Laser ablated YBa2Cu3O(7-x) high temperature superconductor coplanar waveguide resonator

NASA Technical Reports Server (NTRS)

Valco, G. J.; Blemker, A. R.; Bhasin, K. B.

1992-01-01

Several 8.8-GHz coplanar waveguide resonators are fabricated and tested that are made from laser ablated YBa2Cu3O(7-x) thin films on LaAlO3 substrates. A quality factor of 1250 at 77 K was measured. A correlation between the microwave performance of the resonators and the critical temperature and morphology of the films was observed.

Epitaxial growth of YBa2Cu3O7 - delta films on oxidized silicon with yttria- and zirconia-based buffer layers

NASA Astrophysics Data System (ADS)

Pechen, E. V.; Schoenberger, R.; Brunner, B.; Ritzinger, S.; Renk, K. F.; Sidorov, M. V.; Oktyabrsky, S. R.

1993-09-01

A study of epitaxial growth of YBa2Cu3O7-δ films on oxidized Si with yttria- and zirconia-based buffer layers is reported. Using substrates with either SiO2 free or naturally oxidized (100) surfaces of Si it was found that a thin SiO2 layer on top of the Si favors high-quality superconducting film formation. Compared to yttria-stabilized ZrO2 (YSZ) single layers, YSZY2O3 double and YSZ/Y2O3YSZ triple layers allows the deposition of thin YBa2Cu3O7-δ films with improved properties including reduced aging effects. In epitaxial YBa2Cu3O7-δ films grown on the double buffer layers a critical temperature Tc(R=0)=89.5 K and critical current densities of 3.5×106 A/cm2 at 77 K and 1×107 A/cm2 at 66 K were reached.

Processing of La(1.8)Sr(0.2)CuO4 and YBa2Cu3O7 superconducting thin films by dual-ion-beam sputtering

NASA Astrophysics Data System (ADS)

Madakson, P.; Cuomo, J. J.; Yee, D. S.; Roy, R. A.; Scilla, G.

1988-03-01

High-quality La(1.8)Sr(0.2)CuO4 and YBa2Cu3O7 superconducting thin films, with zero resistance at 88 K, have been made by dual-ion-beam sputtering of metal and oxide targets at elevated temperatures. The films are about 1.0 micron thick and are single phase after annealing. The substrates investigated are Nd-YAP, MgO, SrF2, Si, CaF2, ZrO2-(9 pct)Y2O3, BaF2, Al2O3, and SrTiO3. Characterization of the films was carried out using Rutherford backscattering spectroscopy, resistivity measurements, TEM, X-ray diffraction, and SIMS. Substrate/film interaction was observed in every case. This generally involves diffusion of the substrate into the film, which is accompanied by, for example, the replacement of Ba by Sr in the YBa2Cu2O7 structure, in the case of SrTiO3 substrate. The best substrates were those that did not significantly diffuse into the film and which did not react chemically with the film.

Low resistivity contacts to YBa2Cu3O(7-x) superconductors

NASA Technical Reports Server (NTRS)

Hsi, Chi-Shiung; Haertling, Gene H.

1991-01-01

Silver, gold, platinum, and palladium metals were investigated as electroding materials for the YBa2Cu3O(7-x) superconductors. Painting, embedding, and melting techniques were used to apply the electrodes. Contact resistivities were determined by: (1) type of electrode; (2) firing conditions; and (3) application method. Electrodes fired for long times exhibited lower contact resistivities than those fired for short times. Low-resistivity contacts were found for silver and gold electrodes. Silver, which made good ohmic contact to the YBa2Cu3O(7-x) superconductor with low contact resistivities was found to be the best electroding material among the materials evaluated in this investigation.

Formation of high-Tc YBa2Cu3O(7-delta) films on Y2BaCuO5 substrate

NASA Astrophysics Data System (ADS)

Wang, W. N.; Lu, H. B.; Lin, W. J.; Yao, P. C.; Hsu, H. E.

1988-07-01

High-Tc superconducting YBa2Cu3O(7-delta) films have been successfully prepared on green Y2BaCuO5 (2115) ceramic substrate. The films have been formed by RF sputtering and screen printing with post annealing at 925 C. Regarding superconducting features, the sharp resistivity drop with Tc onset around 95 K (midpoint 84 K) and 99 K (midpoint 89 K) has been observed for RF sputtered and printed films respectively. Both films show the excellent adhesion towards the 2115 substrate. Powder X-ray diffraction profiles indicate a majority of 1237 phase with preferred orientation for RF sputtered thin film.

Synthesis of YBa2CU3O7 using sub-atmospheric processing

DOEpatents

Wiesmann, Harold; Solovyov, Vyacheslav

2004-09-21

The present invention is a method of forming thick films of crystalline YBa.sub.2 Cu.sub.3 O.sub.7 that includes forming a precursor film comprising barium fluoride (BaF.sub.2), yttrium (Y) and copper (Cu). The precursor film is heat-treated at a temperature above 500.degree. C. in the presence of oxygen, nitrogen and water vapor at sub-atmospheric pressure to form a crystalline structure. The crystalline structure is then annealed at about 500.degree. C. in the presence of oxygen to form the crystalline YBa.sub.2 Cu.sub.3 O.sub.7 film. The YBa.sub.2 Cu.sub.3 O.sub.7 film formed by this method has a resistivity of from about 100 to about 600 .mu.Ohm-cm at room temperature and a critical current density measured at 77 K in a magnetic field of 1 Tesla of about 1.0.times.10.sup.5 Ampere per square centimeter (0.1 MA/cm.sup.2) or greater.

