Bi-Sr-Ca-Cu-O Research Articles

Experimental study of a high-temperature superconducting induction/synchronous motor with REBCO bulk bars for transportation applications

Lightweight and highly efficient high-temperature superconducting (HTS) rotating electric machines show great potential for transportation applications. An advantage of RE-Ba-Cu-O (REBCO, where RE=rare earth) bulk superconductors over stacked HTS tapes is their ability to carry larger and more homogenous currents. This study is the first in which an HTS induction/synchronous motor (HTS-ISM) with Gd-Ba-Cu-O (GdBCO) bulk superconductors has been successfully designed, fabricated, and tested. Our fabricated prototype featured a squirrel-cage rotor wound with 44 GdBCO bulk bars that were embedded in the rotor iron and connected at both ends using Y-Ba-Cu-O (YBCO) tapes to form a short circuit. First, the critical current of the bulk sample was investigated under a magnetic field perpendicular to its top surface at 77 K. Subsequently, no-load and load tests were performed in liquid nitrogen at different frequencies to verify the performance of the prototype. Finally, we thoroughly analyzed the differences between the proposed HTS-ISM that utilizes GdBCO bulk bars and developed HTS-ISMs that utilize a few turns of YBCO or Bi-Sr-Ca-Cu-O (BSCCO) tapes per bar.

Effect of suspension parameters towards the fabrication of BSCCO films by electrophoretic deposition

Superconductor Bi-Sr-Ca-Cu-O (BSCCO) thin films were fabricated on silver by electrophoretic deposition (EPD) method. By investigating the effects of solvents and I2 additives on the properties of suspension prepared of BSCCO powder, the particle charging mechanism is analyzed. Studying the effect of different solvents on the structure of BSCCO powder, isopropanol is the best dispersion solvent. Through the optimization of the I2 concentration, the results show that the optimal concentration of I2 is 0.08 mg ml−1. The processing parameters critically influencing the morphology of BSCCO films are identified and optimized to obtain uniform films with high packing density of BSCCO particles. After heated at 820 °C for 20 h, the smoothest surface morphology, high c-axis orientation, and highest critical temperature(Tc) of 82 K are obtained from the film prepared with optimized suspension.

Critical Current Density and Meissner Effect of Smart Meta-Superconductor MgB2 and Bi(Pb)SrCaCuO.

The smart meta-superconductor MgB2 and Bi(Pb)SrCaCuO increase the superconducting transition temperature (TC), but the changes in the transport critical current density (JC) and Meissner effect are still unknown. Here, we investigated the JC and Meissner effect of smart meta-superconductor MgB2 and Bi(Pb)SrCaCuO. The use of the standard four-probe method shows that Y2O3:Eu3+ and Y2O3:Eu3++Ag inhomogeneous phase significantly increase the JC, and JC decreases to a minimum value at a higher temperature. The Meissner effect was measured by direct current magnetization. The doping of Y2O3:Eu3+ and Y2O3:Eu3++Ag luminescent inhomogeneous phase causes a Meissner effect of MgB2 and Bi(Pb)SrCaCuO at a higher temperature, while the non-luminescent dopant reduces the temperature at which samples have Meissner effect. The introduction of luminescent inhomogeneous phase in conventional MgB2 and copper oxide high-temperature Bi(Pb)SrCaCuO superconductor increases the TC and JC, and Meissner effect is exerted at higher temperature. Therefore, smart meta-superconductivity is suitable for conventional and copper oxide high-temperature superconductors.

Reinforcing Increase of ΔTc in MgB2 Smart Meta-Superconductors by Adjusting the Concentration of Inhomogeneous Phases.

