Bi-2212 Phase Research Articles

Underpotential deposition of SnBi thin films for sodium ion batteries: The effect of deposition potential and Sn concentration

Bimetallic SnBi film was deposited on a Cu foil substrate via the electrochemical atomic layer deposition (E-ALD) technique. The deposition attainment of Sn and Bi were investigated using cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The deposition potential of Bi was varied in the underpotential deposition (UPD) region and the concentration of Sn was varied in the SnBi bimetallic material. The materials were characterised using field emission scanning electron microscopy coupled with energy dispersive spectroscopy (FE-SEM/EDS) for morphology and elemental distribution, focused ion beam scanning electron microscopy (FIBSEM) for thickness, X-ray diffraction (XRD) for crystallinity and inductively coupled plasma mass spectroscopy (ICP-MS) for composition measurements. Bi deposited at different UPD regions was structurally different. The deposits were crystalline SnBi materials containing Sn, Bi and other phases of Cu and Sn. Bi was concentrated on the surface, while Sn was distributed evenly across the film. The SnBi electrodes were tested as anode materials in Na-ion batteries using galvanostatic cycling (GC), CV and electrochemical impedance spectroscopy (EIS). Initial discharge capacities of 1900 mAh g−1 for SnBi (1:1) and 341 mAh g−1 for SnBi (3:1) electrodes at 38.5 mA g−1 were obtained, while the electrodes suffered capacity loss after 10 cycles.

Wettability, Interfacial Behavior and Joint Properties of Sn-15Bi Solder

Sn-15Bi solid solution solder provides a potential replacement for Sn-40Pb solder due to lower cost and similar melting point. Sn-15Bi solder was compared with Sn-40Pb solder to assess the microstructure, wettability, bulk tensile properties, interfacial microstructures in solder joints with a Cu substrate, the interfacial evolution in joints during isothermal aging, and the shear strength on ball solder joints with the effect of aging conditions. The microstructure of Sn-15Bi bulk solder was composed of the primary β-Sn phase with Bi in solid solution and with precipitated Bi phases along the grain boundaries. The wettability of solder alloys was evaluated with wetting balance testing, and the results showed that Sn-15Bi solder had a lower wetting force and longer wetting time than Sn-40Pb solder. The poorer wettability of Sn-15Bi solder was not influenced by different types of soldering flux, but improved with increasing temperature. Tensile tests on bulk solder alloys indicated that Sn-15Bi solder had a higher tensile strength but lower elongation than Sn-40Pb solder. Also, the tensile strength of Sn-Bi solder decreased with decreasing strain rate and with increasing temperature, while the elongation of Sn-Bi solder was independent of the temperature and strain rate. In as-soldered joints, Sn-15Bi solder produced a thicker Cu6Sn5 layer than Sn-40Pb solder. Following isothermal aging, the thickness of the interfacial Cu-Sn intermetallic compound (IMC) increased with the aging time, and the growth rate of the IMC layer in Sn-15Bi solder joints was slightly higher than that in Sn-40Pb solder joints during aging. Ball shear test on solder joints illustrated that Sn-15Bi solder joint had a higher shear strength than Sn-40Pb solder joint, and that with increased aging time, the solder became stronger due to precipitation of Bi, leading to a change in the fracture mode from ductile failure in the solder to brittle fracture at the IMC interface.

Stability of ferroelectric phases and magnetoelectric response in multiferroic (1-x)Bi(Ni1/2Ti1/2)O3-PbTiO3/xNi0.6Zn0.4Fe2O4 particulate composites

