and conduction band offsets that exhibit values of 1.04 and 0.41 eV, respectively, it was possible to enhance the light absorbability of ZnS by 459 times at 3.10 eV. In addition, the dielectric constant spectra of the device display a linear and nonlinear optical properties below and above 1.94 eV, respectively. Moreover, the optical conductivity parameters including the drift mobility and plasmon frequency and the cutoff frequency spectra of an area of 0.50 cm2 of Bi2O3/ZnS interfaces have shown the ability of using these heterojunction devices as light signal receivers that attenuate signals at terahertz frequencies in the range of 0.27–1.00 THz. As an additional demonstration, the Bi2O3/ZnS heterojunction devices were subjected to a microwave signal propagation in the frequency domain of 0.01–2.90 GHz. The device performed as band filters at gigahertz frequencies.

Activation of the Highly‐Selective Pd11Bi2Se2 during the Semi‐Hydrogenation of Acetylene

Pd11Bi2Se2 was prepared as single‐phase material and used in an unsupported state as catalyst in the semi‐hydrogenation of acetylene in ethylene excess. After an initial inactive time‐period, Pd11Bi2Se2 activated and showed high acetylene conversion and selectivity towards ethylene at 473 K. In addition, after the initial inactive state, the compound revealed high stability during 100 h time on stream. At 80 % conversion the selectivity to ethylene is higher than 90 %. Post‐catalysis investigations by powder X‐ray diffraction (p‐XRD) and X‐ray photoelectron spectroscopy (XPS) exclude the formation of intermetallic hydrides, decomposition, and the presence of elemental palladium. Furthermore, comparison of XPS before and after catalysis revealed the reason of the inactive state of the intermetallic compound during the first hours of catalysis. An initial surface layer of bismuth oxide is reduced and re‐incorporated into the intermetallic compound. This material change is responsible for the initially observed activation of Pd11Bi2Se2 during the semi‐hydrogenation of acetylene.

Ion Doping Effects on the Lattice Distortion and Interlayer Mismatch of Aurivillius-Type Bismuth Titanate Compounds.

Taking Bismuth Titanate (Bi4Ti3O12) as a Aurivillius-type compound with m = 3 for example, the ion (W6+/Cr3+) doping effect on the lattice distortion and interlayer mismatch of Bi4Ti3O12 structure were investigated by stress analysis, based on an elastic model. Since oxygen-octahedron rotates in the ab-plane, and inclines away from the c-axis, a lattice model for describing the status change of oxygen-octahedron was built according to the substituting mechanism of W6+/Cr3+ for Ti4+, which was used to investigate the variation of orthorhombic distortion degree (a/b) of Bi4Ti3O12 with the doping content. The analysis shows that the incorporation of W6+/Cr3+ into Bi4Ti3O12 tends to relieve the distortion of pseudo-perovskite layer, which also helps it to become more stiff. Since the bismuth-oxide layer expands while the pseudo-perovskite layer tightens, an analytic model for the plane stress distribution in the crystal lattice of Bi4Ti3O12 was developed from the constitutive relationship of alternating layer structure. The calculations reveal that the structural mismatch of Bi4Ti3O12 is constrained in the ab-plane of a unit cell, since both the interlayer mismatch degree and the total strain energy vary with the doping content in a similar trend to the lattice parameters of ab-plane.

친환경 차폐물질을 이용한 이중구조 차폐체의 설계

Recently, a barium(Ba) and an iodine(I) being studied as a conventional lead(Pb) alternatives of shielding material has excellent shieding rate, but the characteristic x-ray photons in the energy range near 30 keV line is released. In this study, with bismuth oxide(BiO) coupled barium sulfate(BaSO4) double layer, transmitted spectra, shieding rates and relative weighting rates were evaluated to validate the applicability of eco-friendly double layer shieding structure using monte carlo simulations as a prior study. From the evaluation results, in 0.4mm and 0.5mm thickness of BiO layers coupled with top 0.1mm-BaSO4 layer, the shieding rate showed 1.9% and 3.9% higher than 0.6mm thickness of Pb single layer, respectively. In addition, the relative weight also 28% and 34.5% lower than 0.6mm-Pb in 0.4mm and 0.5mm thickness of BiO layers coupled with top 0.1mm-BaSO4 layer.

