Cu3 O7 Research Articles

Kinetic Control of Ultrafast Transient Liquid Assisted Growth of Solution-Derived YBa2 Cu3 O7 -x Superconducting Films.

Transient liquid assisted growth (TLAG) is an ultrafast non-equilibrium growth process mainly governed by kinetic parameters, which are only accessible through fast in situ characterizations. In situ synchrotron X-ray diffraction (XRD) analysis and in situ electrical resistivity measurements are used to derive kinetic diagrams of YBa2 Cu3 O7- x (YBCO) superconducting films prepared via TLAG and to reveal the unique peculiarities of the process. In particular, diagrams for the phase evolution and the YBCO growth rates have been built for the two TLAG routes. It is shown that TLAG transient liquids can be obtained upon the melting of two barium cuprate phases (and not just one), differentiated by their copper oxidation state. This knowledge serves as a guide to determine the processing conditions to reach high performance films at high growth rates. With proper control of these kinetic parameters, films with critical current densities of 2-2.6 MA cm-2 at 77 K and growth rates between 100-2000nm s-1 are reached. These growth rates are 1.5-3 orders of magnitude higher than those of conventional methods.

Analysing neutron radiation damage in YBa2 Cu3 O7- x high-temperature superconductor tapes.

Superconducting windings will be necessary in future fusion reactors to generate the strong magnetic fields needed to confine the plasma, and these superconducting materials will inevitably be exposed to neutron damage. It is known that this exposure results in the creation of isolated damage cascades, but the presence of these defects alone is not sufficient to explain the degradation of macroscopic superconducting propertiesand a quantitative method is needed to assess the subtle lattice damage in between the clusters. We have studied REBCO-coated conductors irradiated with neutrons to a cumulative dose of 3.3 × 1022 n/m2 that show a degradation of both Tc and Jc values, and use HRTEM analysis to show that this irradiation introduces ∼10 nm amorphous collision cascades. In addition, we introduce a new method for the analysis of these images to quantify the degree of lattice disorder in the apparently perfect matrix between these cascades.This method utilises Fast Fourier and Discrete Cosine Transformations of a statistically relevant number of HRTEM images of pristine, neutron-irradiated and amorphous samples and extracts the degree of randomness in terms of entropy values. Our results show that these entropy values in both mid-frequency band FFT and DCT domains correlate with the expected level of lattice damage, with the pristine samples having the lowest and the fully amorphous regions the highest entropy values. Our methodology allows us to quantify 'invisible' lattice damage to and correlate these values to the degradation of superconducting properties, and also has relevance for a wider range of applications in the field of electron microscopy where small changes in lattice perfection need to be measured.

Role of asymmetric critical current on magnetization loss characteristics of (RE)Ba2Cu3O7−d coated conductors at various temperatures

Commercial high-Tc superconducting (HTS) coated conductors exhibit asymmetric Ic(B,θ) characteristics, where B presents a DC magnetic field and θ is defined as the angle between an applied magnetic field and the normal component of the superconductor plane. The asymmetric Ic(B,θ) characteristics have a non-trivial influence on the dominant loss component, magnetization loss, of various HTS applications where HTS conductors are exposed to an AC magnetic field. Here, we present measurements of Ic(B,θ) and magnetization loss in a 12 mm-wide (Rare Earth)Ba2Cu3O7−d (REBCO) commercial coated conductor at 77, 70, and 65 K. In the Ic(B,θ) measurement, θ was varied around a full 360° revolution and B was varied up to 0.2 T. In terms of the magnetization loss measurement, the applied AC magnetic field amplitude is up to 110 mT and the field angle varied from 0° to 180°. At the three given temperatures, we observed magnetization loss variations among the field-angle range, in particular, for θ and 180°-θ, which are in mirror symmetry relative to the superconducting plane. Furthermore, this asymmetric field-angle dependence of the magnetization loss becomes more apparent at higher applied field amplitudes and lower operating temperatures. A finite element method simulation using H-formulation was carried out by directly interpolating the measured Ic(B,θ) data, and the simulation results reproduce the trend of the experimental results. We also found that the magnetization loss is not equivalent within the positive and negative half field cycles due to the asymmetric Ic(B,θ) characteristics of the conductor. Numerical simulations revealed a clear correlation between the magnetization loss and the asymmetric Ic(B,θ) data for the whole 360° field-angle range in the REBCO conductor. The asymmetry in the Ic(B,θ) data about the ab-peak causes differences in magnetization loss values for the mirror-symmetric field angles. The asymmetry in the Ic(B,θ) data upon field reversal also results in differences between magnetization loss values for the positive and negative cycles.