Large area ion beam sputtered YBa2Cu3O(7-delta) films for novel device structures

NASA Astrophysics Data System (ADS)

Gauzzi, A.; Lucia, M. L.; Kellett, B. J.; James, J. H.; Pavuna, D.

1992-03-01

A simple single-target ion-beam system is employed to manufacture large areas of uniformly superconducting YBa2Cu3O(7-delta) films which can be reproduced. The required '123' stoichiometry is transferred from the target to the substrate when ion-beam power, target/ion-beam angle, and target temperature are adequately controlled. Ion-beam sputtering is experimentally demonstrated to be an effective technique for producing homogeneous YBa2Cu3O(7-delta) films.

Laser ablated high T(sub c) superconducting thin YBa2Cu3O(7-x) films on substrates suitable for microwave applications

NASA Astrophysics Data System (ADS)

Warner, J. D.; Meola, J. E.; Jenkins, K. A.; Bhasin, K. B.

1990-04-01

The development of high temperature superconducting YBa2Cu3O(7-x) thin films on substrates suitable for microwave applications is of great interest for evaluating their applications for space radar, communication, and sensor systems. Thin films of YBa2Cu3O(7-x) were formed on SrTiO3, ZrO2, MgO, and LaAlO3 substrates by laser ablation. The wavelength used was 248 nm from a KrF excimer laser. During deposition the films were heated to 600 C in a flowing oxygen environment, and required no post annealing. The low substrate temperature during deposition with no post annealing gave films which were smooth, which had their c-axis aligned to the substrates, and which had grains ranging from 0.2 to 0.5 microns in size. The films being c-axis aligned gave excellent surface resistance at 35 GHz which was lower than that of copper at 77 K. At present, LaAlO3 substrates with a dielectric constant of 22, appears suitable as a substrate for microwave and electronic applications. The films were characterized by resistance-temperature measurements, scanning electron microscopy, and x ray diffraction. The highest critical transition temperatures (T sub c) are above 89 K for films on SrTiO3 and LaAlO3, above 88 K for ZrO2, and above 86 K for MgO. The critical current density (J sub c) of the films on SrTiO3 is above 2 x 10(exp 6) amperes/sq cm at 77 K. The T(sub c) and J(sub c) are reported as a function of laser power, composition of the substrate, and temperature of the substrate during deposition.

Magnetic flux relaxation in YBa2Cu3O(7-x) thin film: Thermal or athermal

NASA Technical Reports Server (NTRS)

Vitta, Satish; Stan, M. A.; Warner, Joseph D.; Alterovitz, Samuel A.

1992-01-01

The magnetic flux relaxation behavior of YBa2Cu3O(7-x) thin film on LaAlO3 for H parallel c was studied in the range of 4.2-40 k and 0.2-1.0 T. Both the normalized flux relaxation rate (S) and the net flux pinning energy (U) increase continuously from 1.3 x 10 exp -2 to 3.0 x 10 exp -2 and from 70-240 meV respectively, as the temperature (T) increases from 10 to 40 K. This behavior is consistent with the thermally activated flux motion model. At low temperatures, however, S is found to decrease much more slowly as compared with kT, in contradiction to the thermal activation model. This behavior is discussed in terms of the athermal quantum tunneling of flux lines. The magnetic field dependence of U, however, is not completely understood.

Improved epitaxial texture of thick YBa2Cu3O7-δ/GdBa2Cu3O7-δ films with periodic stress releasing

NASA Astrophysics Data System (ADS)

Lin, Jianxin; Yang, Wentao; Gu, Zhaohui; Shu, Gangqiang; Li, Minjuan; Sang, Lina; Guo, Yanqun; Liu, Zhiyong; Cai, Chuanbing

2015-04-01

Thick high-Tc superconducting films consisting of a YBa2Cu3O7-δ/GdBa2Cu3O7-δ periodic architecture are developed on oxid-buffered Hastelloy tapes using a pulsed laser deposition process. It is revealed that multilayer intermittent structures for superconducting layers are effective to avoid the presence of a-axis grains and microcracks that occur with increasing thickness, which are frequently observed in monolayer films of REBa2Cu3O7-δ (RE = Y, Gd, or other rare earths), such grains and cracks being the significant challenge for obtaining high critical current in coated conductors. Presently, the thicknesses of multilayer films vary from 0.5 μm to 3 μm and, based on the SEM images and x-ray φ-scans, hardly show the influences on the microstructures and grain orientation of the c-axis. Also, the characteristic Raman spectrum patterns and their shifting with increasing the thickness of YBCO/GdBCO imply that the superior texture is obtained due to the evolution of stress dominated by the compressive stress rather than tensile stress.

Investigation of Pb doping on electrical, structural and superconducting properties of YBa2-xPbxCu3O7-δ superconductors

NASA Astrophysics Data System (ADS)

Ezzatpour, S.; Sharifzadegan, L.; Sarvari, F.; Sedghi, H.

