YBCO Matrix Research Articles

Enhancing pinning ability by the addition of potassium niobate nanorods in YBCO superconductor

In the current study, we have investigated the effect of adding potassium niobate (KNbO3) nanorods (NRs) in YBCO superconductor to improve flux pinning properties. The KNbO3-NRs are synthesized by hydrothermal method, and KNbO3-YBCO nanocomposites are prepared by incorporating variable amounts of the NRs in YBCO matrix by solid-state reaction method. X-ray diffraction (XRD) pattern confirmed the orthorhombic phase of YBCO, KNbO3-NRs, and KNbO3-YBCO nanocomposite samples. The morphology and composition of the YBCO, KNbO3, and KNbO3-YBCO nanocomposites are studied using field emission scanning electron microscopy (FESEM) and energy-dispersive x-ray spectroscopy (EDX). Magnetic measurements of KNbO3-YBCO nanocomposites are carried out at temperatures from 15 to 65 K under an external magnetic field from -7 to + 7 T. The value of critical temperature (TC0) in xKNbO3-YBCO nanocomposites showed no significant decrease from the TC0 value obtained for YBCO, indicating that inserting a modest amount of KNbO3-NRs into the YBCO matrix does not result in substantial changes in TC0. The critical current density (JC) showed an enhancement of ∼ 3.6 times in 0.5wt%KNbO3-YBCO nanocomposite compared to YBCO. Additionally, when the concentration of KNbO3-NRs in YBCO was raised, the critical current density (JC) decreased due to the accumulation of KNbO3-NRs at the interfaces between grain boundaries. The rate of JC decay decreases as the externally applied field increases for nanocomposite samples compared to YBCO, showing an improvement in the pinning properties of nanocomposites.

Superconducting HfO2-added solution-derived YBa2Cu3O7 nanocomposite films: the effect of colloidal nanocrystal shape and crystallinity on pinning mechanism

Two different types of monoclinic HfO2 nanocrystals were employed in this work to study the effect of nanocrystal shape and crystallinity on the structural defects in the YBa2Cu3O7−δ (YBCO) matrix as it leads to an enhancement of pinning performances of solution-derived YBCO nanocomposite films. In this work the nanorod-like HfO2 nanocrystals obtained from surfactant-controlled synthesis led to short intergrowths surrounding the particles, while spherical HfO2 nanocrystals from the solvent-controlled synthesis led to the formation of long stacking faults in the YBCO matrix. It means that the small difference in crystallinity, lattice parameters, nanocrystal structures, core diameter of preformed nanocrystals in colloidal solutions have a strong influence on the formation of the structural defects around the particles in the YBCO matrix, leading to different pinning performances.

The influence of BaSnO3 and BaZrO3 nanoinclusions on the critical current and local structure of HTS coated conductors

We studied the effect of artificial pinning centers in the form of nanoinclusions of stannate BaSnO3 (BSO) and zirconate BaZrO3 (BZO) barium on the critical current of high-temperature superconducting tapes of the second generation (2G) based on YBa2Cu3O films (YBCO). It has been found that the introduction of BaZrO3 nanoinclusions increases the critical current at 77 K for the magnetic field direction parallel and normal to the tape surface, while the introduction of BaSnO3 nanoinclusions decreases the critical current in both cases. To elucidate the origin of a different impact of nanoinclusions we examined the local structure of the YBCO-matrix using x-ray absorption spectroscopy (EXAFS and XANES). The spectra were collected at K-edges of Cu, Sn, and Zr at the European Synchrotron (ESRF). It was revealed that the introduction of BaZrO3 nanoinclusions increases the stiffness of copper–oxygen bonds in superconducting CuO2 plane and minimizes their static disorder in the YBCO matrix, while the introduction of BaSnO3 nanoinclusions leads to a significant increase in static disorder with a relatively weak effect on the stiffness of Cu–O bonds. These changes in the local structure become decisive for changing the macroscopic properties of high-temperature superconductor-tapes.