Incorporating with inhomogeneous phases with high electroluminescence (EL) intensity to prepare smart meta-superconductors (SMSCs) is an effective method for increasing the superconducting transition temperature (Tc) and has been confirmed in both MgB2 and Bi(Pb)SrCaCuO systems. However, the increase of ΔTc (ΔTc = Tc ‒ Tcpure) has been quite small because of the low optimal concentrations of inhomogeneous phases. In this work, three kinds of MgB2 raw materials, namely, aMgB2, bMgB2, and cMgB2, were prepared with particle sizes decreasing in order. Inhomogeneous phases, Y2O3:Eu3+ and Y2O3:Eu3+/Ag, were also prepared and doped into MgB2 to study the influence of doping concentration on the ΔTc of MgB2 with different particle sizes. Results show that reducing the MgB2 particle size increases the optimal doping concentration of inhomogeneous phases, thereby increasing ΔTc. The optimal doping concentrations for aMgB2, bMgB2, and cMgB2 are 0.5%, 0.8%, and 1.2%, respectively. The corresponding ΔTc values are 0.4, 0.9, and 1.2 K, respectively. This work open a new approach to reinforcing increase of ΔTc in MgB2 SMSCs.

Relationship between the TC of Smart Meta-Superconductor Bi(Pb)SrCaCuO and Inhomogeneous Phase Content.

A smart meta-superconductor Bi(Pb)SrCaCuO (B(P)SCCO) may increase the critical transition temperature (TC) of B(P)SCCO by electroluminescence (EL) energy injection of inhomogeneous phases. However, the increase amplitude ΔTC () of TC is relatively small. In this study, a smart meta-superconductor B(P)SCCO with different matrix sizes was designed. Three kinds of raw materials with different particle sizes were used, and different series of Y2O3:Sm3+, Y2O3, Y2O3:Eu3+, and Y2O3:Eu3++Ag-doped samples and pure B(P)SCCO were prepared. Results indicated that the TC of the Y2O3 or Y2O3:Sm3+ non-luminescent dopant doping sample is lower than that of pure B(P)SCCO. However, the TC of the Y2O3:Eu3++Ag or Y2O3:Eu3+ luminescent inhomogeneous phase doping sample is higher than that of pure B(P)SCCO. With the decrease of the raw material particle size from 30 to 5 μm, the particle size of the B(P)SCCO superconducting matrix in the prepared samples decreases, and the doping content of the Y2O3:Eu3++Ag or Y2O3:Eu3+ increases from 0.2% to 0.4%. Meanwhile, the increase of the inhomogeneous phase content enhances the ΔTC. When the particle size of raw material is 5 μm, the doping concentration of the luminescent inhomogeneous phase can be increased to 0.4%. At this time, the zero-resistance temperature and onset transition temperature of the Y2O3:Eu3++Ag doped sample are 4 and 6.3 K higher than those of pure B(P)SCCO, respectively.

On-Demand Local Modification of High-Tc Superconductivity in Few Unit-Cell Thick Bi2 Sr2 CaCu2 O8+δ.

High-temperature superconductors (HTSs) are important for potential applications and for understanding the origin of strong correlations. Bi2 Sr2 CaCu2 O8+δ (BSCCO), a van der Waals material, offers a platform to probe the physics down to a unit-cell. Guiding the flow of electrons by patterning 2DEGS and oxide heterostructures has brought new functionality and access to new science. Similarly, modifying superconductivity in HTS locally, on a small length scale, is of immense interest for superconducting electronics. A route to modify superconductivity locally by depositing metal on the surface is reported here by transport studies on few unit-cell thick BSCCO. Deposition of chromium (Cr) on the surface over a selected area of BSCCO results in insulating behavior of the underlying region. Cr locally depletes oxygen in CuO2 planes and disrupts the superconductivity in the layers below. This technique of modifying superconductivity is suitable for making sub-micrometer superconducting wires and more complex superconductingdevices.