3D Uranyl Organic Frameworks Supported by Rigid Octadentate Carboxylate Ligand: Synthesis, Structure Diversity, and Luminescence Properties.

Seven three dimensional (3D) uranyl organic frameworks (UOFs), formulated as [NH4 ][(UO2 )3 (HTTDS)(H2 O)] (1), [(UO2 )4 (HTTDS)2 ](HIM)6 (2, IM=imidazole), [(UO2 )4 (TTDS)(H2 O)2 (Phen)2 ] (3, Phen=1,10-phenanthroline), [Zn(H2 O)4 ]0.5 [(UO2 )3 (HTTDS)(H2 O)4 ] (4), and {(UO2 )2 [Zn(H2 O)3 ]2 (TTDS)} (5), {Zn(UO2 )2 (H2 O)(Dib)0.5 (HDib)(HTTDS)} (6, Dib=1,4-di(1H-imidazol-1-yl)benzene) and [Na]{(UO2 )4 [Cu3 (u3 -OH)(H2 O)7 ](TTDS)2 } (7) have been hydrothermally prepared using a rigid octadentate carboxylate ligand, tetrakis(3,5-dicarboxyphenyl)silicon(H8 TTDS). These UOFs have different 3D self-assembled structures as a function of co-ligands, structure-directing agents and transition metals. The structure of 1 has an infinite ribbon formed by the UO7 pentagonal bipyramid bridged by carboxylate groups. With further introduction of auxiliary N-donor ligands, different structure of 2 and 3 are formed, in 2 the imidazole serves as space filler, while in 3 the Phen are bound to [UO2 ]2+ units as co-ligands. The second metal centers were introduced in the syntheses of 4-7, and in all cases, they are part of the final structures, either as a counterion (4) or as a component of framework (5-7). Interesting, in 7, a rare polyoxometalate [Cu3 (μ3 -OH)O7 (O2 CR)4 ] cluster was found in the structure. It acts as an inorganic building unit together with the dimer [(UO2 )2 (O2 CR)4 ] unit. Those uranyl carboxylates were sufficiently determined by single crystal X-ray diffraction, and their topological structures and luminescence properties were analyzed in detail.

Synthesis, structure and superconducting properties of laminated thin film composites of YBа2 Cu3 O7–d /Y2 O3 as components of 2G HTS wires

Synthesis, structure and superconducting properties of laminated thin film composites of YBа2 Cu3 O7–d /Y2 O3 as components of 2G HTS wires

Development of Low-Fluorine Solution for YBCO Film Growth

We developed a simple and stable precursor solution containing low fluorine content to fabricate YBa 2Cu 3O y (YBCO) films on CeO 2/YSZ/CeO 2 buffered NiW substrates. The fluorine content in the precursor solution could be controlled at 23.1% by tuning the ratio of barium trifluoroacetate to barium acetate. Fast pyrolysis process and smooth surface of YBCO precursor films could be acquired by using the low-fluorine solution. The phase, texture, microstructure, and superconducting properties of YBCO film were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscope, and four-probe method, respectively. The crystallized YBCO film showed good out-of-plane and in-plane textures. A high critical current density $J_{c}$ of ∼3 MA/cm 2 (77 K, 0 T) could be obtained in the YBCO/CeO 2/YSZ/CeO 2/NiW sample derived from the low-fluorine solution. The results indicate that the controllable fluorine content solution could be useful for epitaxial growth of YBCO films on buffered NiW substrates.

Enhanced Quench Protection in REBa2Cu 3Oδ-7-Based Coils by Enhancing Three-Dimensional Quench Propagation via Thermally Conducting Electrical Insulation

This simulation explores the effects of insulation properties on quench propagation in ReBa 2Cu 3O δ-7-based coils. At present, superconducting magnets primarily use insulators that are electrically and thermally insulating, for example, Kapton. Here, the impact of varying the thermal conductivity of the electrical insulation on quench behavior is reported. In particular, the behavior of a Kapton-insulated coil is compared with one insulated with doped TiO 2, one insulated with “ideal Al 2O 3”, and one noninsulated coil. The effects on minimum quench energy and normal zone propagation behavior are investigated. In addition, a new concept, the current sharing volume (CSV), which accounts for two- or three-dimensional normal zone propagation, is introduced. The CSV is defined as the volume of coil for which the temperature is above the current sharing temperature. The simulation results show that the transverse thermal conductivity and insulation thickness strongly influence the normal zone propagation velocity, thus impacting the quench detection time and hotspot temperature. As expected, the coils insulated with the higher thermal conductivity alternatives exhibited faster normal zone growth and lower hotspot temperatures relative to CSV growth. The impact of improved thermal conductivity of turn-to-turn insulation becomes even greater when distributed sensing replaces voltage-based sensing.

