YBa2Cu3O7-δ Research Articles

Metal Propionate Solutions for High-Throughput Liquid-Assisted Manufacturing of Superconducting REBa2Cu3O7-δ (RE = Y, Gd, Sm, and Yb) Films.

The cost-effective synthesis of a series of metal propionate powders (copper, yttrium, barium, samarium, gadolinium, and ytterbium) is developed through single chemical reactions resulting in five novel crystalline forms. These complexes are valuable precursors for the preparation of epitaxial REBa2Cu3O7-δ (REBCO) superconducting films (here, RE = Y, Sm, Gd, and Yb) through the innovative transient liquid-assisted growth (TLAG) process based on chemical solution deposition (CSD). TLAG-CSD shows impressive results with YBa2Cu3O7-δ (YBCO), obtaining critical current densities of 2.6 MA/cm2 (77 K) on 500 nm films at unprecedented growth rates (50-2000 nm/s), boosting unprecedented high-throughput industrial production. With a cardinal concern on designing the pyrolysis toward optimal nanocrystalline films for TLAG, an analysis of the thermal behavior of the synthesized precursors is essential. Decomposition pathways for each metal propionate are established, and compatibility with TLAG-CSD is corroborated. Metal-organic solutions for these REBCO systems are successfully prepared, and their rheological properties and thermal behavior are analyzed. This work demonstrates homogeneous nanocrystalline films through propionate-based REBCO precursor solutions, including several rare-earth ions, which display exemplary chemical and microstructural characteristics crucial for TLAG, and provides a base for a wide variety of CSD-based functional oxides.

Study on rapid growth and improved performance of superconducting YBa2Cu3O7-δ coated conductors assisted by transient liquid phase

This study employs a fluorine-free metal organic deposition method (FF-MOD), with transient liquid phase assistance, to expedite the growth (TLAG) of superconducting YBa2Cu3O7-δ (YBCO) thin films on LaMnO3 metal substrates. The research evaluates the phase formation and performance of YBCO films with varying proportions of preformed BaZrO3 (BZO) nanocrystals. The experimental results indicate that the optimal proportion for incorporating BZO nanocrystals is 5 %, leading to the YBCO film displaying critical current density at 77 K under zero-field conditions. This achievement marks a significant advancement in the rapid growth of YBCO films on metal substrates with enhanced current-carrying capacity. Additionally, the research assesses the changes in overall uniformity and microstrain of YBCO films after the addition of BZO nanocrystals, shedding light on the key factors contributing to performance enhancement and offering insights for future improvements. This investigation offers valuable insights for attaining high-speed, high-performance growth of superconducting YBCO coating conductors.

Irradiation effects on copper oxide superconductors including high-entropy REBCO(HE-REBCO)

Polycrystalline specimens of copper oxide superconductors YBa2Cu3O7-δ(YBCO), Y0.39Sm0.30Eu0.31Ba2Cu3O7-δ(ME-REBCO), Y0.18La0.24Nd0.14Sm0.14Eu0.15Gd0.15Ba2Cu3O7-δ (HE-REBCO) were irradiated with 1 MeV-He ions at room temperature. Magnetization measurement using superconducting quantum interference device (SQUID) and microstructure observation using transmission electron microscope (TEM) were conducted before and after irradiation. The improvement of properties in HE-REBCO and degradations in YBCO, ME-REBCO were suggested by SQUID measurement. HE-REBCO had smaller irradiation defects and volume fractions although disappearance of twin boundaries due to tetragonal transition occurred in peak-damage area as well as YBCO. These defects work as optimal flux pinning centers leading to improve properties in HEREBCO.

Temporal Evolution of Defects and Related Electric Properties in He-Irradiated YBa2Cu3O7-δ Thin Films.