2018-06-01

In this study the high temperature superconductor YBa2-xPbxCu3O7-δ with doping x = ,0.05,0.1,0.15 were prepared by the standard solid-state reaction method. The effect of Pb substitution on Ba site of YBCO superconducting system, structural, electrical and superconducting properties of Y-based superconductor has been investigated. The measurements of dc resisitivity were performed on all samples with four-probe method using low frequency/lowAC current (4 mA) . The superconducting temperature, Tc, were determined from the resistivity versus temperature (R-T) curves. Results show that Pb doping reduced the cirtical temperature(Tc) and superconductivity properties of our samples. The maximum and the minimum Tc were observed for the samples with x = 0.15 and x = 0.1 respectively. The structure and phase purity of samples were examined by the X-ray powder diffraction technique (XRD) performed by means of D8 Advance Bruker diffractometer with Cu kα radiation. The grain morphology of surface of the samples was analyzed by sacanning electron microscopy (SEM). XRD patterns of polycrystalline materials of composition YBa2-xPbxCu3O7-δ revealed that all prepared samples are orthorhombic. All of the peaks of YBCO and YBa2-xPbxCu3O7-δ have been used for the estimation of volume fractions of the phases and ignored the void peaks.

Positron trapping in Y1-xPrxBa2Cu3O7-δ and the Fermi surface of YBa2Cu3O7-δ

NASA Astrophysics Data System (ADS)

Shukla, A.; Hoffmann, L.; Manuel, A. A.; Walker, E.; Barbiellini, B.; Peter, M.

1995-03-01

Temperature-dependent positron lifetime measurements in ceramic Y1-xPrxBa2Cu3O7-δ samples reveal positron trapping, in particular at low temperature and for small x. Positrons appear to be completely delocalized for T~400 K and higher. At high temperatures the lifetime for YBa2Cu3O7-δ and PrBa2Cu3O7-δ is identical (~165 ps) and close to the theoretical value. For these reasons a two-dimensional angular correlation of annihilation radiation (2D-ACAR) spectrum was measured in YBa2Cu3O7 at T=400 K. The spectrum width confirms the delocalization of the positron and the 2D-ACAR shows, apart from the one-dimensional Fermi surface due to CuO chains, a smaller Fermi surface sheet centered around the S point, in the first Brillouin zone.

High Tc screen-printed YBa2Cu3O(7-x) films - Effect of the substrate material

NASA Astrophysics Data System (ADS)

Bansal, Narottam P.; Simons, Rainee N.; Farrell, D. E.

1988-08-01

Thick films of YBa2Cu3O(7-x) have been deposited on highly polished alumina, magnesia spinel, nickel aluminum titanate (Ni-Al-Ti), and barium tetratitanate (Ba-Ti) substrates by the screen printing technique. Properties of the films were found to be highly sensitive to the choice of the substrate material. The film on Ba-Ti turned green after firing, due to a reaction with the substrate and were insulating. A film on Ni-Al-Ti had a Tc (onset) of about 95 K and lost 90 percent of its resistance by about 75 K. However, even at 4 K it was not fully superconducting, possibly due to a reaction between the film and the substrate and interdiffusion of the reaction products. The film on alumina had Tc (onset) of about 96 K, Tc (zero) of about 66 K, and Delta Tc of about 10 K. The best film was obtained on spinel and had Tc (onset) of about 94 K, zero resistance at 81 K, and a transition width of about 7 K.

High Tc screen-printed YBa2Cu3O(7-x) films - Effect of the substrate material

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.; Simons, Rainee N.; Farrell, D. E.

1988-01-01

Thick films of YBa2Cu3O(7-x) have been deposited on highly polished alumina, magnesia spinel, nickel aluminum titanate (Ni-Al-Ti), and barium tetratitanate (Ba-Ti) substrates by the screen printing technique. Properties of the films were found to be highly sensitive to the choice of the substrate material. The film on Ba-Ti turned green after firing, due to a reaction with the substrate and were insulating. A film on Ni-Al-Ti had a Tc (onset) of about 95 K and lost 90 percent of its resistance by about 75 K. However, even at 4 K it was not fully superconducting, possibly due to a reaction between the film and the substrate and interdiffusion of the reaction products. The film on alumina had Tc (onset) of about 96 K, Tc (zero) of about 66 K, and Delta Tc of about 10 K. The best film was obtained on spinel and had Tc (onset) of about 94 K, zero resistance at 81 K, and a transition width of about 7 K.

Structural morphology of YBa 2Cu 3O 7- x

NASA Astrophysics Data System (ADS)

Sun, B. N.; Hartman, P.; Woensdregt, C. F.; Schmid, H.

1990-03-01

The structural morphology of YBa 2Cu 3O 7- x (YBCO) has been investigated by application of the periodic bond chain (PBC) theory. For x=1, the F forms were found to be {001}, {011}, {013}, {112} and {114}. Attachment energies have been calculated in broken bond model and in an electrostatic point charge model. For x=1 the theoretical growth habit is tabular to platy {001} with {011} as side faces. For x=0 {010} also becomes an F form. The habit is isometric with large {001} and {011} and small {010} faces. The outermost layer of {001} contains half of the Cu + ( x=1) or Cu 3+ and O 2- ( x=0) ions in an ordered arrangement based on a c(2x2) quadratic lattice. For the outermost layer of (010) ( x=0) an ordering scheme of the copper and oxygen ions is proposed. The occurrence of {010} rather than {011} on grown crystals has to be ascribed to external factors.