Two Mixed Superconducting Phases in (Hg, Re)-1223 Ceramics

We investigate Hg 0.82Re 0.18Ba 2Ca 2Cu 3O 8.76 polycrystalline samples with an optimum oxygen content aimed to analyze both their granular composition and to measure their magnetic response. We find out that the sample corresponds to a solid solution of two intrinsic structural superconductor phases. The AC magnetic susceptibility of a powder sample with a particle size of 20 μm have a critical temperature at 133 K. To make mesoscopic-scale particles of 600 nm in size, a sample of the powder was crushed and sieved. Now, the AC magnetic sample susceptibility shows two critical temperatures at 133 and 98 K. They have been described adopting a particular parametrization of the complex scalar field associated with the order parameter in a new framework of the Ginzburg–Landau theory. Thus, we propose a microscopic model to describe the dynamical interaction between these two types of grains.

Field Induced Kinetic Energy Density in YBa2Cu3O x Single Crystals

We report on experimental measurements of the magnetically induced kinetic energy density (Ek) in single-crystal samples of YBa 2Cu 3O x (YBCO), with the oxygen contents x=6.72, 6.78, 6.85, and 6.90. Our study is restricted to the reversible region near the critical temperature (Tc), where the pinning force acting on the vortices is negligible. We use the expression Ek=−M⋅B (M is the magnetization and B is the magnetic induction) to calculate the kinetic energy density from magnetization measurements carried out in magnetic fields up to 5 T. We analyze the behavior of Ek as a function of the temperature for several isofield curves and construct Ek versus B curves as well. We find that Ek rises with the increase of the charge carriers density. Granularity effects and dimensionality of the order parameter can also be important factors contributing to the kinetic energy density.

Enhanced Flux Pinning and Critical Current Density of $ \hbox{BaZrO}_{3}$-Doped $\hbox{Y}_{0.75} \hbox{Gd}_{0.25} \hbox{Ba}_{2} \hbox{Cu}_{3} \hbox{O}_{7-{\rm x}}$ Superconducting Films Prepared Using Advanced Low-Fluorine Solution

Y0.75 Gd0.25 Ba2 Cu3 O7- x (YGBCO) films with BaZrO3 (BZO) inclusions as pinning centers were prepared on LaAlO3 (00 l) substrates by metal-organic deposition via introducing zirconium (IV) acetylacetonate into the advanced low-fluorine YGBCO precursor solution. The BZO defects in the YGBCO film were found to induce the formation of a-oriented YGBCO grains on the film surface. An annealing process at a high temperature of 805 °C can completely eliminate the a-axis grains. The introduction of BZO defects in c-oriented YGBCO film can improve the film critical current density (Jc) and flux pinning of the films. Through the introduction of BZO nanostructure, the Jc of the YGBCO film processed at 805 °C was improved from 3 to 9 MA/cm2 at 77 K and 0 T. The flux pinning force density Fp also reached a high value of 38 GN/m3 at 65 K and 0.5-1 T.

バッファ層に CeO<sub>2</sub>/Y<sub>2</sub>O<sub>3</sub>/CeO<sub>2 </sub>を用いた Ni めっき Cu/SUS316 貼合せテープ上への YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7 </sub>超電導厚膜の作製

In this study, we attempted to install CeO 2 /Y2 O3 /CeO2 buffer layers, where the thicknesses of the CeO2 and Y 2O3 are10 and 250 nm respectively, instead of the CeO 2/YSZ (Y 2O3 stabilized ZrO 2)/CeO2 buffer layer architecture for YBCO (YBa 2 Cu3 O7 ) coated conductors using Ni-electroplated {100}<001> textured Cu and SUS316 laminated tape. Since the diffusion coefficient of oxygen in Y 2O3 is much smaller than that in YSZ and CeO 2, Y 2O3 seems to be a more favorable buffer layer material. We obtained a Jc of 1.0 MA/cm2 for the YBCO/Y 2 O3/Ni-electroplated Cu/SUS 316 laminated tape. However, the Δφvalue of the Y 2O3 layer deposited on the Ni layer increased by 1°compared with that of the Ni layer, and the Δφvalue of the YBCO layer on the Y 2O3 layer increased by 1.5°compared with that of the Y 2O3 layer. To avoid the degradation of the crystal orientations, we inserted very thin CeO2 layers of 10 nm between the Ni and the Y 2O3 layers, and between the Y 2O3 and the YBCO layers. The Jc of the 1 μm-thick YBCO layer prepared on the CeO 2 /Y2 O3 /CeO2 -buffered Ni-electroplated {100}<001> textured Cu/SUS316 laminated tape reached 2.1 MA/cm2 (Ic of 210 A-cm width) at 77 K in a self-field.