Thin films of the superconductor YBa2Cu3O7-δ (YBCO) were modified by low-energy light-ion irradiation employing collimated or focused He+ beams, and the long-term stability of irradiation-induced defects was investigated. For films irradiated with collimated beams, the resistance was measured in situ during and after irradiation and analyzed using a phenomenological model. The formation and stability of irradiation-induced defects are highly influenced by temperature. Thermal annealing experiments conducted in an Ar atmosphere at various temperatures demonstrated a decrease in resistivity and allowed us to determine diffusion coefficients and the activation energy ΔE=(0.31±0.03) eV for diffusive oxygen rearrangement within the YBCO unit cell basal plane. Additionally, thin YBCO films, nanostructured by focused He+-beam irradiation into vortex pinning arrays, displayed significant commensurability effects in magnetic fields. Despite the strong modulation of defect densities in these pinning arrays, oxygen diffusion during room-temperature annealing over almost six years did not compromise the signatures of vortex matching, which remained precisely at their magnetic fields predicted by the pattern geometry. Moreover, the critical current increased substantially within the entire magnetic field range after long-term storage in dry air. These findings underscore the potential of ion irradiation in tailoring the superconducting properties of thin YBCO films.

Fracture mechanisms and suppressed temperature effects of YBCO superconducting materials dominated by grain boundaries

YBa2Cu3O7-δ (YBCO) superconducting materials are typical polycrystalline materials, and the presence of intrinsic grain boundaries (GBs) is the main reason that affects superconductivity, in which high-angle GBs lead to low critical current density. There is no doubt that GBs also play an important role in the mechanical properties and fracture mechanisms of YBCO superconducting materials. In this work, the uniaxial tensile molecular simulations have been performed to investigate the fracture mechanisms of YBCO superconducting materials dominated by different types of GBs. The (100) single crystal and (110) twinning boundary models have been employed as comparative references. The results show that the low-angle GBs of YBCO consist of discontinuous dislocation cores, while the high-angle GBs are composed of a series of structural unit arrangements. Meanwhile, Young's modulus and ultimate tensile strength of YBCO can be enhanced by twin boundaries, while the other GBs have different effects on Young's modulus and ultimate tensile strength. In addition, the expansion of dislocation cores and the deformation of characteristic structural units are the main fracture mechanisms. More significantly, a novel temperature effect has been found to be significantly suppressed under the high-angle GBs. These findings not only provide a deep understanding of the GB structures, but may also provide guidance for modulating the mechanical properties of YBCO superconducting materials.

TMR-high-temperature superconductor composite magnetic sensor and its performance optimization

Tunnel magnetoresistance (TMR), recognized for its high sensitivity and low power consumption, holds significant promise in the domain of weak magnetic field detection. Using superconducting materials as magnetic concentrators can achieve several hundred to even a thousandfold amplification of magnetic fields, making it one of the most effective approaches to enhance the magnetic field resolution of TMR sensors. This paper utilized the flip-chip bonding process to integrate TMR with the high-temperature superconductor YBCO (YBa2Cu3O7-δ), and successfully developed TMR-YBCO composite magnetic sensor. Building upon this foundation, through optimization of the fabrication process and the pioneering use of a structural design incorporating the filling of annular holes with superconducting concentrators, the sensitivity of the sensor was further enhanced. Finally, the magnetic field resolution was increased by 1030 times compared to TMR sensors, reached to 2.9pT/Hz1/2 at 1 Hz. Simultaneously, results from frequency band testing indicated excellent frequency band characteristics, with a frequency response range exceeding kHz.

Tuning the superconducting performance of YBa2Cu3O7-δ films through field-induced oxygen doping.

The exploration of metal-insulator transitions to produce field-induced reversible resistive switching effects has been a longstanding pursuit in materials science. Although the resistive switching effect in strongly correlated oxides is often associated with the creation or annihilation of oxygen vacancies, the underlying mechanisms behind this phenomenon are complex and, in many cases, still not clear. This study focuses on the analysis of the superconducting performance of cuprate YBa2Cu3O7-δ (YBCO) devices switched to different resistive states through gate voltage pulses. The goal is to evaluate the effect of field-induced oxygen diffusion on the magnetic field and angular dependence of the critical current density and identify the role of induced defects in the switching performance. Transition electron microscopy measurements indicate that field-induced transition to high resistance states occurs through the generation of YBa2Cu4O7 (Y124) intergrowths with a large amount of oxygen vacancies, in agreement with the obtained critical current density dependences. These results have significant implications for better understanding the mechanisms of field-induced oxygen doping in cuprate superconductors and their role on the superconducting performance.

