Properties Of YBa2Cu3O7 Research Articles

Carbon nanofibers addition on transport and superconducting properties of bulk YBa2Cu3O7\u2212\u03b4 material prepared via co-precipitation

The effects of carbon nanofibers addition on transport and superconducting properties of YBa2Cu3O7−δ (Y-123) superconductor were studied. Y-123 was prepared using co-precipitation method for good quality bulk of high temperature superconducting material. Carbon nanofibers with 0.2–0.8 wt% were added into Y-123 superconductors. The samples were characterized using electrical resistance measurement for critical temperature (Tc) and critical current density (Jc), powder X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray analysis. Most of the samples indicated a dominant Y-123 phase of an orthorhombic structure with a minor phase of BaCO3 and Y-124. Onset critical temperature was found to decrease from 90.5 to 80 K with increasing of carbon nanofibers concentration. The Jc for pure sample is 11 A/cm2 at 30 K while the Jc of sample with 0.4 wt% carbon nanofibers is 830 A/cm2 at 30 K. Introduction of carbon nanofibers enhanced Jc significantly. However, further addition of carbon nanofibers in Y-123 superconductor caused degradation in Jc.

Shear Elastic Properties of HTSC Ceramics in the Region of Superconducting Transition

The shear elastic properties of YBa2Cu3O7 –x high-temperature superconducting (HTSC) ceramics are studied near the superconducting transition at a temperature of 91.3 K and room temperature of 293 K. For the first time, a local increase in shear nonlinear acoustic parameter N in the region of the phase transition temperature was detected. Experimental studies of the linear and nonlinear elastic properties of YBa2Cu3O7 –x HTSC ceramics in the region of the superconducting transition showed that the electronic phase transition has a significant effect on its elastic properties. Based on experimental measurements, linear and nonlinear elastic parameters are determined both at room temperature and in the region of the phase transition.

Critical Current and Vortex Pinning Properties in YBa2Cu3O7- x Films With Ba2YTaO6 + Ba2YNbO6 and BaZrO3 Nanoinclusions by DC Transport and Microwave Measurements

The transport and vortex pinning properties of nanocomposite YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7-x</sub> (YBCO) film grown by pulsed laser deposition with addition of Ba <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Y(Nb/Ta)O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> (BYNTO) were compared with BaZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> added YBCO by DC (long-range vortex motion) and microwave (small-displacement vortex motion) measurement techniques. A high efficiency of BYNTO was observed in the field dependence and in the angular dependence of the critical current density J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> at 77 K, as well as in the field dependence of the complex surface impedance ΔZ. Based on the field dependence of the pinning parameters, such as the pinning parameter r and the pinning constant k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> , the vortex pinning regimes were discussed.

The effect of high-enthalpy argon plasma flow on the structure and properties of YBa2Cu3O7 – δ nanoceramics

The structure and electrical resistivity of YBa2Cu3O7 – δ-based nanostructured ceramics before and after exposure to the high-enthalpy argon plasma flow are investigated. It is demonstrated that the plasma-flow processing can strengthen the intergrain bonds in the surface layer of the ceramics and change its oxygen stoichiometry index.

Investigation and Comparing the Effects of CNTs and Ag Nanoparticles Doping on YBCO Superconductor Properties

In this work, we investigate and compare doping effects of Ag nanoparticles and carbon nanotubes (CNTs) on the properties of Y1Ba2Cu3 O 7−δ (YBCO) high-temperature superconductor. The YBCO samples were prepared using sol-gel method and characterized by resistivity versus temperature (ρ–T), the electrical field versus current density (E–J), x-ray diffraction (XRD) and scanning electron microscope (SEM) analysis. The results show that the orthorhombic phase of superconductivity was formed for all the prepared samples. Also, we found that the crystalline size of the YBCO samples decreases from 62 to 33 nm by adding CNTs and Ag nanoparticles to the compound. The pinning energy, critical current density and critical temperature of the samples increase by adding CNTs and Ag nanoparticles to YBCO compound, but CNTs play a more effective role than Ag nanoparticles in this compound.