Magnetoresistivity of thin YBa2Cu3O7-δ films on sapphire substrate

NASA Astrophysics Data System (ADS)

Probst, Petra; Il'in, Konstantin; Engel, Andreas; Semenov, Alexei; Hübers, Heinz-Wilhelm; Hänisch, Jens; Holzapfel, Bernhardt; Siegel, Michael

2012-09-01

Magnetoresistivity of YBa2Cu3O7-δ films with thicknesses between 7 and 100 nm deposited on CeO2 and PrBa2Cu3O7-δ buffer layers on sapphire substrate has been measured to analyze the temperature dependence of the second critical magnetic field Bc2. To define Bc2, the mean-field transition temperature Tc was evaluated by fitting the resistive transition in zero magnetic field with the fluctuation conductivity theory of Aslamazov and Larkin. At T → Tc the Bc2(T) dependence shows a crossover from downturn to upturn curvature with the increase in film thickness.

YBa2Cu3O7 thin films on nanocrystalline diamond films for HTSC bolometer

NASA Technical Reports Server (NTRS)

Cui, G.; Beetz, C. P., Jr.; Boerstler, R.; Steinbeck, J.

1993-01-01

Superconducting YBa2Cu3O(7-x) films on nanocrystalline diamond thin films have been fabricated. A composite buffer layer system consisting of diamond/Si3N4/YSZ/YBCO was explored for this purpose. The as-deposited YBCO films were superconducting with Tc of about 84 K and a relatively narrow transition width of about 8 K. SEM cross sections of the films showed very sharp interfaces between diamond/Si3N4 and between Si3N4/YSZ. The deposited YBCO film had a surface roughness of about 1000 A, which is suitable for high-temperature superconductive (HTSC) bolometer fabrication. It was also found that preannealing of the nanocrystalline diamond thin films at high temperature was very important for obtaining high-quality YBCO films.

Temperature and depth dependence of positron annihilation parameters in YBa2Cu3O7-x and La1.85Sr0.15CuO4

NASA Astrophysics Data System (ADS)

Lynn, K. G.; Usmar, S. G.; Nielsen, B.; van der Kolk, G. J.; Kanazawa, I.; Sferlazzo, P.; Moodenbaugh, A. R.

1988-02-01

The temperature dependence of the positron annihilation parameters for YBa2Cu3O7-x x=0.7, 0.4 and 0.0 and La1.85Sr0.15CuO4 were measured. The depth dependence of the YBa2Cu3O7 was studied using a variable-energy positron beam showing a strong depth dependence in the Doppler line-shape extending up to an average depth of ˜5.0 μm. It was found that a transition in the Doppler line-shape parameter, ``S'', was associated with the superconducting transition temperature (Tc) in YBa2Cu3O7-x x=0.4 and 0.0 while no transition was observed in the nonsuperconducting YBa2Cu3O6.3. Positron lifetime parameters in YBa2Cu3O7 were found to be consistent with positrons localized at open volume regions (probably unoccupied crystallographic sites) in this material with a lifetime of 210 psec at 300 K. These results indicate that the electron density at these unoccupied sites increases, using a free electron model, approximately 9% between 100 and 12 K.

Chemical nature of the barrier in Pb/YBa2Cu3O(7-x) tunneling structures

NASA Technical Reports Server (NTRS)

Vasquez, R. P.; Foote, M. C.; Hunt, B. D.; Bajuk, L.

1991-01-01

Several reports of reproducible tunneling measurements on YBa2Cu3O(7-x) thin films or single crystals with a Pb counterelectrode have recently appeared. The nature of the tunnel barrier, formed by air exposure, in these structures has been unknown. In the present work, the chemical nature of the tunnel barrier is studied with X-ray photoelectron spectroscopy (XPS). Laser-ablated films grown on LaAlO3 which have been chemically etched and heated in air are found to form nonsuperconducting surface Ba species, evident in an increase of the high binding energy Ba 3d and O 1s signals. A deposited Pb film about 10 A thick is found to be oxidized, and Cu(+2) is partially reduced to Cu(+1). The tunneling barrier thus appears to consist of species resulting from a combination of the air exposure and a reaction between the superconductor and the deposited Pb counterelectrode.

Artificial in-plane ordering of textured YBa2Cu3O(7-x) films deposited on polycrystalline yttria-stabilized zirconia substrates

NASA Astrophysics Data System (ADS)

Harshavardhan, K. S.; Rajeswari, M.; Hwang, D. M.; Chen, C. Y.; Sands, T. D.; Venkatesan, T.; Tkaczyk, J. E.; Lay, K. W.; Safari, A.; Johnson, L.

1992-12-01

Anisotropic surface texturing of the polycrystalline yttria-stabilized zirconia substrates, prior to YBa2Cu3O(7-x) film deposition, is shown to promote in-plane (basal plane) ordering of the film growth in addition to the c-axis texturing. The Jc's of the films in the weak-link-dominated low-field regime are enhanced considerably, and this result is attributed to the reduction of weak links resulting from a reduction in the number of in-plane large-angle grain boundaries.