Edge cracking behavior of Y2O3 films based on the stress intensity factor

Hastelloy C-276 alloy is the preferred substrate for YBa2Cu3O7-δ (YBCO) coated conductors prepared by Ion-beam-assisted deposition (IBAD) route, but its surface is too rough to meet application requirements. Y(CH3COO)3·4H2O precursor solution has a low flattening efficiency, and its film edges are prone to crack formations. In this paper, a model for the stress intensity factor was established to study the effect of the presence of cracks on film stress. The simulation results showed that increasing the coating thickness reduced the overall stress, but increased the stress concentration at the crack. The larger bottom layer defects also made it easier for cracks to be generated. Then, 10-m long Hastelloy C-276/Y2O3 strips were prepared by colloidal-solution deposition planarization (CSDP), with an average surface roughness Rq of 0.427 and only 10 coating layers. This improved the flattening efficiency by 40 %, and a CeO2 layer with a good biaxial texture was finally prepared.

Effect of Doping on Phase Formation in YBCO Composites

This article discusses an effective method for obtaining superconducting composites based on Y1Ba2Cu3O7-δ (YBCO) by optimizing the total preparation time in comparison with similar scientific works while searching for effective modifying micro-additives. YBCO-based composites were doped with microparticles of aluminum, nickel, and iron. It was established that the initial ratio of green components, heat treatment, and holding time directly affect the qualitative and quantitative formation of the useful superconducting phase Y123, which in turn affects the basic superconducting properties of the final material.

Thoughts on the influence of Alex Mueller on high magnetic field technology

I briefly summarize some of the impacts that Alex Mueller's drive to discover superconductivity in low carrier density oxides has had on high magnetic field technology, especially on the desire to use the cuprate superconductors to generate magnetic fields now almost twice those possible with the Nb-based low temperature superconductors. There were some important lessons for applications of any new exotic temperature superconductor that had to be learned before the Bednorz and Mueller discovery could really impact applications. Above all is the lesson that a high transition temperature is no guarantee of applications unless conductors with high current density can be manufactured. Recent reports and hopes for an ambient pressure room temperature superconductor remind us that the hopes for pervasive superconducting technologies germinated with the discovery of superconductivity in LaBaCuO and went truly ballistic following the discovery of YBa2Cu3O7-δ (YBCO) with a 92 K transition temperature. Now that magnets made out of rare earth alloys of YBCO (REBCO) have entered routine service in NMR labs and prototype magnets made with REBCO appear ready to enable compact fusion reactors, we can finally say that Bednorz and Mueller's magnificent scientific achievement is having real world applications impact too.

Nanodiamond Influence on the Nucleation and Growth of YBCO Superconducting Film Deposited by Metal-Organic Decomposition.

It was recently shown that the introduction of nanodiamond (ND) into a superconducting metal-organic deposited YBa2Cu3O7-δ (YBCO) film produces an increase in critical current density in self-field conditions (B = 0 T). Such improvement appears to be due to the formation of denser and smoother films than the samples deposited without ND. This paper presents the work done to understand the role of ND during YBCO nucleation and growth. A detailed study on YBCO+ND films quenched at different temperatures of the crystallization process was carried out. Results showed that the reaction responsible for YBCO production appeared effectively affected by ND. In particular, ND stabilizes one of the YBCO precursors, BaF2(1-x)Ox, whose conversion into YBCO requires a prolonged time. Therefore, the YBCO nucleation is slowed down by ND and begins when the experimental conditions favor both thermodynamically and kinetically the formation of YBCO along the c-axis. This effect has important implications because the growth of a highly epitaxial c-axis YBCO film enables excellent superconducting performance.

Interrelations among zero-field critical current density, irreversibility field and pseudogap in hole doped high-Tc cuprates