HRXRD analysis for YBa 2Cu 3O 7- x deposited on {001} LaAlO 3

YBa 2Cu 3O 7- x (YBCO) superconducting film was fabricated on {001} LaAlO 3 (LAO) substrate by pulse laser deposition (PLD), and its microstructure was examined by high resolution X-ray diffraction technology (HRXRD), such as pole figure, rocking curve, reciprocal space mapping. The results show that the YBCO crystalline alignment is almost {001} YBCO//{001} LAO, 〈100〉 YBCO//〈100〉 LAO besides 2% {001} YBCO//{001} LAO, 〈110〉 YBCO//〈100〉 LAO. The out-plane alignment of YBCO is some spreading (the breadth is 0.75°). There are 90°±0.65°〈110〉 twin domains in the film, which is caused by the high local stress and stress difference between 〈100〉 and 〈010〉 during the tetragonal to orthorhombic phase transition.

Fundamental and 3rd harmonic АС magnetic susceptibility of over-doped polycrystalline Y 1−xCa xBa 2Cu 3O 7−δ ( x = 0.025 and x = 0.20) samples

The inter-granular vortex dynamics of two polycrystalline samples Y 1− x Ca x Ba 2Cu 3O 7−δ ( x = 0.025 and 0.20) with different levels of over-doping is investigated by AC magnetic susceptibility measurements. The temperature dependence of the fundamental and 3-rd harmonic components of AC magnetic susceptibility shows that the sample with higher Ca content and level of over-doping is less influenced by the change of the AC magnetic field amplitude and frequency. The better inter-granular transport properties for sample Y 0.80Ca 0.20Ba 2Cu 3O 7−δ are related to the S–N–S type of the inter-granular links. The observed samples’ behavior is compared to the theoretical models of the AC magnetic response of a superconductor. The dynamical processes show a strong effect upon the inter-granular transition for both samples. Finally, a significant temperature misalignment between the imaginary components of the fundamental and 3-rd harmonic AC magnetic susceptibility is observed.

Formula omitted] and [formula omitted] characteristics in the Y 1− b(Ca) bBa 2Cu 3O 6+ x cuprate family

A model has been proposed to calculate the p ( x ) and T c ( x ) dependences in the Y 1− b (Ca) b Ba 2Cu 3O 6+ x high- T c cuprate family and applied to b = 0 , b = 0.1 , and b = 0.2 cases, for which experimental data exist in the literature. The results obtained imply that the Ca efficiency to provide holes is independent of the basal plane oxygen concentration, which is consistent with a view that electrons from CuO 2 layers would go primarily to Ca since it is twice closer than oxygen (in addition, the chain oxygen is screened by a layer made up of Ba and O(4) ions). It is shown that, in fully oxygenized compounds ( x = 1 ) the average efficiency, χ , of a chain oxygen to attract an electron from the two nearby layers is reduced by the Ca insertion, though not because the charge transfer mechanism is in itself weakened by Ca, but because a part of electrons that are otherwise available in CuO 2 layers has already been removed by the substitution of Y 3+ with Ca 2+. It has been found that the b -dependence of the average oxygen doping efficiency can be fairly accurately described by the following relation: χ ( b ) = 0.39 × ( 1 − 0.78 b ) . The calculated p ( x ) and T c ( x ) dependences are in very good agreement with the available experimental data.

The effect of BZO doping concentration and thickness dependent properties of YBCO films grown by PLD on buffered NiW substrates

The effect of BaZrO 3 (BZO) doping is systematically studied in YBa 2Cu 3O 6+ x (YBCO) thin films deposited by pulsed laser deposition (PLD) on buffered NiW substrates. Based on the structural and magnetic properties, the optimal BZO doping concentration is obtained to vary between 4 and 7.5 wt.%, depending mainly on applied magnetic field. This relatively high optimal concentration is linked to the nanograined target material and metal substrate that cause low-angle grain-boundaries and in-plane spread of YBCO crystals on NiW. Thickness dependent analysis of undoped and BZO-doped YBCO films predicts differences in growth mechanisms where early growth next to the substrate interface is 2D-type in BZO-doped films. This leads to the situation where crystallographic structure as well as superconducting properties are improved when the film develops and the thickness is increased. Therefore from the resistivity measurements a threshold thicknesses where reasonable properties occur are determined for both set of films. Measurements in thermally activated flux-flow regime (TAFF) indicate that above the threshold thickness relatively strong and isotropic vortex pinning is realized in BZO-doped YBCO films. Generally, this paper demonstrates that especially for thin film applications on NiW substrates even more compatible buffer layer structures should be utilized.