Multiferroic particulate composites have been fabricated by taking the morphotropic phase boundary composition of ferroelectric phase Bi(Ni1/2Ti1/2)O3–PbTiO3 and magnetic phase (Ni,Zn)Fe2O4. The ferroelectric phase has coexisting monoclinic and tetragonal perovskite structures with space group Pm and P4mm, respectively whereas the magnetic phase has spinel cubic structure with space group Fd3‾m. Rietveld structural analysis for the each components of composite reveals that the tetragonality (c/a) of the ferroelectric phase continuously increases with increasing the concentration of magnetic phase and finally transform in rhombohedral (R3‾c) phase suggesting partial ionic diffusion between ferroelectric and magnetic phases. Composition dependent Mössbauer spectra of (1-x)Bi(Ni1/2Ti1/2)O3–PbTiO3/x(Ni,Zn)Fe2O4 reveals the superparamagnetic like behavior for the ferroelectric rich composition with x = 0.2. The magnetic ordering increases for the composition with x = 0.4 and 0.6 which completely transforms into ferrimagnetic for the composition with x = 0.9. Unlike the ferroelectric or magnetic components that do not exhibit the magnetoelectric response separately, significant value of magnetoelectric coefficient (> 30 mV/Oe-cm) in (1-x)Bi(Ni1/2Ti1/2)O3–PbTiO3/xNi0.6Zn0.4Fe2O4 composite makes it promising for multifunctional applications.

Superconducting joint interface for multi-filamentary Bi2223 tapes fabricated by JIM method

Recently, we proposed a method of joint by incongruent melting (JIM) for making a superconducting connection between two multi-filamentary Bi2223 tapes. At high temperatures, the Bi2223 phase separates into solid Bi2212 and a liquid phase by incongruent melting. In the JIM method, the Bi2223 filaments in a tape are first melted to Bi2212 and liquid. Then, Bi2212 is connected by the liquid to form a superconducting current pathway. In the present experiment, a joint between multi-filamentary Bi2223 tapes was prepared, resulting in a superconducting joint with a critical current of 8 A at 77 K. We then investigated the microstructure of the superconducting joint interface using X-ray diffraction and SEM/EDS, to clarify the superconducting joint formation. In examining samples prepared using the JIM method, Bi2212 and Sr-Ca-Cu-O system compounds were found at the joint interface, which had a high crystalline orientation.

Effect of nano-sized metallic Au additions at large scale on the phase stability of Bi-2212 ceramics

Bi1.8Sr2AuxCa1.1Cu2.1Oy (Bi-2212) polycrystalline ceramics with x = 0.25, 0.3 and 0.35 have been prepared by the solid-state reaction method. XRD results showed the Bi-2212 phase as the major one in all samples, accompanied by metallic Au, and some secondary phases such as Bi2CaO4. Tc values are very similar for all samples, indicating that the carrier concentration is independent of the amount of Au. Magnetic properties of samples, determined through magnetic hysteresis measurements (M–H) performed at both T = 2 and 10 K, showed that samples maintain their diamagnetic characteristics in all cases. In addition, Jc values, calculated from their magnetic hysteresis loops using the Bean’s model, showed that addition of metallic Au in high contents leads to an important increase when compared to the samples with low Au content.

Possible two-component pairings in electron-doped Bi2Se3 based on a tight-binding model

Recent experiments show the spontaneous breaking of rotational symmetry in the superconducting topological insulators M$_{x}$Bi$_{2}$Se$_{3}$ (M represents Cu, Sr, or Nd), suggesting that the pairing belongs to a two-dimensional representation of the $D_{3d}$ symmetry group of the crystal. Motivated by these progresses, we construct an exhaustive list of possible two-component pairings of the M$_{x}$Bi$_{2}$Se$_{3}$ superconductors, both for the odd-parity $E_{u}$ representation and for the even-parity $E_{g}$ representation. Starting from a tight-binding model for the normal phase of Bi$_{2}$Se$_{3}$ and M$_{x}$Bi$_{2}$Se$_{3}$, we firstly construct the pairing channels in the spin-orbital basis, up to second-nearest-neighbor pairing correlations in the basal plane. We then infer the properties of these pairings by transforming them to the band (pseudospin) basis for the conduction band. A comparison with the key experimental consensuses on M$_{x}$Bi$_{2}$Se$_{3}$ superconductors shows that the true pairings should also be multichannel. Besides a nematic and time-reversal symmetric pairing combination, the other pairings that we have identified are chiral and nematic at the same time, which may be nonunitary and have a spontaneous magnetization. A complementary set of experiments are proposed to identify the true pairing symmetries of these superconductors and their evolution with the doping concentration $x$.