Critical current density and the irreversibility magnetic fields are two parameters which control most of the applications of high-temperature superconductors. In this brief communications we have investigated the intrinsic effects that determine the magnitudes of these two parameters. The roles of hole concentration in the CuO2 plane (p) and oxygen deficiency (δ) in the CuO1-δ chains on the zero-field low-temperature critical current density, Jc0, were studied for a series of Y1-xCaxBa2Cu3O7-δ (x = 0.00, 0.05, 0.10, and 0.20) thin films. Jc0 above the optimum hole concentration were found to be high. The magnitude of Jc0 were largely determined by the hole concentration, maximizing at p ∼ 0.185 ± 0.005, regardless of the values of x and δ. This implied that oxygen deficiency/disorder plays a secondary role and the intrinsic Jc0 is governed largely by the number of doped holes in the CuO2 planes of Y1-xCaxBa2Cu3O7-δ. Further support in favor of this finding was garnered from the analysis of the in-plane resistive transitions of thin films of YBa2Cu3O7-δ (YBCO) with magnetic fields (H) applied along the crystallographic c-direction. The characteristic magnetic field (H0), linked to the vortex activation energy and the irreversibility field, exhibits similar p-dependence as shown by Jc0(p). We have explained these observations in terms of the doping dependent pseudogap (PG) energy/temperature scale in the low-energy electronic energy density of states observed in high-Tc cuprates. Both the intrinsic critical current density and the irreversibility field depend directly on the superconducting condensation energy, which in turn is primarily determined by the magnitude of the hole concentration dependent PG in the quasiparticle spectral density.

The Investigation of Vortex Motion in the YBCO Devices Manufactured Utilizing a Gaussian-shaped Optical Spot from a Continuous-wave Laser

The current report focuses on the analysis of the investigation results of the Abrikosov vortex motion in the YBa2Cu3O7-d (YBCO) device, which is a c-axis textured 0.3 ´ 50 ´ 100 µm3 (thickness ´ width ´ length) stripe of YBCO superconductor deposited on a LaAlO3 substrate. A laser beam focused in a Gaussian-shape optical spot of 5 mm in diameter modifies the stripe, initiating the oxygen out-diffusion and its uneven distribution in illuminated areas and in this way causing the appearance of a higher level of deoxygenation in the spot center and a lower level at its edges (slopes of weak superconductivity region). At temperatures below the temperature of the superconducting transition Tc, the current-self-produced magnetic field penetrates the optically modified area of the stripe in a form of Abrikosov magnetic vortices, and due to the current-self-produced Lorentz force, the vortices move toward their annihilation line resulting in energy dissipation. The vortices pinned on the slopes experience strong pinning and exert a magnetic drag force on moving vortices, which is confirmed by the stepped current-voltage dependences of the YBCO devices measured at temperatures 0.933·Tc £ T £ 0.958·Tc. Our results demonstrate the advantages of partially deoxygenated YBCO material for the development of superconducting electronic devices with electronic properties controlled by the motion of Abrikosov vortices at temperatures below Tc of the superconductor.

Investigation of magnetic and non-magnetic mechanisms for the attenuation of superconductivity in manganite/cuprate multilayers

We investigate the role strain-induced deoxygenation plays on the observed Tc attenuation in multilayers of La1/3Ca1/3MnO3 (LCMO) and YBa2Cu3O7-δ (YBCO), where a long-range ferromagnetic/superconductor proximity effect is proposed to exist. We compare changes to the superconducting Tc in several sets of oxygen-underdoped perovskite/YBCO/perovskite trilayers, where the perovskite layers consist of LCMO; LaNiO3 (LNO), which is structurally similar to LCMO but non-magnetic; and PrBa2Cu3O7-δ (PBCO), which is both non-magnetic and better lattice-matched with YBCO. We find that LCMO and LNO trilayers show similar Tc attenuation in response to decreasing annealing pressure. We also use x-ray absorption spectroscopy to directly gauge the hole concentration (p) in LCMO trilayers, where we find both thinner YBCO layers and greater oxygen underdoping decreases p. Our results indicate that strain-induced deoxygenation of the YBCO layer by itself can account for the observed Tc attenuation in LCMO/YBCO multilayers.

Natural strategies for creating non-equilibrium morphology with self-repairing capability towards rapid growth of excellent YBa2Cu3O7-δ crystals.