Iron diffusivity into superconducting YBa2Cu3O7−δ at oxygen-assisted sintering: structural, magnetic, and transport properties

Optimization of materials exhibiting high-temperature superconductivity for producing controllable nano-devices is crucial for industrial applications. Herein we report a comprehensive study of the diffusion process between YBa2Cu3O7−δ (YBCO) and iron particles. Fe diffusion into the YBCO matrix could be fundamental for multilayer systems with YBCO/Fe-alloy interfaces. We have found that the orthorhombic YBCO structure adopts to 3 wt% Fe, while for higher Fe content, a formation of BaFeO3−δ and iron oxides was observed. Complementary measurements confirmed the strong superconductivity suppression in YBCO-Fe materials containing more than 7 wt% Fe. The YBCO with diffused Fe material retain the unit cell orthorhombicity (max. 3 wt% Fe), and their superconducting properties follow the principle of critical scaling with different exponents (γ). The critical current density (Jc), pinning fields (HP) exhibit γ = 1, the first critical field (Hc1) shows γ = 1/2, and critical temperature (Tc) demonstrates γ = 7/4.

Nanostructures and flux pinning properties in YBa2Cu3O7−y thin films with double perovskite Ba2LuNbO6 nanorods

Double perovskite Ba2LuNbO6 (BLNO)-doped YBa2Cu3O7−y (YBCO) thin films are fabricated on a SrTiO3 (001) substrate by pulsed laser deposition, and their nanostructures are characterized by transmission electron microscopy and scanning transmission electron microscopy. Cross-sectional observations and elemental mapping reveal that BLNO self-assembles during thin film deposition, and consequently, nanorods extending straight from the substrate to the surface are formed in the YBCO thin films. It is confirmed that stacking faults perpendicular to the growth direction disturb the formation of BLNO nanorods. Strain maps extracted by geometric phase analysis reveal that the tensile strain occurs in the YBCO matrix around the BLNO nanorods. Misfit dislocations are periodically introduced at the interface between the nanorod and the matrix, which results in the inhomogeneous strain of YBCO around the BLNO nanorods. The superconducting properties of the YBCO + BLNO thin films are compared with those of other previously reported YBCO thin films with normal perovskite and double perovskite nanorods.

Phase Formation and Conductivity Fluctuation Investigation in Nanoparticle SnO2-Added Y3Ba5Cu8O18 ± δ Polycrystalline Superconductor

The influence of 0, 0.20, 0.40, 0.50, and 0.60 wt % nano-sized tin oxide (SnO2) particles on electrical conductivity fluctuation in normal and superconducting state of the Y3Ba5Cu8O18 ± δ (denoted as Y‑358) polycrystalline samples is studied. Phase formation and microstructures have been systematically examined. By increasing the content of SnO2 in YBCO matrix, X-ray diffraction technique showed slight variation in lattice parameters and overall reduction in the orthorhombicity. Scanning electron microscopy observations and the crystallite size calculation also revealed that the grain size and the average crystallite size decreased compared to the SnO2-free sample. Aslamazov–Larkin and Lawrence–Doniach prototypes were used to analyze conductivity fluctuations based on the electrical resistivity ρ(T) measurements. Superconducting transition temperatures TC and TLD have been reported. The influence of SnO2 addition on the superconducting properties indicates that with the addition of SnO2 nanoparticles into Y-358 compound, some parameters values such as zero-resistance critical temperature TC zero, coherence distance alongside the c axis at 0 K ξc(0), and super-layer length d decrease in total, while anisotropy γ, critical magnetic fields Bc1(0), Bc2(0), and critical current density Jc(0) increase in SnO2-added Y-358 specimens compared to the pure one. The reasons corresponding to these scenarios are discussed in details.