Composition dependence of superconductivity in YBa2(Cu(3-x)Al(x))O(y)

NASA Technical Reports Server (NTRS)

Bansal, N. P.

1993-01-01

Eleven different compositions in the system YBa2(Cu(3-x)Al(x))O(y) (x = 0 to 0.3) have been synthesized and characterized by electrical resistivity measurements, powder X-ray diffraction, and scanning electron microscopy. The superconducting transition temperature T sub c (onset) was almost unaffected by the presence of alumina due to its limited solubility in YBa2Cu3O(7-x). However, T sub c(R = 0) gradually decreased, and the resistive tails became longer with increasing Al2O3 concentration. This was probably due to formation of BaAl2O4 and other impurity phases from chemical decomposition of the superconducting phase by reaction with Al2O3.

YBa2Cu3O x superconducting nanorods

NASA Astrophysics Data System (ADS)

Rieken, William; Bhargava, Atit; Horie, Rie; Akimitsu, Jun; Daimon, Hiroshi

2018-02-01

Herein, we report the synthesis of YBa2Cu3O x superconducting nanorods performed by solution chemistry. Initially, a mixture of fine-grained coprecipitated powder was obtained and subsequently converted to YBa2Cu3O x nanorods by heating to 1223 K in oxygen for 12 h. The nanorods are superconducting without the need for any further sintering or oxygenation, thereby providing an avenue for direct application to substrates at room temperature or direct use as formed nanorods. A critical superconducting transition temperature T c of about 92 K was achieved at a critical magnetic field of 10 Oe.

Subtle porosity variation in the YBa2Cu3O(7-x) high-temperature superconductor revealed by ultrasonic imaging

NASA Technical Reports Server (NTRS)

Roth, D. J.; Generazio, E. R.; Stang, D. B.; Hepp, A. F.

1990-01-01

The characterization of global porosity variation within a nominally 93-percent-dense specimen of YBa2Cu3O(7-x) high-temperature superconductor is reported. With a computer-controlled scanning system, precision ultrasonic velocity measurements were obtained at 100 micron increments over an 8- by 8-mm area of the YBa2Cu3O(7-x) specimen. The measurements were used to form a color map of velocity variation across the scanned region of the specimen. Subtle velocity variation on the order of 1 percent was observed. The specimen was shown by experimental methods to be single-phase, untextured, and free of nonuniform residual microstresses. From this knowledge and an established velocity-density relationship, a likely conclusion is that the observed velocity variations are solely due to porosity variations of similar magnitude. Locating these subtle porosity variations is critical since they can result in an order of magnitude variation in J(sub c) for dense YBCO specimens. Thus, mapping the global porosity distribution within YBa2Cu3O(7-x) may reveal regions that have poorer superconducting properties. Ultrasonic velocity results are translated into useful microstructural information for the material scientist.

Superconducting YBa2Cu3O7- δ Thin Film Detectors for Picosecond THz Pulses

NASA Astrophysics Data System (ADS)

Probst, P.; Scheuring, A.; Hofherr, M.; Wünsch, S.; Il'in, K.; Semenov, A.; Hübers, H.-W.; Judin, V.; Müller, A.-S.; Hänisch, J.; Holzapfel, B.; Siegel, M.

2012-06-01

Ultra-fast THz detectors from superconducting YBa2Cu3O7- δ (YBCO) thin films were developed to monitor picosecond THz pulses. YBCO thin films were optimized by the introduction of CeO2 and PrBaCuO buffer layers. The transition temperature of 10 nm thick films reaches 79 K. A 15 nm thick YBCO microbridge (transition temperature—83 K, critical current density at 77 K—2.4 MA/cm2) embedded in a planar log-spiral antenna was used to detect pulsed THz radiation of the ANKA storage ring. First time resolved measurements of the multi-bunch filling pattern are presented.

RAPID COMMUNICATION: Large-area uniform ultrahigh-Jc YBa2Cu3O7-x film fabricated by the metalorganic deposition method using trifluoroacetates

NASA Astrophysics Data System (ADS)

Araki, Takeshi; Yamagiwa, Katsuya; Hirabayashi, Izumi; Suzuki, Katsumi; Tanaka, Shoji

2001-07-01

Ultrahigh-Jc YBa2Cu3O7-x (YBCO) films have been successfully fabricated by the metalorganic deposition method using a trifluoroacetate coating solution which is prepared by a newly developed purification technique, the solvent-into-gel (SIG) method. The prepared pure coating solution has less than 0.25% impurities and has a wide flexibility in process conditions to obtain high-Jc YBCO film. Using this feature, we have successfully formed 50 mm diameter YBCO films, which have a critical current density over 10 MA cm-2 (77 K, 0 T) on LaAlO3 single crystalline substrates.

Magnetic flux relaxation in YBa2Cu3)(7-x) thin film: Thermal or athermal

NASA Technical Reports Server (NTRS)

Vitta, Satish; Stan, M. A.; Warner, J. D.; Alterovitz, S. A.