Self-repair, as a natural phenomenon, has been vastly observed and investigated in a variety of fields. With such an ability, living species self-heal their wounds to restore physiological functions while non-biological materials return to their original states, for example, thin surface layer growth occurs in the regeneration of incomplete KH2PO4 crystals. Here, two seeding strategies are developed for creating incomplete crystallographic shapes (i.e. right-angled concave corners) of YBa2Cu3O7-δ (YBCO) superconducting crystals with self-repairing capability in top-seeded melt growth. One involves in situ self-assembly seeding, by which the ability to self-repair promotes YBCO growth; the other is vertically connected seeding, by which self-repair triggers YBCO nucleation. Consequently, rapid surface crystallization originated at concave corners and swiftly generated initial growth morphology approaching equilibrium. Furthermore, these rapid-growth regions including the concave crystal or seed innately functioned as sizable effective seeding regions, enabling the enlargement of the c-oriented growth sector and the enhancement of properties for YBCO crystals. This work demonstrates experimentally that biaxial-in-plane-aligned crystals and precisely perpendicular-arranged seeds are important self-repairing activators for the rapid growth of YBCO crystals. This nature-inspired self-repairing work offers insights into the design of seeding architecture with non-equilibrium morphology for inducing sizable high-performance crystals in the YBCO family and other functional materials.

Growth of YBa2Cu3O7-δ superconducting films under different atmospheres by pulsed laser deposition

This paper aims to explore the epitaxial growth process for high-temperature superconducting YBa2Cu3O7-δ (YBCO) thin films by pulsed laser deposition (PLD) under different deposition atmospheres. The possibility of depositing YBCO superconducting thin films, under an oxygen-free environment, that was different from the oxygen atmosphere for most deposition processes of YBCO superconducting thin films was studied. Three different atmospheres, with oxygen, nitrous oxide, and nitrogen, were used in the experiment. The influence of atmospheric pressure on the formation and superconductivity of the YBCO phase were studied in detail. The characterization of structure and electrical properties of the thin films showed that YBCO thin films showed highly preferentially growth along the c-axis, had good superconductivity, and could be prepared under all three atmospheres. The formation of the YBCO phase at high temperatures did not need oxygen, and subsequent low-pressure oxygen-annealing process was only required at low temperatures of about 350 ℃. Our findings are of great significance for the preparation and application of YBCO thin films on substrates that were easy to oxidize at high temperatures, such as nickel strips or some electronic printed circuit boards.

Magneto-transport properties of YBCO:NaNbO3 (nanoparticles or nanorods) composite samples

In this study, the effect of addition of nanostructures of Sodium niobate (NaNbO3) having different morphology i.e. Nanoparticles (NPs) or Nanorods (NRs) on the magneto-transport properties of Y1Ba2Cu3O7-δ-NaNbO3 nanocomposite are investigated. NaNbO3 nanostructures are synthesized by hydrothermal technique whereas Pristine and NaNbO3 added Y1Ba2Cu3O7-δ (YBCO) samples are synthesized through Solid state reaction route. Superconducting transition in electrical measurement showed increased broadening with the increase in applied magnetic field. This broadening is smaller in YBCO composite samples than pristine YBCO indicating better coupling among superconducting grains in the nanocomposites. The tailing effect in the superconducting transition temperature is due to the flux flow of vortices. Further, the activation energy (Uₒ) estimated from ln(ρ) vs 1/T variation indicated its increased value in the nanocomposite YBCO showing enhanced flux pinning. From the applied magnetic field dependence of Uₒ for pristine YBCO and nanocomposite samples, the presence of planar and point defects was confirmed depending on the applied field value. The upper critical field (HC2(0)) estimated using Ginzburg-Landau (GL) theory indicated enhancement in HC2(0) for the nanocomposite samples, with larger enhancement in NPs added YBCO as compared NRs added YBCO. For 0.5 wt% NaNbO3 NPs added YBCO samples, the highest enhancement of HC2(0) (∼1.2 times) as compared to YBCO and other composite samples was achieved whereas further increase of concentration of NPs or NRs in YBCO compound leads to decrement in HC2(0) which is due to increased agglomeration between superconducting grains.