Nanostructured templates for critical current density enhancement in YBa2Cu3O7–x films

YBa2Cu3O7–x (YBCO) films grown by metal-organic decomposition (MOD) are promising candidates for the production of high performance high temperature superconductors (HTS) tapes. Moreover, artificial pinning centers (APCs) introduction proved to be a powerful tool for the improvement of transport properties in YBCO films. Along with the widely employed pinning strategies, such as the introduction of secondary phases in the YBCO matrix, a less studied approach is the nanostructuring of the YBCO substrate, in order to hinder its growth and to obtain a highly defective superconductive layer. In this work, oxide nanostructures were deposited on crystalline substrates via polymer assisted deposition (PAD), a low cost, highly versatile technique, so as to create nanoparticles that could interfere with epitaxial growth of chemical YBCO films. Preliminary analyses of the superconducting films grown on BaZrO3 (BZO) and ZrO2 (ZO) nanostructures showed that the decorated templates are highly effective in straining the YBCO matrix, leading to a significant improvement in transport properties. In fact, we obtain an increase of the critical current density, at 77 K, for YBCO grown on BZO and ZO decorated substrate of the order of 3 times at 2 T and even of the order of 8 times at 5 T with respect to the YBCO grown on bare substrate. The improvement of the pinning properties can be related to the intrinsic modification of the crystal structure of YBCO film due to the presence of these nanoparticles, in agreement with transmission electron microscopy (TEM) analysis performed.

Lattice defect induced nanorod growth in YBCO films deposited on an advanced IBAD-MgO template

We have studied the growth of self-assembled BaHfO3 (BHO), BaZrO3 (BZO) and BaSnO3 (BSO) dopants in YBa2Cu3O6 + x (YBCO) films grown on CeO2 cap layered IBAD-MgO based metallic template by pulsed layer deposition process. The substrate induced defect formation and its impact on the growth of columnar-type of nanorods within the YBCO matrix is structurally investigated and their effect on critical current anisotropy is studied via molecular dynamics simulation model. We observed that the developed template greatly directs the growth mechanisms of different nanorods and thus modifies the critical current anisotropy of differently doped YBCO thin films.

Modifying the critical current anisotropy of YBCO films via buffering layers on IBAD-MgO based templates

The role of variations in the buffer layer structure of IBAD-MgO based templates on the critical current anisotropy has been investigated in undoped and BaZrO3 (BZO) doped YBa2Cu3O6+x (YBCO) films. Not only do the natural defects grow distinct within the undoped YBCO lattice but also due to the different lengths of BZO induced nanorods within the YBCO matrix, the flux pinning properties are greatly affected by the underlying layers which in turn has a great impact on the angular dependent critical current density J c(θ). This has been verified by transport measurements where the shape of the J c (θ) varies in accordance with the substrates. Based on our results, the template having a cap layer with the minimum lattice mismatch and a good chemical compatibility with deposited YBCO is proven to be the best for growing both the undoped and BZO doped YBCO films. Furthermore, a model we can present based on the shapes of J c(θ) curves depicts how the formation of nanosized defects affects the flux pinning anisotropy.

Self-assembled nanorods in YBCO matrix \u2013 a computational study of their effects on critical current anisotropy

In order to understand how the doping with self-assembled nanorods of different sizes and concentrations as well as applied magnetic fields affect the critical current anisotropy in YBa2Cu3O7−x (YBCO) thin films close to YBCO c-axis, we present an extensive and systematic computational study done by molecular dynamics simulation. The simulations are also used to understand experimentally measured Jc(θ) curves for BaHfO3, BaZrO3 and BaSnO3 doped YBCO thin films with the help of nanorod parameters obtained from transmission electron microscopy measurements. Our simulations reveal that the relation between applied and matching field plays a crucial role in the formation of Jc(θ)-peak around YBCO c-axis (c-peak) due to vortex-vortex interactions. We also find how different concentrations of different size nanorods effect the shape of the c-peak and explain how different features, such as double c-peak structures, arise. In addition to this, we have quantitatively explained that, even in an ideal superconductor, the overdoping of nanorods results in decrease of the critical current. Our results can be widely used to understand and predict the critical current anisotropy of YBCO thin films to improve and develop new pinscapes for various transport applications.