1991-01-01

The magnetic flux relaxation behavior of YBa2Cu3O(7-x) thin film on LaAlO3 for H is parallel to c was studied in the range 4.2 - 40 K and 0.2 - 1.0 T. Both the normalized flux relaxation rate S and the net flux pinning energy U increase continuously from 1.3 x 10(exp -2) to 3.0 x 10(exp -2) and from 70 to 240 meV respectively, as the temperature T increases from 10 to 40 K. This behavior is consistent with the thermally activated flux motion model. At low temperatures, however, S is found to decrease much more slowly as compared with kT, in contradiction to the thermal activation model. This behavior is discussed in terms of the athermal quantum tunneling of flux lines. The magnetic field dependence of U, however, is not completely understood.

Studies of anisotropic in-plane aligned a-axis oriented YBa(2)Cu(3)O(7-x) thin films

NASA Astrophysics Data System (ADS)

Trajanovic, Zoran

1997-12-01

Due to their layered planar structure, cuprate oxide superconductors possess remarkable anisotropic properties which may be related to their high transition temperatures. In-plane aligned a-axis YBa2Cu3O7 (YBCO) films are good candidates for such anisotropic studies. Furthermore, the full advantage of favorable material characteristics can be then utilized in applications such as vertical SNS junctions with the leads along the b-direction of YBCO and other novel junction configurations. High quality, smooth, in-plane aligned films are obtained on (100) LaSrGaO4. Form x-ray data, the films show complete b- and c-axes separation for the measured a-axis orientation. The anisotropic resistivity ratio (ρ c/ρ b), measured along the two crystallographic axes of single films gives ρ c/ρ b of ≈20 near the transition, with T cs near 90 K. In such films the grain boundary effects can be decoupled from the intrinsic anisotropic properties of YBCO. From oxygen annealing studies it was estimated that the CuO chains supply about 60% of the carriers. From J c measurements it is determined that the orientation of magnetic field with respect to the crystallographic film axes is the primary factor governing the J c values. The angular dependence of J c on the applied magnetic field is compared against various theoretical models showing the best agreement with the modified Ginzburg-Landau's anisotropic mass model (at T ≈ T c) and Tinkham's thin film model (at T < T c). By utilizing the Co-dopant, the coupling between CuO2 planes and the resulting enhancement of the intrinsic anisotropy of YBCO can be studied. Deposition and cooling conditions are shown to be the primary factor that influence the quality of dopant incorporation and the resulting oxygen ordering within the YBCO lattice. Various complex structures and devices utilizing in-plane aligned, a-axis films are presented. Other materials exhibiting in-plane alignment and a-axis growth are described. Optional substrates

Near-edge study of gold-substituted YBa2Cu3O(7-delta)

NASA Technical Reports Server (NTRS)

Ruckman, Mark W.; Hepp, Aloysius F.

1991-01-01

The valence of Cu and Au in YBa2Au0.3Cu2.7O7-delta was investigated using X-ray absorption near edge structure (XANES). X-ray and neutron diffraction studies indicate that Au goes on the Cu(1) site and Cu K-edge XANES shows that this has little effect on the oxidation state of the remaining copper. The Au L3 edge develops a white line feature whose position lies between that of trivalent gold oxide and monovalent potassium gold cyanide, and whose height relative to the edge step is smaller than in the two reference compounds. The appearance of the Au L3 edge suggests that fewer Au 3d states are involved in forming the Au-O bond in YBa2Au0.3Cu2.7O7-delta than in trivalent gold oxide.

Near-edge study of gold-substituted YBa2Cu3O(7-delta)

NASA Technical Reports Server (NTRS)

Ruckman, Mark W.; Hepp, Aloysius F.

1991-01-01

The valence of Cu and Au in YBa2Au0.3Cu2.7O7-delta was investigated using x-ray absorption near edge structure (XANES). X-ray and neutron diffraction studies indicate that Au goes on the Cu(1) site and Cu K-edge XANES shows that this has little effect on the oxidation state of the remaining copper. The Au L3 edge develops a white line feature whose position lies between that of trivalent gold oxide and monovalent potassium gold cyanide, and whose height relative to the edge step is smaller than in the two reference compounds. The appearance of the Au L3 edge suggests that fewer Au 3d states are involved in forming the Au-O bond in YBa2Au0.3Cu2.7O7-delta than in trivalent gold oxide.

Direct observation of twin deformation in YBa2Cu3O7-x thin films by in situ nanoindentation in TEM

NASA Astrophysics Data System (ADS)

Lee, Joon Hwan; Zhang, Xinghang; Wang, Haiyan

2011-04-01

The deformation behaviors of YBa2Cu3O7-x (YBCO) thin films with twinning structures were studied via in situ nanoindentation experiments in a transmission electron microscope. The YBCO films were grown on SrTiO3 (001) substrates by pulsed laser deposition. Both ex situ (conventional) and in situ nanoindentation were conducted to reveal the deformation of the YBCO films from the directions perpendicular and parallel to the twin interfaces. The hardness measured perpendicular to the twin interfaces is ˜50% and 40% higher than that measured parallel to the twin interfaces ex situ and in situ, respectively. Detailed in situ movie analysis reveals that the twin structures play an important role in deformation and strengthening mechanisms in YBCO thin films.

Forming YBa2Cu3O7-x Superconductors On Copper Substrates

NASA Technical Reports Server (NTRS)

Mackenzie, J. Devin; Young, Stanley G.