Influence of Nano CeO2 on the Microstructures and Current Density of Preform Optimized Infiltration Growth-Processed Bulk YBa2Cu3 O 7−δ Superconductors

The effect of the addition of nanometric ceria (CeO2) on the physical properties of YBa2Cu3O7−δ superconductors is investigated. Preform optimized infiltration growth (POIG) process emerged as one of the advanced processing techniques to obtain the uniform distribution of fine Y2BaCuO5 (Y-211) particles of the order of ∼1 μ m. Nanoparticles of CeO2 were added to Y-211 in 0, 2, 5 and 10 wt% through a novel process called Nano Dispersive Sol Casting and subjected to POIG process. Nanometric CeO2 particles were distributed homogeneously throughout the Y-211 preform without any agglomeration. The micrographs of the final composites indicate refinement in Y-211 particle size and presence of defects in various length scales, starting from few nanometers to few microns. As the CeO2 content increased, the Y-211 particle size refined below 1 µm and, for 10 wt% of doping, even smaller than 0.5 µm. Elemental analysis confirmed the formation of different phases in the CeO2-added composites, due to which the superconducting transition is shown broadening. The sample with 10 wt% doping exhibited a stable Jc curve to high applied magnetic fields due to the presence of multiple peak fields. The present work demonstrates the introduction of fine microstructural defects for pinning the flux lines at different applied magnetic fields in POIG-processed YBCO composites.

Effect of water intercalation on the structure and electrophysical properties of YBa2Cu3O6.9

The influence of water vapors and plastic deformation on the structure and electrophysical properties of YBa2Cu3O6.9 (123) has been studied. It has been established that, at T = 200°C, the introduction of water into the structure of YBa2Cu3O6.9 leads to its transition into a defect tetragonal phase of the 124 type as a result of the formation of planar stacking faults. After annealing at T = 930°C, these defects are partially retained and are efficient centers of pinning in the magnetic fields applied perpendicularly to the c axis, which makes it possible to increase (by an order of magnitude) the critical current density in the high-textured ceramics at 77 K in the external magnetic field of 5–10 T. The plastic deformation of the hydrated ceramics favors the reverse transition of the arising 124 phase to the 123 phase at T = 930°C and is accompanied by a recrystallization of the material, which leads to the appearance of a texture and an increase the critical current density.

Comparison of Mechanical and Superconducting Properties of YBaCuO and GdBaCuO Single Grains Prepared by Top-Seeded Melt Growth

It is known that mechanical properties of a high-temperature superconductor (HTS) can affect the superconducting behaviour of the material. In this study, the mechanical and basic superconducting properties of single-domain YBaCuO and GdBaCuO were determined and compared. The bulk single-grain superconductor samples were prepared by top-seeded melt growth process. Distribution of trapped fields in the samples was mapped using the Hall probe technique. Levitation force was assessed using a dynamometer. Phase composition of the samples, was characterised by X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS) measurements. Microstructure was studied using scanning electron microscopy (SEM) and optical microscopy. Microhardness and comprehensive strength of the prepared samples were measured at a room temperature. The GdBaCuO superconductor has shown higher average hardness than the YBCO sample; higher fragility was also observed by comprehensive strength measurement of both types. Maximum trapped magnetic field was 0.65 T at 77 K in the case of a Gd-based material. In comparison with YBaCuO, the values of the trapped magnetic field and levitation force of GdBaCuO were higher. The results obtained can be useful for rare earth element (RE) superconductor device engineering as well as for the research in the field of superconducting ceramics.