Smart Metastructure Method for Increasing TC of Bi(Pb)SrCaCuO High-Temperature Superconductors

Improving the critical transition temperature (TC) of Bi(Pb)SrCaCuO (B(P)SCCO) high-temperature superconductors is important; however, considerable challenges exist. In this study, on the basis of the metamaterial structure and the idea that injecting energy will promote the formation of electron pairs, a smart meta-superconductor B(P)SCCO consisting of B(P)SCCO microparticles and Y2O3:Eu3++Ag or Y2O3:Eu3+ luminophore was designed. In the applied electric field, the Y2O3:Eu3++Ag or Y2O3:Eu3+ luminophore generates an electroluminescence (EL), thereby, promoting the TC via EL energy injection. A series of Y2O3:Eu3++Ag or Y2O3:Eu3+ luminous inhomogeneous phase-doped B(P)SCCO samples was prepared. Meanwhile, the B(P)SCCO sample doped with 0.2 wt% Y2O3 or Y2O3:Sm3+ nonluminous inhomogeneous phase was also prepared. Results indicated that the TC of 0.2 wt% Y2O3 or Y2O3:Sm3+ doping sample is lower than that of pure samples. However, the TC of the sample doped with 0.2 wt% Y2O3:Eu3++Ag or Y2O3:Eu3+ luminophore is higher than that of pure sample. This outcome further demonstrated that the smart metastructure method can improve the TC of B(P)SCCO.

Surface Morphology Studies on Laser Irradiated Target and Bi(Pb)SrCaCuO Thin Films

In this study, pulsed laser deposition technique was used to deposit bismuth plumbum strontium calcium copper oxide {Bi (Pb)SrCaCu0} thin films on MgO single crystal substrate. Solid state procedure which is inexpensive technique used in the production process of the Bi (Pb)SrCaCu0 superconductor bulk sample. In this work, Handy YAG Lasers (model: HYL 101 E) has been used. It is a high power class 4 solid state (ND: YAG) Q-switched pulsed laser and 532 nm (visible green: second harmonic) has been used to ablate the films. The substrate used in this work was single crystal MgO with the (100) orientation. Scanning Electron Microscopy (SEM) was used to observe the microstructure of fracture surface and cross section of thin film materials. Variable Pressure Scanning Electron Microscope (LEO-VPSEM) was used to study the correlation between the microstructure features. SEM studies have shown that the surface morphology of the bulk sample comprises platelets of average size ≈10μm with uniform and homogenous microstructure. The typical morphology of the as deposited films showed a continuous phase, granular structure, which spherical particles up to 5μm in diameter. The most prominent types of particulates BPSCCO films on MgO substrate are droplets with smooth surface, bigger droplets with granular surface, spherically-shaped features confined by randomly oriented facets, submicron rod-like features, Cu-enriched needles, platelets, irregularly-shaped Cu-rich outgrowths, strongly Cu-enriched tabular outgrowths, big target fragments, island growth structure, cubic and rectangular cubic structures. SEM analysis also showed that the deposition time have a pronounced influence on the particle size. The target morphology, which develops under laser-irradiation, depends on the laser fluence and the technique, by which the laser beam is moved relatively to the target during ablation. Laser-irradiated surfaces normally become altered both physically and chemically and morphological changes take the form of periodic structures such as ripples and ridges.

Ultrasound Assisted Mixing of Zinc Active Mass with Conductive Ceramic Additives for Ni-Zn Battery

Three zinc electrodes with carbon additive were prepared through ultrasound treatment. Two of them were mixed with conductive ceramic additives from the Bi-Sr-Ca-Cu-O (BSCCO) system with nominal chemical composition Bi1.7Pb0.3Sr2CuOx (B(Pb)SCCO 2201) and Bi1.7Pb0.3Sr2CaCu2Ox (B(Pb)SCCO 2212). The phase composition and morphology of the as-prepared samples were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The EDX specters suggest that the composition of the active mass does not change during the ultrasound treatment. The micrographs show that the active mass with carbon and 2201 additive has superior particle distribution compared to the other two samples.