High-Tc Superconducting Josephson Junction Harmonic Mixers with Stub Tuners on Integrated Bowtie Antennas

Ordinary mixers can hardly meet the requirements in terahertz (THz) communications due to the low-power and expensive THz sources. Sensitive harmonic mixers have been widely studied to avoid this problem, owing to the fact that the higher the number of harmonics, the lower the local oscillator (LO) frequency, and the lower the cost. High-Tc superconducting (HTS) Josephson junction (JJ) mixers are performing candidates for THz receiver frontends because of the advantages of excellent sensitivity, wide bandwidth, high harmonic number and low LO power requirement. However, the normal-state resistance of HTS JJ is so low that traditional antennas are difficult to match it. In other words, it is quite a challenge to match the input impedance to a low input impedance for traditional antennas, especially for antennas fed by coplanar striplines (CPSs). In this work, based on the structure of bowtie, two types of stub tuners were integrated to decrease the impedance of the bowtie antenna so as to improve the coupling efficiency between the traditional bowtie antenna and the JJ. Furthermore, HTS YBa2Cu3O7-δ (YBCO) JJ harmonic mixers coupled with the proposed structures and fed by CPSs are fabricated and measured. The measurements show that the JJ mixer coupled with a pair of open-end stubs of the bowtie antenna achieves up to 88 harmonics, with a conversion efficiency of −69.6 dB. In contrast, the JJ mixer coupled with a pair of lumped-element stubs of the bowtie antenna only attains to 30 harmonics, with a conversion efficiency of −73.4 dB. Additional numerical simulations indicate that the coupling efficiency is enhanced when the complex impedance of the antenna is explicitly considered. Compared with other coupled traditional antennas, the JJ mixer with bowtie antenna has the largest harmonic number. This work paves the way for the future application of low-frequency and low-cost LO for THz communications.

Investigating the critical transitional temperature increase in graphene oxide doped bulk YBCO

Y1Ba2Cu3O7-δ (YBCO) was doped with thermally stable graphene oxide (TS-GO) and thermally unstable graphene oxide (TU-GO) in the following %wt. concentrations: 0.1, 0.5 and 0.7. TS-GO and TU-GO was characterized using RAMAN, fourier transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDX). The critical transition temperature (TCmid) increased in all TU-GO and TS-GO doped samples. The highest TCmid of 101 K was that of the 0.7 %wt. TU-GO doped sample. The increase in TCmid was greater for the samples doped with TU-GO. Non-stoichiometric oxygen content (δ) was seen to increase with an increase in doping concentration of both TS-GO and TU-GO. X-ray diffraction (XRD) analysis was carried out to determine the lattice parameters and phase characterization of the TU-GO and TS-GO doped samples. Lattice parameters show an increase in the copper oxide (CuO2) planar area with TCmid for TS-GO and TU-GO doping. To determine strain effects, the Williamson Hall method was used to determine the lattice strain (ɛ). The ɛ was seen to decrease for both TS-GO and TU-GO doped samples. The formation of magnetic manganese oxide nanoparticles in TS-GO and TU-GO doped samples was observed, and resulted from impurities found in the graphene oxide (GO) dopant material. The magnetic particles were extracted magnetically and characterized using EDX. YBCO was doped with trimanganese tetraoxide (Mn3O4) and manganese dioxide (MnO2) in a 0.1 and 0.2 %wt. concentration. The TCmid is seen to increase to 94 K and 104 K respectively for 0.1 %wt. MnO2 and Mn3O4 doped samples. The 0.2 %wt. doped Mn3O4 sample resulted in a decrease in TCmid. Magnetic susceptibility measurements confirmed a superconducting phase changes. The increase in TCmid above YBCO’s Tc = 93 K, correlates to the presence of manganese nano-impurities. This increase is hypothezied to be related to an increase in surface area of YBCO’s 2D copper oxide (CuO2) plane structure with GO doping.

The atomic layer thermopile heat flux sensor based on the inclined epitaxial YBa2Cu3O7-δ films

The atomic layer thermopile (ALTP) heat flux sensor based on highly c-axis oriented YBa2Cu3O7-δ (YBCO) films prepared on miscut 12° LaAlO3 substrates using magnetron sputtering is achieved. Benefiting from good biaxial texture, the YBCO film maintains a large Seebeck coefficient anisotropy, so the sensitivity of the ALTP heat flux sensor reaches 17.54 μV/(kW/m2). In addition, the response frequency of the sensor is higher than 1 MHz due to the high electrical conductivity of the prepared YBCO films, which is also higher than the current maximum (650 kHz) reported in the literature. These results indicate that our ALTP heat flux sensor can realize high-frequency heat flux detection above 1 MHz.