1991-01-01

Experimental process forms layer of high-critical-temperature ceramic superconductor YBa2Cu3O7-x on surface of copper substrate. Offers possible solution to problem of finishing ceramic superconductors to required final sizes and shapes (difficult problem because these materials brittle and cannot be machined or bent). Further research necessary to evaluate superconducting qualities of surface layers and optimize process.

Dominant pinning mechanisms in YBa2Cu3O7-x films on single and polycrystalline yttria stabilized zirconia substrates

NASA Astrophysics Data System (ADS)

Harshavardhan, K. S.; Rajeswari, M.; Hwang, D. M.; Chen, C. Y.; Sands, T.; Venkatesan, T.; Tkaczyk, J. E.; Lay, K. W.; Safari, A.

1992-04-01

Critical-current densities have been measured in YBa2Cu3O7-x films deposited on (100) yttria stabilized zirconia (YSZ) and polycrystalline YSZ substrates as a function of temperature (4.5-88 K), magnetic field (0-1 T) and orientation relative to the applied field. The results indicate that in films on polycrystalline substrates, surface and interface pinning play a dominant role at high temperatures. In films on (100) YSZ, pinning is mainly due to intrinsic layer pinning as well as extrinsic pinning associated with the interaction of the fluxoids with point defects and low energy planar (2D) boundaries. The differences are attributed to the intrinsic rigidity of single fluxoids which is reduced in films on polycrystalline substrates thereby weakening the intrinsic layer pinning.

Crystal growth of YBa2Cu3O(7-x) and reaction of gold crucible with Ba-Cu-rich flux

NASA Technical Reports Server (NTRS)

Tao, Y. K.; Chen, H. C.; Martini, L.; Bechtold, J.; Huang, Z. J.; Hor, P. H.

1991-01-01

YBa2Cu3O(7-x) crystals are grown in a gold crucible by a self-flux method. The flux moves along the gold surface due to surface wetting and leaves Y123 crystals behind. The obtained crystals are clean and have a size up to two millimeters and a Tc is greater than 90 K. In an effort to recycle the used crucibles, it is found that the used gold is contaminated by copper. A CuO thin film is easily formed on the surface of the crucible that is made of the used gold. This film provides good surface wetting and a buffer layer, which reduces the reaction between gold and the Y-Ba-Cu-oxide melt.

Growth and patterning of laser ablated superconducting YBa2Cu3O7 films on LaAlO3 substrates

NASA Technical Reports Server (NTRS)

Warner, J. D.; Bhasin, K. B.; Varaljay, N. C.; Bohman, D. Y.; Chorey, C. M.

1989-01-01

A high quality superconducting film on a substrate with a low dielectric constant is desired for passive microwave circuit applications. In addition, it is essential that the patterning process does not effect the superconducting properties of the thin films to achieve the highest circuit operating temperatures. YBa2Cu3O7 superconducting films were grown on lanthanum aluminate substrates using laser ablation with resulting maximum transition temperature (T sub c) of 90 K. The films were grown on a LaAlO3 which was at 775 C and in 170 mtorr of oxygen and slowly cooled to room temperature in 1 atm of oxygen. These films were then processed using photolithography and a negative photoresist with an etch solution of bromine and ethanol. Results are presented on the effect of the processing on T(sub c) of the film and the microwave properties of the patterned films.

Controlling particle properties in {{YBa}}_{2}{{Cu}}_{3}{{\\rm{O}}}_{7-\\delta } nanocomposites by combining PLD with an inert gas condensation system

NASA Astrophysics Data System (ADS)

Sparing, M.; Reich, E.; Hänisch, J.; Gottschall, T.; Hühne, R.; Fähler, S.; Rellinghaus, B.; Schultz, L.; Holzapfel, B.

2017-10-01

The critical current density {J}{{c}} in {{YBa}}2{{Cu}}3{{{O}}}7-δ thin films, which limits their application in external magnetic fields, can be enhanced by the introduction of artificial pinning centers such as non-superconducting nanoparticles inducing additional defects and local strain in the superconducting matrix. To understand the correlation between superconductivity, defect structures and particles, a controlled integration of particles with adjustable properties is essential. A powerful technique for the growth of isolated nanoparticles in the range of 10 nm is dc-magnetron sputtering in an inert gas flow. The inert gas condensation (IGC) of particles allows for an independent control of both the particle diameter distribution and the areal density. We report on the integration of such gas-phase-condensed {{HfO}}2 nanoparticles into pulsed laser deposited (PLD) {{YBa}}2{{Cu}}3{{{O}}}7-δ thin film multilayers with a combined PLD-IGC system. The particles and the structure of the multilayers are analyzed by transmission electron microscopy on cross-sectional FIB lamellae. As a result of the IGC particle implementation, randomly as well as biaxially oriented {{BaHfO}}3 precipitates are formed in the {{YBa}}2{{Cu}}3{{{O}}}7-δ thin films. With as few as three interlayers of nanoparticles, the pinning force density is enhanced in the low-field region.

Preparation of YBa2Cu3O7 High Tc Superconducting Coatings by Plasma Spraying

NASA Astrophysics Data System (ADS)

Danroc, J.; Lacombe, J.