Structural, superconducting and vortex pinning properties of Nb-substituted Bi-2212 ceramic superconductor

In this research, we have deeply focused to investigate the effects of Niobium (Nb) substitution for the Ca site in the Bi2Sr2Ca1−xNbxCu2O8+y superconductors with x = 0.00, 0.05, 0.10, 0.20, 0.30, and 0.40. The materials were synthesized via well-known solid state reaction method. We have performed X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and dc magnetization measurements in order to understand the effects of Nb-content. XRD results exhibit that the Bi-2212 phase is a major phase for pure sample. On the other hand, the volume fraction of Bi-2212 declines with increasing Nb substitution and relocates with low-Tc phase, namely Bi-2201. The maximum pinning force, FPmax, values of x = 0.05 and 0.10 Nb-substituted samples are improved in comparison to the pure sample. These values are found as 5.18 × 107 and 5.21 × 107 Oe A/cm2 at T = 10 K for x = 0.05 and 0.10 Nb-substituted sample, respectively, which are higher than the 4.92 × 107 Oe A/cm2 value of the pure sample.

Impact of gamma and electron irradiations on superconducting properties of Bi1.6Pb0.4Sr2Ca2Cu3O10 (Bi-2223) superconductor

In several studies on the impact of radiation towards superconductor, there were evidences that changes may occur in superconducting properties due to alteration in lattice structure of HTS materials. In this work, the solid-state reaction method was employed in preparing the bulk samples of Bi1.6 Pb0.4Sr2Ca2Cu3O10 (hereafter Bi-2223) superconductor. The samples were then irradiated with gamma and electron sources with dosage of 100 kGray each. X-ray powder diffraction (XRD) patterns were used to determine the phases that present in the samples. Results of XRD patterns for both the non-irradiated and irradiated samples showed well-defined peaks all of which could be indexed based on the Bi-2223 phase structure. Besides, the XRD patterns indicate that gamma and electron irradiations did not affect the Bi-2223 superconducting phase structure. Measurements of the critical temperature, TC and the critical current density, JC of all the samples were conducted before and after irradiation using AC susceptibility technique. TC for non-irradiated, electron irradiated and gamma irradiated sample is 97 K, 95 K and 103 K, respectively. On the other hand the JC for non-irradiated, electron irradiated and gamma irradiated sample is 1618 A/cm2 1729 A/cm2 and 1549 A/cm2 respectively. Results of scanning electron microscopy (SEM) micrographs show improvement in the grain growth and disorientation in the texture of all the gamma and electron irradiated samples.

The Origins of Trypillia Megasites

The Trypillia megasites of Ukraine are the largest known settlements in 4th millennium BC Europe and possibly the world. With the largest reaching 320ha in size, megasites pose a serious question about the origins of such massive agglomerations. Most current solutions assume maximum occupation, with all houses occupied at the same time, and target defence against other agglomerations as the cause of their formation. However, recent alternative views of megasites posit smaller long-term occupations or seasonal assembly places, creating a settlement rather than military perspective on origins. Shukurov et al. (2015)'s model of Trypillia arable land-use demonstrates that subsistence stresses begin when site size exceeded 35ha. Over half of the sites dated to the Trypillia BI stage - the stage before the first megasites - were larger than 35ha, suggesting that some form of buffering involving exchange of goods for food was in operation. There were two settlement responses to buffering:- clustering of sites with enhanced inter-site exchange networks and the creation of megasites. The trend to increased site clustering can be seen from Phase BI to CI, coeval with the emergence of megasites. We can therefore re-focus the issue of origins on why create megasites in site clusters. In this article, we discuss the two strategies in terms of informal network analysis and suggest reasons why, in some cases, megasites developed in certain site clusters. Finally, we consider the question of whether Trypillia megasites can be considered as 'cities'.