Design of structural gigahertz multichanneled filter by using generalized Fibonacci superconducting photonic quasicrystals

Abstract The design-properties of one-dimensional photonic quasicrystals (PQC) are studied in a microwave frequency range using the transfer matrix method (TMM) and Gorter Casimir Two-Fluid Model (GCTM). The PQC is constructed by a dielectric (SiO2) and High Tc superconducting BSCCO (Bi2Sr2CaCu2O8) materials and organized following the Generalized Fibonacci class (GFC). We have shown that similar channels with zero transmission easily controlled by the order and the lattice parameters of quasiperiodic systems. The cutoff frequency of the opened central gap found at specific arrangement (m = n) is adjusted with changing the temperature and layer thickness of superconductor. The main heterostructure can be useful to design a gigahertz multi channeled filter with similar channels.

Growth of high-quality Bi2Sr2 CaCu2O8+\u03b4 whiskers and electrical properties of resulting exfoliated flakes

In this work, we demonstrate a simple technique to grow high-quality whiskers of Bi2 Sr2 CaCu2 O8+δ – a high Tc superconductor. Structural analysis shows the single-crystalline nature of the grown whiskers. To probe electrical properties, we exfoliate these whiskers into thin flakes (~50 nm thick) using the scotch-tape technique and develop a process to realize good electrical contacts. We observe a superconducting critical temperature, Tc, of 86 K. We map the evolution of the critical current as a function of temperature. With 2-D materials emerging as an exciting platform to study low-dimensional physics, our work paves the way for future studies on two-dimensional high-Tc superconductivity.

A Reproducible Approach of Preparing High-Quality Overdoped Bi2Sr2CaCu2O8+δ Single Crystals by Oxygen Annealing and Quenching Method**Supported by the National Natural Science Foundation of China under Grant Nos 11190022, 11334010 and 11534007, the National Basic Research Program of China under Grant No 2015CB921000, and the Strategic Priority Research Program (B) of Chinese Academy of Sciences under Grant No XDB07020300.

We report a reproducible approach in preparing high-quality overdoped Bi2Sr2 CaCu2 O8+δ (Bi2212) single crystals by annealing Bi2212 crystals in high oxygen pressure followed by a fast quenching. In this way, high-quality overdoped and heavily overdoped Bi2212 single crystals are obtained by controlling the annealing oxygen pressure. We find that, beyond a limit of oxygen pressure that can achieve most heavily overdoped Bi2212 with a Tc ∼63 K, the annealed Bi2212 begins to decompose. This accounts for the existence of the hole-doping limit and thus the Tc limit in the heavily overdoped region of Bi2212 by the oxygen annealing process. These results provide a reliable way in preparing high-quality overdoped and heavily overdoped Bi2212 crystals that are important for studies of the physical properties, electronic structure and superconductivity mechanism of the cuprate superconductors.

Interlayer tunneling spectroscopy of mixed-phase BSCCO superconducting whiskers

In this work, we present a study on the interlayer tunneling spectroscopy (ITS) of mixed-phase BiSrCaCuO (BSCCO) superconducting whiskers. The tunneling experiments were carried out on the artificial cross-whisker (twist angle of 90°) junctions. A multiple superconducting energy gap in the cross-whisker junctions was observed, which is attributed to the presence of different doping levels of two Bi2Sr2CaCu2O8+δ phases (Bi-2212), rather than two different phases, in the BSCCO whiskers, namely Bi2Sr2CaCu2O8+δ and Bi2Sr2Ca2Cu3O8+δ (Bi-2212 and Bi-2223). The temperature dependence of the energy gaps was discussed in the framework of the BCS T-dependence. On the other hand, the carrier concentration of the cross-whisker junction was changed by the carrier injection process. The effects of the carrier injection on the critical current, Ic, and the ITS of intrinsic Josephson junctions were investigated in details.