Enhanced superconducting performance in solution-derived YBCO–BaZrO3 composite film

YBa2Cu3O7-δ/BaZrO3 (YBCO/BZO) composite film with enhanced flux-pinning performance was prepared on LaAlO3 (LAO) substrate via a fluorine-free sol-gel method in combination with a novel photosensitive sol-gel lithography technique. Owing to the difference of lattice mismatch between the interfaces of YBCO/LAO and YBCO/BZO, high-density stacking faults were successfully introduced into YBCO matrix, which has been confirmed by XRD and HRTEM analysis. Magnetization measurement results indicate that YBCO/BZO composite film has a stronger current-carrying capacity than the pure YBCO film especially under applied magnetic fields. However, the critical current density of YBCO/CeO2 composite film is much lower than that of the pure YBCO film at all the applied magnetic fields due to the chemical reaction between YBCO and CeO2. Therefore, it can be concluded that the flux-pinning performance of YBCO film can be improved by the lattice distortions within YBCO matrix as long as the metal oxide microarrays cannot react with YBCO films.

Secondary phase particles in bulk, infiltration-growth processed YBCO investigated by transmission Kikuchi diffraction and TEM

We present results of the first application of the transmission Kikuchi diffraction (TKD) technique to bulk, infiltration growth (IG)-processed YBa2Cu3O7−δ (YBCO) superconductors with embedded Y2BaCuO5(Y-211) nanoparticles. By means of focused ion-beam (FIB) milling, TEM slices were prepared from mechanically polished surfaces of bulk, IG-processed YBCO samples. The required optical transparency was reached by additional polishing the resulting surfaces using the FIB and Ar-ion milling. For TKD, the sample was mounted on a homebuilt sample holder in the SEM, which provides the required inclination for TKD. The improved spatial resolution of TKD enabled the investigation of the small Y-211 particles (diameter of about 60–210 nm) embedded in the superconducting YBCO matrix. The fabricated TEM slices further enable the application of transmission electron microscopy to the same sample sections. These tiny Y-211 particles embedded within the YBCO matrix are, together with their strain fields, directly responsible for the high irreversibility fields due to the effective flux pinning of the IG-processed samples.

Дифференциальная термоЭДС углеродных нанотрубок типа "zigzag" во внешнем электрическом поле

The influence of (0.00, 0.20, 0.40, 0.50, and 0.60wt%) nano-sized tin oxide (SnO2) particles on electrical conductivity fluctuation in normal and superconducting state of the Y3Ba5Cu8O18±δ (denoted as Y-358) polycrystalline samples is studied. Phase formation and microstructures have been systematically examined. By increasing the content of SnO2 in YBCO matrix, X-ray diffraction technique showed slightly variation in lattice parameters and overall reduction in the orthorhombicity. Scanning electron microscopy observations and the crystallite size calculation also revealed that the grain size and the average crystallite size decreased compared to the SnO2 free sample. Aslamazov–Larkin and Lawrence–Doniach prototypes were performed to analyse conductivity fluctuations based on the electrical resistivity ρ(T) measurements. Superconducting transition temperatures Tc and TLD have been reported. The influence of SnO2 addition on the superconducting properties indicates that with the addition of SnO2 nanoparticles into Y-358 compound, some parameters values such as zero-resistance critical temperature Tc zero, coherence distance alongside the c axis at 0K ξc(0), and super-layer length d decrease in total, while anisotropy γ, critical magnetic fields Bc1(0), Bc2(0), and critical current density Jc(0) increase in SnO2-added Y-358 specimens compared to the pure one. The reasons corresponding to these scenarios are discussed in details.

Superconducting HfO2-YBa2Cu3O7−δ Nanocomposite Films Deposited Using Ink-Jet Printing of Colloidal Solutions

To reduce the fabrication costs while maximizing the superconducting and pinning properties of YBa2Cu3O7−δ (YBCO) nanocomposite films, the drop-on-demand ink-jet printing technique was used to deposit colloidal YBCO inks onto LaAlO3 substrates. These inks containing preformed HfO2 nanocrystals were carefully adjusted, prior to the jettability, as the droplet formation depends on the rheological properties of the inks themselves. After carefully adjusting printing parameters, 450-nm thick pristine YBCO films with a self-field critical current density (Jc) of 2.7 MA cm−² at 77 K and 500-nm thick HfO2-YBCO nanocomposite films with a self-field Jc of 3.1 MA·cm−² at 77 K were achieved. The final HfO2-YBCO nanocomposite films contained dispersed BaHfO3 particles in a YBCO matrix due to the Ba2+ reactivity with the HfO2 nanocrystals. These nanocomposite films presented a more gradual decrease of Jc with the increased magnetic field. These nanocomposite films also showed higher pinning force densities than the pristine films. This pinning enhancement was related to the favorable size and distribution of the BaHfO3 particles in the YBCO matrix.