Effects of electron-beam irradiation on the transition properties of YBa2Cu3O7−d grain boundary junctions

We have studied the effects of high-energy electron-beam irradiation on the transition properties of superconducting YBa2Cu3O7−d (YBCO) grain boundary junctions, bicrystal junctions and step-edge junctions, on SrTiO3 substrates. A uniform 1-MeV electron beam irradiated all over the samples. The irradiation doses were 0, 4.7 × 1014, 4.7 × 1015, and 4.7 × 1016 e/cm2. For each junction type, we used at least two samples for each dose level and compared the transition parameters before and after irradiation. For comparison, we also studied the same irradiation effects for YBCO microbridges. We measured the resistive transition temperature, the current-voltage characteristics, the normal-state resistance, and the critical current. The effect of irradiation was the most significant for the bicrystal grain-boundary junction and the least significant for the microbridges. The critical current data for the YBCO bicrystal grain-boundary junction showed a maximum at (0.47 ∼ 0.9) × 1015 e/cm2, and those for the microbridges showed a monotonic decrease with increasing dose. The normal-state resistance increased monotonically with increasing dose for all samples by up to ∼40% for the microbridges and ∼20% for the grain-boundary junctions at 4.7 × 1015 e/cm2. The change in the superconducting temperature (Tc) was negligible except for the bicrystal junction at 4.7 × 1016 e/cm2, which was not superconducting at 77 K. These results show that grain-boundary junctions are more susceptive to irradiation, indicating that their critical currents are controllable by using high-energy electron-beam irradiation.

Investigation of the properties of carbon-base nanostructures doped YBa2Cu3O7−δ high temperature superconductor

In this research, we have investigated the effects of three samples of carbon-base nanostructures (carbon nanoparticles, carbon nanotubes and silicon carbide nanoparticles) doping on the properties of Y1Ba2Cu3O7−δ (YBCO) high temperature superconductor. The pure and doped YBCO samples were synthesized by sol–gel method and characterized by resistivity versus temperature (ρ–T), current versus voltage (I–V), through X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis. The results confirmed that for all the samples, the orthorhombic phase of YBCO compound is formed. We found that the pinning energy and critical current density of samples increase by adding carbon nanostructures to YBCO compound. Also critical temperature is improved by adding carbon nanotubes to YBCO compound, while it does not change much for carbon and silicon carbide nanoparticles doped compounds. Furthermore, the samples were characterized by UV–vis spectroscopy in 300K and the band gap of the samples was determined. We found that the carbon nanotubes doping decreases YBCO band gap in normal state from 1.90eV to 1.68eV, while carbon and SiC nanoparticles doping increases it to 2.20 and 3.37eV respectively.

Micro-Structural Properties of YBa2Cu3O(7-x)/ZnO Nanorods on SrTiO3.

We examined the local structural and the interfacial properties of YBa2Cu3O(7-x) (YBCO)/ZnO nanorods on SrTiO3 (STO) substrates using various measurements. Vertically aligned ZnO nanorods were synthesized on STO substrates using a catalyst-free metal-organic chemical vapor deposition. YBCO films were deposited ex-situ on the ZnO nanorods/STO templates using a DC magnetron sputtering deposition. X-ray diffraction revealed that the YBCO films were crystallized along their c-axes on the ZnO nanorods/STO templates. Transmission electron microscopy measurements demonstrated that YBCO filled the space between ZnO nanorods and that both interfaces of YBCO/ZnO nanorods and ZnO nanorods/STO were quite clean with no disorder. Polarization-dependent extended X-ray absorption fine structure measurements at the Cu K edge showed extra disorder in the CuO2 planes of YBCO/ZnO nanorods/STO, compared with that of YBCO/STO. The superconductivity transition temperature (T(c)) of YBCO/ZnO nanorods/STO was approximately 50 K whereas that of YBCO/STO was 93 K. The decrease of T(c) of YBCO/ZnO nanorods/STO was ascribed to the structural disorder of CuO2 planes as well as grain boundaries in the YBCO films.

Magnetic properties of (CoFe2O4)x:(CeO2)1−x vertically aligned nanocomposites and their pinning properties in YBa2Cu3O7−δ thin films

Vertically aligned nanocomposites (VAN) combined ferrimagnetic CoFe2O4 with non-magnetic CeO2 ((CoFe2O4)x:(CeO2)1−x) in different phase ratios (x = 10%, 30% to 50%) have been grown by a pulsed laser deposition technique. Various unique magnetic domain structures form based on the VAN compositions and growth conditions. Anisotropic and tunable ferrimagnetic properties have been demonstrated. These ordered ferrimagnetic nanostructures have been incorporated into YBa2Cu3O7−δ thin films as both cap and buffer layers to enhance the flux pinning properties of the superconducting thin films. The results suggest that the ordered magnetic VAN provides effective pinning centers by both defect and magnetic nanoinclusions.