Bismuth iron oxide thin films using atomic layer deposition of alternating bismuth oxide and iron oxide layers

Bismuth iron oxide films with varying contributions from Fe2O3 or Bi2O3 were prepared using atomic layer deposition. Bismuth (III) 2,3-dimethyl-2-butoxide, was used as the bismuth source, iron(III) tert-butoxide as the iron source and water vapor as the oxygen source. The films were deposited as stacks of alternate Bi2O3 and Fe2O3 layers. Films grown at 140°C to the thickness of 200–220nm were amorphous, but crystallized upon post-deposition annealing at 500°C in nitrogen. Annealing of films with intermittent bismuth and iron oxide layers grown to different thicknesses influenced their surface morphology, crystal structure, composition, electrical and magnetic properties. Implications of multiferroic performance were recognized in the films with the remanent charge polarization varying from 1 to 5μC/cm2 and magnetic coercivity varying from a few up to 8000A/m.

Tribochemistry of Bismuth and Bismuth Salts for Solid Lubrication.

One of the main trends in the past decades is the reduction of wastage and the replacement of toxic compounds in industrial processes. Some soft metallic particles can be used as nontoxic solid lubricants in high-temperature processes. The behavior of bismuth metal particles, bismuth sulfide (Bi2S3), bismuth sulfate (Bi2(SO4)3), and bismuth oxide (Bi2O3) as powder lubricants was studied in a range of temperatures up to 580 °C. The mechanical behavior was examined using a high-temperature pin-on-disc setup, with which the friction force between two flat-contact surfaces was recorded. The bismuth-lubricated surfaces showed low coefficients of friction (μ ≈ 0.08) below 200 °C. Above the melting temperature of the metal powder at 271 °C, a layer of bismuth oxide developed and the friction coefficient increased. Bismuth oxide showed higher friction coefficients at all temperatures. Bismuth sulfide exhibited partial oxidation upon heating but the friction coefficient decreased to μ ≈ 0.15 above 500 °C, with the formation of bismuth oxide-sulfate, while some bismuth sulfate remained. All surfaces were studied by X-ray diffraction (XRD), confocal microscopy, high-resolution scanning electron microscopy (HR-SEM), and energy-dispersive X-ray spectroscopy (EDS). This study reveals how the partial oxidation of bismuth compounds at high temperatures affects their lubrication properties, depending on the nature of the bismuth compound.

Growth of the Bi2Se3 Surface Oxide for Metal–Semiconductor–Metal Device Applications

The effect of the surface structure of Bi2Se3 on its interior properties has been well studied recently, but the interfacial structure and electrical properties of the oxidized Bi2Se3 surface are little known. In contrast to the self-limited formation of native oxide on Bi2Se3, the degree of oxidation on the Bi2Se3 surface in oxygen plasma is enhanced. Results of transmission electron microscopy and X-ray photoelectron spectroscopy show that the surface of the oxidized Bi2Se3 is composed of a layer of amorphous bismuth oxide (BiOx), and the thickness of the BiOx layer can be controlled by the length of the plasma process. Electrical measurements of this structure present the Schottky-type transport property at the interface between the oxidized layer and the bulk Bi2Se3 crystal, and the turn-on voltage depends on the thickness of the surface BiOx layer. This study of the structure, formation mechanism, and electrical properties of the surface oxide of Bi2Se3 formed in oxygen plasma provides useful informa...