Vector-Potential Transformer With a Superconducting Secondary Coil and Superconducting Magnetic Shield

We created a complex coiled coil (vector-potential coil) to generate a curl-free vector potential. The device comprises a long flexible solenoid wound around a hollow nonmagnetic nonconducting cylinder; the entire coil has a coiled-coil structure. A straight superconducting BiSrCaCuO (BSCCO) wire was placed in the hollow cylinder at 77 K to serve as a secondary coil of a vector-potential transformer. We detected a nonmagnetic voltage induced between the ends of the secondary coil. The open-circuit voltage that was detected was the same as that of a normal conductor, i.e., a copper wire, which was also used as the secondary coil. Moreover, we replaced the hollow cylinder with a hollow superconducting BiPbSrCaCuO cylinder, which provides an ideal magnetic shielding. Even with the secondary coil inside the hollow BiPbSrCaCuO magnetic shield, the voltage induced across both BSCCO and copper secondary coils was identical to that measured when using the hollow nonmagnetic nonconducting cylinder.

Effects of the Sintering Conditions on the Structural Phase Evolution and T C of Bi1.6Pb0.4Sr2Ca2Cu3O7 Prepared Using the Citrate sol–gel Method

The effects of the sintering temperature and time on the phase evolution, microstructure and superconducting properties in a typical Pb-doped Bi-Sr-Ca-Cu-O (BSCCO) system, Bi1.6Pb0.4Sr2Ca2Cu3O7, were examined systematically by X-ray diffraction (XRD), thermo gravimetric-differential thermal analysis, scanning electron microscopy, and four-point probe resistivity measurements. The samples were prepared by the citrate based sol–gel method using their corresponding nitrates as the starting materials. The samples were sintered at different temperatures, ranging from 820 to 860 °C with different dwell-times (24–120 h). The results showed that the sintering temperature had a significant effect on the structure and superconducting transition temperature (TC). XRD showed that when the samples were heat treated at 550 °C, the BSCCO 2201 phase appeared, whereas peaks corresponding to the BSCCO 2112 phase were dominant at 800 °C. At 840 °C, only the peaks corresponding to the BSCCO 2212 and 2223 phases were detected with no impurities. A strong correlation was observed between the structural data andTC; the samples sintered at 840 °C for 120 h exhibited the maximum \(T_{\mathrm {C}}^{\text {onset}}\)(115.7 K).

A Three-Dimensional Fractal-Based Study of the Effects of the Complex Interface Between Bi <sub>2</sub>Sr <sub>2</sub>CaCu <sub>2</sub>O <sub>x</sub> Filaments and the Ag Matrix on the Mechanical Behavior of Composite Round Wires

Bi 2Sr 2CaCu 2O x/Ag/Ag-alloy (Bi2212) multifilamentary composite round wires (RWs) are the only RW candidate for fabricating superconducting magnets generating magnetic fields greater than 25 T. The complicated microstructure of the RWs, however, affects not only the electrical transport but also the mechanical behavior. To establish the correlation between the macroscopic electromechanical properties and the microstructure, an accurate characterization of the Bi2212 composite RW microstructure is important. Here, we develop a 3-D fractal-based model of the complex interface between Bi2212 filaments and the Ag matrix and determine its impact on RW mechanical behavior. The results indicate that such a complex interface strongly affects the local mechanical behavior rather than macroscopic behavior. Specifically, it causes the stress to be highly nonuniform in localized regions. At and/or around thin “Plate-like Extensions” (PEs) and “Bridge Connections” (BCs), the stress peaks under a simple uniaxial load. The results conclude that mechanical failure likely initiates at PEs, BCs, and the interface between them and the Ag matrix.