Ferrimagnetic Cr2S3 effects on (Bi1.6Pb0.4)Sr2CaCu2O8 superconductor

The interaction between superconductivity and magnetism is an interesting topic because of the mutually exclusive nature. In this paper, we report ferrimagnetic Cr2S3 effects on (Bi1.6Pb0.4)Sr2CaCu2O8 (Bi2212) superconductor with nominal starting composition Bi2212(Cr2S3)x (x = 0–0.20 wt%). The Curie temperature of Cr2S3 is 120 K and this is much higher than the transition temperature of Bi-2212 phase (~ 81 K). X-ray diffraction (XRD) patterns showed that the Bi-2212 phase was the dominant in all samples. The x = 0.2 XRD pattern showed the formation of a glassy phase. Field emission scanning electron microscopy (FESEM) showed an improvement in the layered-like microstructure with increasing Cr2S3 content. The non-added sample showed the highest zero-resistance temperature, Tc-zero and onset temperature, Tc-onset at 81 K and 69 K, respectively. Addition of Cr2S3 decreased the transition temperature. The peak temperature, Tp of the imaginary part of the AC susceptibility χ′′ decreased with Cr2S3 addition indicating that the flux pinning capability of the Bi-2212 phase was suppressed. The results were explained in terms mutually exclusive nature of superconductivity and magnetism.

Effect of Cesium Substitution on the Superconducting Properties of Bi-2212 Samples Prepared Via Solid-State Reaction and Laser Floating Zone Technique

In this work, the effect of cesium substitution on the structural and superconducting properties of Bi2Sr2Ca1-xCsxCu2O+y (where x = 0.0, 0.025, 0.050, 0.075, 0.10, 0.125, and 0.15) samples prepared by the solid-state reaction route and by directional growth using the laser floating zone (LFZ) technique has been studied. X-ray diffraction has shown that both kinds of samples present the 2212 phase as the major one, with pseudo tetragonal structure, accompanied by minor amounts of (Sr,Ca)CuO2 and Bi2(Sr,Ca)4O6 + d secondary phases. SEM-EDX results indicate that Bi-2212 phase is the major one, with small amounts of secondary phases. Cs substitution diminishes the size and content of secondary phases. Magnetization measurements reflect different behavior for sintered and LFZ grown samples. Although the diamagnetic transition is very wide for the former samples, it is very sharp for the last ones. The critical onset temperatures, TC, are around 80 and 90 K, for sintered and LFZ grown samples, respectively. Moreover, M–H measurements indicate that LFZ grown samples exhibit larger areas than the sintered ones. The intragranular critical current, JC, calculated from the M–H loops and Bean’s formula, is maximum for x = 0.025Cs sintered and x = 0.05Cs LFZ grown samples. The maximum pinning forces, FPmax, determined in these samples are higher than those obtained in undoped ones, reaching 9 × 107 Oe*A/cm2 and 10 × 108 Oe*A/cm2, at 10 K, for sintered and LFZ grown samples, respectively.

Bismuth thickness-dependent structural and electronic properties of Bi/As2Se3 bilayer thin films

The structural, microstructural and electronic band gap properties of bilayer Bi/As2Se3 thin films prepared on glass substrate have been discussed in detail. The thin films prepared by thermal evaporation technique under high vacuum were characterized by X-ray diffraction (XRD), Raman spectroscopy, field-emission scanning electron microscopy (FESEM) and UV–visible–NIR spectrophotometer. The bilayer films with small Bi thickness showed amorphous nature, while large Bi thickness film led to the development of sharp XRD peaks corresponding to Bi and Bi2Se3 phase. The band gap of the studied film decreased with increasing Bi layer thickness which is explained on the basis of high concentration of localized defect states in the band gap region. The FESEM images showed the smooth and homogeneous surface for all the films. The Raman spectra showed the different structural units like AsSe3 pyramidal unit and Se8 rings that change with the Bi layer thickness. The present study reveals the interface diffusion of Bi into As2Se3 layer and interaction of Bi with Se due to exposure of the films to UV radiation.