Effect of Artificial Defects on Electric and Magnetic Transport Properties in YBa2Cu3O7−δ Thick Film

The effect of 200 MeV Ag ions on YBa2Cu3O7−δ/5 wt.% Y2O3 composite thick films is studied. The structural deformity is analysed with X-ray diffraction showing reduced peak intensity. The decrease of transition temperature as a function of ion fluence has been observed from temperature-dependent resistivity and magnetization measurement. Fluctuation conductivity studied within the framework of Aslamazov–Larkin and Lawrence–Doniach theories fits well for 3D and 2D regimes with the appearance of critical region beyond 3D regime. Pseudogap temperature estimated above 100 K shifts to lower temperature zone as a function of ion doses. We report an enhancement of critical current density and flux pinning due to dual impact of swift heavy ion and Y2O3 inclusions at isothermal temperatures 40 K and 60 K.

Effect of Preform Compaction Pressure on the Final Microstructures and Superconducting Properties of YBa2Cu3O7−δ Superconductors Fabricated by Directionally Solidified Preform Optimized Infiltration Growth Process

Bulk YBa2Cu3O7−δ (YBCO, Y-123) superconductors with reasonable critical current densities J c are successfully fabricated in relatively short-time durations employing Directionally Solidified Preform Optimized Infiltration Growth Process (DS-POIGP). The effect of preform compaction pressure, applied to Y2BaCuO5 (Y-211) preform prior to the infiltration of liquid phases, on the end microstructures and current densities is investigated. It is found that a preform compaction pressure of 460 MPa resulted in samples with superior microstructures and superconducting properties. YBCO sample fabricated by DS-POIGP under optimized conditions revealed presence of fine-sized Y-211 particles distributed uniformly in the matrix of Y-123 causing large interfacial defect density (Y-211/Y-123). Extensive twinning on a nano-scale with twins in the size range of 40–100 nm is observed in the optimized sample. These microstructural parameters enabled a considerable improvement in the field dependence of J c . Irreversibility fields greater than 5.5 Tesla even at 77 K are achieved in the optimized sample fabricated by DS-POIGP.

Effect of deposition temperature on the orientation and electrical properties of YBa2Cu3O7−δ films prepared by laser CVD using liquid-source evaporation

Abstract YBa 2 Cu 3 O 7− δ (YBCO) films were prepared on a multilayer-coated Hastelloy C276 tape by laser chemical vapour deposition using liquid-source evaporation. The orientation of the YBCO films changed from a -axis to c -axis when the deposition temperature was increased from 1010 K to 1090 K. The c -axis-oriented YBCO film prepared at 1046 K exhibited critical temperature of 92 K and critical current density of 1.7 MA cm −2 at a deposition rate of 13 μm h −1 .

Fabrication and properties of YBa2Cu3O7−x ceramics at different sintering temperatures

The influence of sintering temperatures on the fabrication of YBCO ceramics under normal air atmosphere was investigated in this study. YBCO ceramics were prepared by mixing starting compounds of Y2O3, BaCO3 and CuO powders, which were calcined at 850°C for 12 h. The powder was pelletized and sintered at different temperatures, from 930°C–1050°C, for 12 h. Phase identification was carried out by x-ray diffraction (XRD) technique. Scanning electron microscopy (SEM) with energy dispersive x-ray analysis (EDS) was used to study microstructure and chemical composition. In addition, density, Vickers hardness properties, the change of resistance and dielectric properties with temperature above Tc were investigated. It was found that, at 950°C–1000°C, high-purity YBCO ceramic could be obtained. Outside this temperature range, either impurity phases were present or melting occurred. SEM images showed that grain size, which ranged from 1.5–2.5 µm, and hardness were related to density and liquid phase present in the sample. Furthermore, the sintering temperature affected oxygen content which, in turn, determined the conductive or semi-conductive behavior observed by electrical property measurement.