Electrothermal behavior and terahertz emission properties of a planar array of two Bi2Sr2CaCu2O8+δ intrinsic Josephson junction stacks

We report on the investigation of the electrothermal behavior and the terahertz (THz) emission properties of two nearby Bi2Sr2CaCu2O (BSCCO) intrinsic Josephson junction stacks, using a combination of electric transport and THz emission measurements plus low temperature scanning laser microscopy. We start with a compact BSCCO stack (placed in a z-shaped structure between two BSCCO electrodes) with lateral dimensions of and height, consisting of about 480 junctions. After characterization, a 200 nm wide slit was introduced by focused ion beam milling, splitting the stack into two halves connected by continuous superconducting electrodes. In a third step, the upper electrode was also split, leading to a structure where the two stacks can be biased separately. In all configurations hot-spot formation was observed. Despite the separation into two stacks only a single hot spot formed, which, depending on the bias condition, could either be located in one of the stacks or extend into both stacks with its center in the slit. In none of the structures it was possible to achieve mutual synchronization of the two stacks, indicating that additional synchronizing elements or the presence of a base crystal as for mesa structures may be necessary for the operation of parallel array structures.

Bi2Sr2CaCu2O8 intrinsic Josephson junction stacks with improved cooling: Coherent emission above 1 THz

We report on Bi2Sr2CaCu2O8 (BSCCO) intrinsic Josephson junction stacks with improved cooling, allowing for a remarkable increase in emission frequency compared to the previous designs. We started with a BSCCO stack embedded between two gold layers. When mounted in the standard way to a single substrate, the stack emits in the range of 0.43–0.82 THz. We then glued a second, thermally anchored substrate onto the sample surface. The maximum voltage of this better cooled and dimension-unchanged sample was increased and, accordingly, both the emission frequencies and the tunable frequency range were significantly increased up to 1.05 THz and to 0.71 THz, respectively. This double sided cooling may also be useful for other “hot” devices, e.g., quantum cascade lasers.

Evaluation of the Current-Limiting Properties for a Superconducting Current-Limiting Element With the Winding Direction of the Reactor of the Second Coil

The 2Generation (2G) high-temperature superconductivity (HTS) coated conductor has such advantages in the manufacture of current-limiting devices as fast phase transition, high critical current density, small degradation of critical characteristics under mechanical deformation, and lower cost of the manufacture of the superconducting current-limiting element due to its lower material cost compared to that of the Y-Ba-Cu-O (YBCO) thin film and the Bi-Sr-Ca-Cu-O (BSCCO) wire and bulk. However, in a resistive-type superconducting fault current limiter that was manufactured with a current-limiting device produced with a 2G HTS coated conductor, the dimensions of the current-limiting device will be larger than those of other devices (e.g., a YBCO thin film and a BSCCO bulk) due to the physical characteristics of the 2G HTS coated conductor. Moreover, application of such resistive-type superconducting fault current limiter to an actual power system will produce high cooling expenses. Therefore, in this study, the electric-coupling condition for the reduction of the size of the superconducting current-limiting element was presented, a superconducting current-limiting element was manufactured using a 2G HTS coated conductor with a stainless-steel stabilization layer, and the manufactured superconducting current-limiting element was applied to the electric-coupling condition to evaluate its stability and current-limiting performance under such condition. The electric-coupling condition that was presented in this paper is the series connection of the primary coil (N1) and the secondary coil (N2), and the parallel connection of the secondary coil and the superconductive element.

Doping dependence of low-energy quasiparticle excitations in superconducting Bi2212

The doping-dependent evolution of the d-wave superconducting state is studied from the perspective of the angle-resolved photoemission spectra of a high-Tc cuprate, Bi2Sr2CaCu2 O8+δ (Bi2212). The anisotropic evolution of the energy gap for Bogoliubov quasiparticles is parametrized by critical temperature and superfluid density. The renormalization of nodal quasiparticles is evaluated in terms of mass enhancement spectra. These quantities shed light on the strong coupling nature of electron pairing and the impact of forward elastic or inelastic scatterings. We suggest that the quasiparticle excitations in the superconducting cuprates are profoundly affected by doping-dependent screening.