Magneto‐Optical Bi:YIG Films with High Figure of Merit for Nonreciprocal Photonics

AbstractThin film magneto‐optical (MO) materials are enablers for integrated nonreciprocal photonic devices such as isolators and circulators. Films of polycrystalline bismuth‐substituted yttrium iron garnet (Bi:YIG) have been grown on silicon substrates and waveguide devices, in which an yttrium iron garnet (YIG) seedlayer is placed either above or below the active Bi:YIG layer to promote crystallization. The films exhibit a high MO figure of merit of up to 769° dB−1 at 1550 nm wavelength. Growth of single phase Bi:YIG on the sidewalls of waveguides is demonstrated, which can be used in nonreciprocal transverse electric (TE)‐mode devices.

Microstructure, improved magnetic properties, and recoil loops characteristics for MnBi alloys

Abstract MnBi is a potential candidate for permanent magnets that can be used in high-temperature applications due to the large magnetocrystalline anisotropy and unique positive temperature coefficient of coercivity. In this work, MnBi magnets with a high content of low temperature phase (LTP) were prepared by arc melting followed by heat treatment. The high coercivity of 7.11 kOe at 300 K and 21.97 kOe at 500 K can be obtained for MnBi ingots, respectively. Two-step thermal annealing can promote the transformation from the Mn and Bi phases to form LTP MnBi, allowing a maximum remanence of 38.3 emu/g to be acquired. Open recoil loops for MnBi ingots have never been reported and are worthy of investigation. It was found that the non-uniform distribution of the Mn phase, Bi phase, LTP MnBi, and even the amorphous phase, as well as their large variation in size, could produce a non-negligible local demagnetization field with non-uniform distribution and resulted in open recoil loops. Nearly closed recoil loops can be achieved by improving the non-uniform distribution of the microstructure. The dependence of the magnetic properties and the recoil loops on the microstructure was investigated in detail.

Improved Reliability and Mechanical Performance of Ag Microalloyed Sn58Bi Solder Alloys

Ag microalloyed Sn58Bi has been investigated in this study as a Pb-free solder candidate to be used in modern electronics industry in order to cope with the increasing demands for low temperature soldering. Microstructural and mechanical properties of the eutectic Sn58Bi and microalloyed Sn57.6Bi0.4Ag solder alloys were compared. With the addition of Ag microalloy, the tensile strength was improved, and this was attributed to a combination of microstructure refinement and an Ag3Sn precipitation hardening mechanism. However, ductility was slightly deteriorated due to the brittle nature of the Ag3Sn intermetallic compounds (IMCs). Additionally, a board level reliability study of Ag microalloyed Sn58Bi solder joints produced utilizing a surface-mount technology (SMT) process, were assessed under accelerated temperature cycling (ATC) conditions. Results revealed that microalloyed Sn57.6Bi0.4Ag had a higher characteristic lifetime with a narrower failure distribution. This enhanced reliability corresponds with improved bulk mechanical properties. It is postulated that Ag3Sn IMCs are located at the Sn–Bi phase boundaries and suppress the solder microstructure from coarsening during the temperature cycling, hereby extending the time to failure.

Preferred orientation of Bi and effect of Sn-Bi microstructure on mechanical and thermomechanical properties in eutectic Sn-Bi alloy

The grain sizes and grain orientations of Sn and Bi phases in Sn-58Bi alloy are investigated. We find that the grain size of Bi is larger than that of Sn. Tensile test and two-dimensional simulation reveal that the ductility and yield stress decrease upon Bi coarsening after 504 h of thermal aging at 80 ∘C, and that thermal stress is crowed on the Sn-Bi phase boundaries and is higher in Bi phase than that in Sn phase. Moreover, [0001] preferred orientation of Bi phase along the normal direction of the free surface of the casting model is observed.