Energy dependent structure of Xe ion tracks in YBCO and the effect on the superconductive properties in magnetic fields

The morphology and structure of damaged regions (tracks) produced by swift heavy 167, 77, and 46 MeV 132Xe23+ ions in YBCO-based second generation industrial high temperature superconductors wires (2G HTS) were studied using transmission electron microscopy. It was shown that ions produce tracks aligned along the ion trajectory but of morphology depending on their energy: continuous, nearly continuous, or discontinuous tracks like prolate ellipsoids of 10–15 nm in length and spheroids of 5 nm in diameter. The damaged regions of about 5 nm in diameter contain an amorphous material with a lower density compared to the pristine YBCO. The material density drops from 6300 kg m−3 for YBCO matrix to 3600 kg m−3 inside the tracks. Barium enrichment was found in the vicinity of the track at a distance of about 10 nm from the center of the defect. Ion damage tracks with different morphologies showed different effectivenesses as pinning centers. Tracks composed of discontinuous pinning centers—spheroids of about 5 nm in diameter—bring the best enhancement of the critical current density. It occurs for the lowest ion energy (46 MeV) in the range of energy loss of 8.9 keV/nm–4.7 keV/nm for Xe ions. The samples showed highest critical current densities of 56 MA/cm2 (4.2 K) and 3 MA/cm2 (77 K) in self-field, while in magnetic fields of 8 T, the values of 17 MA/cm2 (4.2 K) and 1.6 MA/cm2 (77 K) were achieved. The reduction of the superconducting volume corresponding to the amorphous radiation defects did not exceed 4% from the total sample volume.

Conductivity Fluctuation and Some Parameters of High temperature Superconductor Polycrystalline Y1Ba2Cu3O7−δ doped with Silver Nanoparticles

In this study, we report the effect of Ag nanoparticles doping on the dimensional fluctuations of superconducting order parameters, crystal structure, and some parameters of Y1Ba2Cu3O7−δ + × Ag (x = 0.0, 0.06, 0.1, 0.3, and 0.6 wt%) polycrystalline ceramics. By increasing the content of Ag in YBCO matrix, X-ray diffraction (XRD) with the Rietveld refinement technique revealed that the crystal lattice parameters changed and the orthorhombicity decreased slightly. Also, the increase of Ag wt% caused a decrease of superconducting transition temperatures (Tc) which are determined from the standard four-probe method and dropped abruptly. Aslamazov–Larkin (AL) model was used to analyze excess conductivity fluctuation. Lawerence–Doniach (LD) temperature named TLD which is responsible for the dimensional nature of fluctuation inside the grains is influenced by nano-silver combination in the compound. Crossover temperature from 2D to 3D (TLD) decreased in the mean-field region as a resultant dominance of 3D region by increasing of Ag in YBCO matrix. The decrease in zero-resistance critical temperature (Tc zero), zero-temperature coherence length along the c-axis ξc(0), and super layer length d values implies the degradation of inter-grain weak links, more disorder state of samples and unsettling of the mean free path for the charge carriers respectively with addition of silver nanoparticles. The calculations based on AL and LD model showed the highest anisotropy (γ = 1.34681) for the x = 0.6 sample. The size of the Ag ions, being larger compared to Cu ions, and the number of substitution sites affects the coupling between the CuO2 planes and that results in higher anisotropy. Critical magnetic fields Bc1(0), Bc2(0), and critical current density Jc(0) were indirectly calculated from the Ginzburg–Landau (GL) number and GL equations. By increasing the doping level of silver nanoparticle, these parameters were found to be higher in Ag-added YBCO samples compared to the pure Y123, meaning better intrinsic flux pinning properties of doped Y123. The silver nanoparticle inclusion reduces the grain size and increases the strength and hardness of the parent compound.