Josephson Junctions Made of YBa2Cu3O7-x Superconducting Nanofilms

Abstract Conventional Josephson junctions are used to build superconducting quantum interference devices (SQUIDs) which are the most sensitive magnetic field sensors known. Today, SQUIDS are widely used in many different areas like medical and biological research and diagnostics, geophysics, non-destructive evaluation of materials and structures, or fundamental physics research. In recent years the highly anisotropic and unique intrinsic properties of YBa2Cu3O7- x superconducting nano-films allowed fabrication of a special type of Josephson junctions, so-called π-junctions, which are excellent candidates as building block for fast, low-dissipative superconducting digital electronics or quantum computation. For those reasons fabricating high quality and reliably Josephson junctions has been one of the priority areas of research in superconductivity. There are several well-established technologies to fabricate Josephson junctions made of YBa2Cu3O7-x superconducting nano-films. Here I will briefly describe two of the most important ones used to fabricate both conventional Josephson junctions and π-junctions.

Influence of Deposition Pressure (O2) on the YBCO (Y123) Thin Films Prepared by Pulsed Laser Deposition

In this paper, the influence of oxygen pres- sure on film quality and superconducting properties of YBa2Cu3O7−δ(YBCO-Y123) thin films prepared by Pulsed Laser Deposition (PLD) was investigated. For this purpose, YBCO thin films were deposited on polished LaAlO3 (l00) (LAO) substrates at three different oxygen pressures (150, 200, and 250 mTorr). X-Ray Diffraction (XRD) and Scan- ning Electron Microscopy (SEM) techniques were used to make comparative studies of film microstructure. Except for oxygen pressures, all other variables such as number of pulses, repetition rate, deposition temperature, heating and cooling rate, target-substrate distance, laser excitation energy, annealing temperature, and annealing pressure were fixed. For this fixed set of parameters, SEM, XRD analy- sis, and AC susceptibility measurements of these films re- vealed that the crystal structure quality and superconducting

Effect of low-temperature treatment and subsequent high-temperature annealing on the critical current density of YBa2Cu3O y

The field dependences of the critical current density of the HTSC compound YBa2Cu3O y recovered at T = 920–950°C after the low-temperature treatment have been investigated. At T = 200°C, structural defects are formed in a wet environment, which are capable of initiating pinning of magnetic vortices. A short-term (1–3 h) recovery annealing performed at T = 930–950°C leaves in the samples a fairly large amount of structural defects formed during the low-temperature treatment, which results in a substantial increase in the critical current density in magnetic fields of ∼2 T as compared to the ceramics not subjected to double annealing. A longer high-temperature treatment removes the structural defects formed and brings the electrophysical properties of YBa2Cu3O y to the level characteristic of the ceramics produced by standard technology.

Flux-pinning properties of YBa2Cu3O7−x multilayered films with Y2O3 and ZnO nanoparticle inclusions

We investigated the flux-pinning properties of YBa2Cu3O7−x (YBCO) films in which Y2O3 and ZnO nanoparticles were uniformly embedded by using the pulsed laser deposition (PLD) technique. Y2O3 and ZnO nanoparticles with average sizes of 10–30 nm and with different densities by changing the number of nanoparticle layers were introduced in a YBCO matrix in the form of a multilayered structure. The total thickness of the YBCO superconducting layers was kept to be 250 nm. Dilute doping was found to be effective for both Y2O3 and ZnO nanoparticles. For Y2O3 doping, critical current density (Jc) enhancements over a wide range of fields were obtained in 1- and 5-layer doped samples, while weak Jc enhancements and a better field dependence of Jc were found in the YBCO film with 1 layer of ZnO. Based on an analysis of surface morphology, the transition temperature (Tc), and Jc, we discuss the difference between the two types of nanoparticles as flux-pinning centers.