Effect of Carbon Nanotube Addition on the Superconducting Properties of BSCCO Samples Textured via Laser Floating Zone Technique

In this research, the effect of carbon nanotube (CNT) addition on the structural and superconducting properties of Bi2Sr2CaCu2Oy + x wt% CNT materials with x = 0, 0.5, 1, and 3 prepared by solid state method, followed by directional grown using the laser floating zone (LFZ) technique has been investigated. XRD measurements showed that all samples are composed of almost single Bi-2212 phase. SEM images proved that Bi-2212 phase is the major one, with minor amounts of (Sr,Ca)3BiOx, and Bi-2201 secondary phases. According to the magnetic results, carbon nanotubes decrease Tc values and significantly reduce the magnetic hysteresis loops area and the magnetic critical current density.

Recovery of metastable dense Bi synthesized by shock compression

X-ray free electron laser (XFEL) sources have revolutionized our capability to study ultrafast material behavior. Using an XFEL, we revisit the structural dynamics of shock compressed bismuth, resolving the transition sequence on shock release in unprecedented details. Unlike previous studies that found the phase-transition sequence on shock release to largely adhere to the equilibrium phase diagram (i.e., Bi-V → Bi-III → Bi-II → Bi-I), our results clearly reveal previously unseen, non-equilibrium behavior at these conditions. On pressure release from the Bi-V phase at 5 GPa, the Bi-III phase is not formed but rather a new metastable form of Bi. This new phase transforms into the Bi-II phase which in turn transforms into a phase of Bi which is not observed on compression. We determine this phase to be isostructural with β-Sn and recover it to ambient pressure where it exists for 20 ns before transforming back to the Bi-I phase. The structural relationship between the tetragonal β-Sn phase and the Bi-II phase (from which it forms) is discussed. Our results show the effect that rapid compression rates can have on the phase selection in a transforming material and show great promise for recovering high-pressure polymorphs with novel material properties in the future.

Effect of BaFe12O19 Nanoparticles Addition on (Bi,Pb)-2223 Superconducting Phase

The aim of this work is to investigate the effect of BaFe12O19 nanoparticles on the microstructure, phase formation and mechanical properties of (Bi,Pb)-2223 superconducting phase. Co-precipitation and solid-state reaction techniques were used to synthesize BaFe12O19 nanoparticles and (BaFe12O19)x(Bi,Pb)-2223 superconducting samples with , respectively. BaFe12O19 nanoparticles and (BaFe12O19)x(Bi,Pb)-2223 structures were performed using X-ray diffraction. The morphology of BaFe12O19 nanoparticles and (BaFe12O19)x(Bi,Pb)-2223 were observed by means of transmission electron microscope (TEM) and scanning electron microscope (SEM), respectively. The experimental results reveal the composition of Bi-2223 phase and traces of Bi-2212 as a secondary phase when compared to the undadded sample. Lattice parameters are not altered with BaFe12O19 addition which indicate that nanoparticles do not enter the host crystal of (Bi,Pb)-2223. Vickers microhardness Hv is measured as function of indentation load and time. It was found that microhardness has a non-linear trend with applied load and time. The experimental results were analyzed using different models. The analysis revealed that the HK model was more suitable than the other approaches in estimating the load independent hardness of the samples.

Enhanced flux pinning properties in Bi1.6Pb0.4Sr2−xKxCa2Cu3O10+δ compounds

The effect of K substitutions on the structural and superconducting properties of Bi–Pb–Sr–Ca–Cu–O (BPSCCO) system has been investigated. Polycrystalline samples with stoichiometry of Bi1.6Pb0.4Sr2−xKxCa2Cu3O10+δ, where x = (0.00, 0.02, 0.04, 0.06, 0.08, and 0.1), were prepared by using the conventional solid state reaction technique. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) data showed that all samples consisted of high Tc (Bi-2223) and low Tc (Bi-2212) phases, and their volume fractions were found to vary with K content (x). The zero critical temperature was found to decrease from ~ (104.5 to 94.6) K, which was attributed to the decreases in hole carrier concentration. At 65 K, the magnetization critical current density (Jc) of the K-substituted samples was enhanced in comparison with that of the pure one. The Jc enhancement might be attributed to the formation of point defects resulting from the partial substitutions of K into Sr site in the BPSCCO system. In addition, the dominant pinning mechanism was found to be point-like pinning, as described using the Dew-Hughes model.