Enhanced Performance of β-Bi2O3 by In-Situ Photo-Conversion to Bi2O3-BiO2-x Composite Photoanode for Solar Water Splitting

Ordered nanoporous bismuth oxide layer consisting of metastable β-Bi2O3 phase that showed n-type semiconductivity was synthesized by a simple electrochemical anodization of bismuth substrate. When the anodic nanoporous β-Bi2O3 samples were tested as photoanodes for solar water splitting application in 0.5 M Na2SO4 (pH:5.8), and 1 M KOH (pH:13.7), the photocurrent decayed continuously with time from an initial value of 0.95 mA/cm2 under 1-sun illumination at a bias potential of 1.5 VRHE. Accumulation of photo generated holes at the photoanode/ electrolyte was attributed to the photocurrent decay. Addition of methanol as sacrificial hole scavenger was not found to be effective for the bismuth oxide photoanodes. When hydrogen peroxide was added to the 0.5 M Na2SO4 electrolyte, the photocurrent density increased to ∼4 mA/cm2 and was stable for more than 1 h of illumination of AM1.5 global light at 1.5 VRHE. Addition of hydrogen peroxide to the 1 M KOH solution showed a gradual increase in the photocurrent density for the first 300 seconds of light illumination to a maximum value of ∼10 mA/cm2 at 0.65 VRHE and then it decreased continuously. The high photocurrent density of nanoporous β-Bi2O3 in 1 M KOH + 0.3 M H2O2 was be attributed to the presence of photo-converted Bi2O4-x phase which harvested more light in the visible wavelengths.

Interlayer Communication in Aurivillius Vanadate to Enable Defect Structures and Charge Ordering.

The fluorite-like [Bi2O2](2+) layer is a fundamental building unit in a great variety of layered compounds. Here in this contribution, we presented a comprehensive study on an unusual Aurivillius phase Bi3.6V2O10 with respect to its defect chemistry and polymorphism control as well as implications for fast oxide ion transport at lower temperatures. The bismuth oxide layer in Bi4V2O11 is found to tolerate a large number of Bi vacancies without breaking the high temperature prototype I4/mmm structure (γ-phase). On cooling, an orthorhombic distortion occurs to the γ-phase, giving rise to a different type of phase (B-phase) in the intermediate temperature region. Cooling to room temperature causes a further transition to an oxygen-vacancy ordered A-phase, which is accompanied by the charge ordering of V(4+) and V(5+) cations, providing magnetic (d(1)) and nonmagnetic (d(0)) chains along the a axis. This is a novel charge ordering transition in terms of the concomitant change of oxygen coordination. Interestingly, upon quenching, both the γ- and B-phase can be kinetically trapped, enabling the structural probing of the two phases at ambient temperature. Driven by the thermodynamic forces, the oxide anion in the γ-phase undergoes an interlayer diffusion process to reshuffle the compositions of both Bi-O and V-O layers.

Effect of time and temperature on TLP bonding of alumina using a bismuth oxide interlayer

The present study investigated transient liquid phase (TLP) bonding of alumina (Al2O3) ceramics. A thin layer of bismuth oxide (Bi2O3) was placed as an interlayer between the alumina bodies. Alumina samples were bonded at 850, 900, 950, 1000, and 1050°C for various holding times to study the effect of time and temperature on the morphology and microstructure of the interfacial area. The microstructure of the joints was examined using scanning electron microscopy equipped with an energy dispersive spectrometer. To identify the phases that develop during bonding, X-ray diffraction was performed over the fracture surfaces. The mechanical properties of the joined specimens were examined using a shear testing method. The results showed that increasing the time and temperature resulted in bismuth oxide diffusion into alumina, forming Al2Bi24O39, AlBiO3, and Al2Bi4O9 compounds. At temperatures above 1000°C, voids appeared in the interface because all phases transformed into Al4Bi2O9 compound. The highest joint strength of about 73MPa was obtained for the sample joined at 900°C for a holding time of 12h.