High performance fluorine-free MOD YBa 2Cu 3O 7-z film preparation by partial melting process

A partial melting process was developed to prepare the high performance YBa 2Cu 3O 7-z (YBCO) film with T c of 91 K on (0 0 l) LaAlO 3 (LAO) single crystal substrate through a non-fluorine polymer-assisted metal organic deposition (PA-MOD) approach. Influence of partial melting processing on the degree of biaxial texture, microstructure and superconducting properties of YBCO film was investigated. YBCO film prepared through the new process shows improved biaxial texture and surface morphology compared to those prepared with the conventional process. As a result, the superconducting properties of the film are significantly improved, and J c up to 3.5 MA/cm 2 (77 K, self field) has been achieved. The mechanisms underpinning the improved quality of the YBCO film by partial melting process are discussed.

Blocky and spheroidal growth in Y 1.5Ba 2Cu 3O x system

Solidification of Y 1.5Ba 2Cu 3O x system was studied with the aim to find the temperature of self-nucleation. The microstructure after cooling from isothermal dwells in the temperature range 984–995 °C was analysed. It is shown that blocky YBa 2Cu 3O 7−δ crystals were self-nucleated and grown during isothermal dwells below 988 °C and spheroidal multicrystals were formed during cooling from isothermal dwells at higher temperatures. The symmetrical and radial YBa 2Cu 3O 7−δ crystal branches of spheroids grow in the 〈110〉 crystal direction.

Temperature independent leakage current in Au/TbMnO 3/Y Ba 2Cu 3O 7− x capacitors

Au/TbMnO 3/Y Ba 2Cu 3O 7− x capacitors were fabricated on LaAlO 3 substrates and electrical characteristics were studied in the temperature range from 300 to 25 K. When temperature is higher than 225 K, Ohmic conduction is observed in the capacitors. Non-linear current–voltage characteristics are exhibited at low temperatures. Moreover, temperature-independent leakage currents are found at temperatures lower than 150 K. These electrical characteristics can be explained in terms of conduction transition originated from a thermal activation between 225 and 150 K, and the temperature-independent leakage currents are governed by the Poole–Frenkel emission and minor trap ionization energies.

Enhanced flux pinning in MOD-YBCO films with co-doping of BaZrO 3 and Y 2O 3 nanoparticles

A combined BaZrO 3 (BZO) and Y 2O 3 nanoparticles has been achieved in YBa 2Cu 3O 7− x (YBCO) films by metalorganic deposition using trifluoroacetates (TFA-MOD). The formation of integrated nanoparticles increases the critical current density ( J c) of Y 2O 3/BZO doped-YBCO films while keeping the critical transition temperature ( T c) close to that in the pure YBCO films. The YBCO film with 7.0 mol.% BZO and 7.0 mol.% Y 2O 3 showed T c value of 90 K and J c value of 6.5 mA/cm 2 at self-field (0 T, 77 K). The strongly enhanced flux pinning over a wide range of magnetic field can be attributed to the combined different crystal structures of BZO and Y 2O 3 created by optimized TFA-MOD conditions.

Magnetoresistivity and microstructure of YBa 2Cu 3O y prepared using planetary ball milling

We have studied the microstructure and the magnetoresistivity of polycrystalline YBa 2Cu 3O y (YBCO or Y-123 for brevity) embedded with nanoparticles of Y-deficient YBCO, generated by the planetary ball milling technique. Bulk samples were synthesized from a precursor YBCO powder, which was prepared from commercial high purity Y 2O 3, Ba 2CO 3 and CuO via a one-step annealing process in air at 950 °C. After planetary ball milling of the precursor, the powder was uniaxially pressed and subsequently annealed at 950 °C in air. Phase analysis by X-ray diffraction (XRD), granular structure examination by scanning electron microscopy (SEM), microstructure investigation by transmission electron microscopy (TEM) coupled with energy dispersive X-ray spectroscopy (EDXS) were carried out. TEM analyses show that nanoparticles of Y-deficient YBCO, generated by ball milling, are embedded in the superconducting matrix. Electrical resistance as a function of temperature, ρ( T), revealed that the zero resistance temperature, T co , is 84.5 and 90 K for the milled and unmilled samples respectively. The milled ceramics exhibit a large magnetoresistance in weak magnetic fields at liquid nitrogen temperature. This attractive effect is of high significance as it makes these materials promising candidates for practical application in magnetic field sensor devices.