Control of nanostructure and pinning properties in solution deposited YBa2Cu3O7\u2212x nanocomposites with preformed perovskite nanoparticles

Solution deposited YBa2Cu3O7−x (YBCO) nanocomposites with preformed nanoparticles represent a promising cost-effective approach for superior critical current properties under applied magnetic fields. Nonetheless, the majority of YBCO nanocomposites with high nanoparticle loads (>20%) suffer from nanoparticle coalescence and degraded superconducting properties. Here, we study the influence of nanoparticle concentration (0–25% mol), size (5 nm–10 nm) and composition (BaHfO3, BaZrO3) on the generation of structural defects in the epitaxial YBCO matrix, key parameter for vortex pinning. We demonstrate that flash-heated superconducting nanocomposites with 20 mol% preformed BaHfO3 or BaZrO3 perovskite secondary phases feature discrete and small (7 nm) nanoparticles and high density of YBa2Cu4O8 (Y248) intergrowths. We identify a synergy between Y248 intergrowth density and small nanoparticles to increase artificial vortex pinning centers. Also, we validate the multideposition process to successfully increase film thickness of epitaxial nanocomposites with competitive critical currents Ic at 77 K.

BaZrO3 (BZO) nanoparticles as effective pinning centers for YBa2Cu3O7 − δ (YBCO) superconducting thin films

In-field pinning enhancement for high temperature YBCO superconducting thin film is one of the most significant issue towards future high field applications. Various pinning nanostructures have been designed to achieve better superconducting performance. In this work, BaZrO3 (BZO) has been introduced into YBCO for pinning enhancement. Small BZO nanoparticles with diameter of ~ 5 nm have been observed in the YBCO matrix with high film quality. The BZO-YBCO film deposited at 840 °C exhibits the highest transition temperature of 90 K. These small nanoparticles can provide effective pinning centers for the superconducting property enhancement of YBCO. By comparing the critical current density (Jc) performance of YBCO films, with or without incorporating BZO nanoparticles, 840 °C deposited BZO-YBCO exhibits obvious higher Jc values of 7.8 MA/cm2, 26.5 MA/cm2 and 64.5 MA/cm2 at the measured temperatures of 65 K, 40 K and 5 K, respectively. The results indicate an effective approach to achieve enhanced in-field performance of YBCO, by introducing small BZO nanoparticles.

Influence of Ba2+ consumption and intermediate dwelling during processing of YBa2Cu3O7 nanocomposite films

AbstractAchieving high‐critical current densities (Jc) with small artificial pinning centers is a crucial challenge for YBa2Cu3O7−δ (YBCO) nanocomposite thin films fabricated using chemical solution deposition methods. In this work, the YBCO texture, structure purity, and its Jc properties were improved by understanding the influence of preformed ZrO2 nanocrystals (Ba2+ consumption) during the nucleation and growth mechanism. This comprehensive study leads to an additional intermediate dwelling step during thermal process to increase the YBCO nuclei density before the YBCO growth, resulting to a self‐field Jc of 5‐6 MA/cm2 at 77 K for undoped and ZrO2‐doped YBCO films. Counter‐intuitively, the space and size distribution of the ZrO2 nanocrystals in the YBCO matrix are independent of this intermediate dwelling step.

Extended electronic structure inhomogeneity created by double chain layer defects surrounding columnar tracks in heavy-ion irradiated YBa2Cu3O7−δ

In YBa2Cu3O7−δ (YBCO), heavy-ion irradiation creates continuous amorphous tracks that are highly effective for vortex pinning. However, the electronic structure landscape of defects and consequently their vortex pinning roles are unclear. Here, we show double chain layer (DCL) defects which intersect the columnar tracks are additionally produced by high energy Pb ion irradiation in YBCO. The DCL defects are ∼29 nm long, about three times the columnar defect diameter. The electronic structures of the DCL and columnar track defects were determined using atomic-resolution scanning transmission electron microscopy (STEM) and high resolution electron energy loss spectroscopy (EELS). Results show a decrease in the oxygen and copper content at the interface between the track and the YBCO matrix, resulting in interfacial strain. For the DCL defects, the STEM/EELS study revealed a localized electron doped CuO2 plane next to the DCL defect. The DCL defects thus further extend the electronic inhomogeneity into YBCO.