The following sections are included: * INTRODUCTION * THE COMPOUND YBa2Cu3O7-δ * Structure * Critical temperature * Critical current density * Phase equilibria in the YBaCuO system * PREPARATION OF YBa2Cu3O7 COATINGS * General organisation of the preparation process * The powder * Hot plasma spraying of YBa2Cu3O7 * The post-spraying thermal treatment * CHARACTERISTICS OF THE YBa2Cu3O7-δ COATINGS * Chemical composition * Crystalline structure * Morphology of the coatings * Electrical and magnetic characteristics * Conclusion * REFERENCES

A new method for measuring low resistivity contacts between silver and YBa2Cu3O(7-x) superconductor

NASA Technical Reports Server (NTRS)

Hsi, Chi-Shiung; Haertling, Gene H.; Sherrill, Max D.

1991-01-01

Several methods of measuring contact resistivity between silver electrodes and YBa2Cu3O(7-x) superconductors were investigated; including the two-point, the three point, and the lap-joint methods. The lap-joint method was found to yield the most consistent and reliable results and is proposed as a new technique for this measurement. Painting, embedding, and melting methods were used to apply the electrodes to the superconductor. Silver electrodes produced good ohmic contacts to YBa2Cu3O(7-x) superconductors with contact resistivities as low as 1.9 x 10 to the -9th ohm sq cm.

Momentum Dependence of Charge Excitations in YBa2Cu3O7-δ and Nd2-xCexCuO4

NASA Astrophysics Data System (ADS)

Ishii, Kenji

2006-03-01

Resonant inelastic x-ray scattering (RIXS) studies at Cu K-edge on high-Tc superconducting cuprates, YBa2Cu3O7-δ and Nd2-xCexCuO4 are presented. The superconductivity occurs in the vicinity of the Mott insulating state and it is important to clarify the nature of the Mott gap and its doping dependence. Because RIXS has an advantage that we can measure charge excitation in a wide energy-momentum space, it gives a unique opportunity to study the electronic structure of materials. We apply this technique to high-Tc superconducting cuprates. In particular the electronic structure of strongly correlated metals is in the focus of our RIXS study. The experiments were performed at BL11XU of SPring-8, Japan, where a specially designed spectrometer for inelastic x-ray scattering is installed. In optimally doped YBa2Cu3O7-δ, anisotropic spectra are observed in the ab plane of a twin-free crystal. The Mott gap excitation from the one-dimensional CuO chain is enhanced at 2 eV near the zone boundary of the chain direction, while the excitation from the CuO2 plane is broad at 1.5-4 eV and almost independent of momentum. Theoretical calculation based on the one-dimensional and two-dimensional Hubbard model reproduces the observed features in the RIXS spectra when smaller values of the on-site Coulomb energy of the chain than that of the plane are assumed. This means that the charge transfer gap of the chain is smaller than that of the plane. On the other hand, both interband excitation across the Mott gap and intraband excitation in the upper Hubbard band are observed in the electron-doped Nd2-xCexCuO4. The intensity of the interband excitation is concentrated at ˜ 2 eV near the zone boundary while a dispersion relation with a momentum-dependent width emerges in the intraband excitation. The author would like to acknowledge to his collaborators, K. Tsutsui, Y. Endoh, T. Tohyama, K. Kuzushita, T. Inami, K. Ohwada, M. Hoesch, M. Tsubota, Y. Murakami, J. Mizuki, S. Maekawa, T

The effect of temperature cycling typical of low earth orbit satellites on thin films of YBa2Cu3O(7-x)

NASA Technical Reports Server (NTRS)

Mogro-Campero, A.; Turner, L. G.; Bogorad, A.; Herschitz, R.

1991-01-01

Thin films of YBa2Cu3O(7-x) (YBCO) were temperature cycled to simulate conditions of a low earth orbit satellite. In one series of tests, epitaxial and polycrystalline YBCO films were cycled between temperatures of +/- 80 C in vacuum and in nitrogen for hundreds of cycles. The room temperature resistance of an epitaxial YBCO film increased by about 10 percent, but the superconducting transition temperature was unchanged. The largest changes were for a polycrystalline YBCO film on oxidized silicon with a zirconia buffer layer, for which the transition temperature decreased by 3 K. An extended test was carried out for epitaxial films. After 3200 cycles (corresponding to about 230 days in space), transition temperatures and critical current densities remained unchanged.

Epitaxial Growth of YBa2Cu3O7 Films onto LaAlO3 (100) by Using Oxalates

NASA Astrophysics Data System (ADS)

Dominguez, A. Bustamante; Felix, L. León; Garcia, J.; Santibañez, J. Flores; Valladares, L. De Los Santos; Gonzalez, J. C.; Anaya, A. Osorio; Pillaca, M.

Due to the current necessity to obtain epitaxial superconductor films at low cost, we report the growth of YBa2Cu3O7 (Y123) films by chemical deposition. The procedure involved simple steps such as precipitation of stoichiometric amounts of yttrium, barium and copper acetates in oxalic acid (H2C2O4). The precursor solution was dripped onto LaAlO3 (100) substrates with the help of a Fisher pipette. The films were annealed in oxygen atmosphere during 12 h at three different temperatures: 820 °C, 840 °C and 860 °C. After 820 °C and 860 °C annealing, X-ray diffraction (XRD) analysis revealed high intensity of the (00l) reflections denoting that most of the Y123 grains were c-axis oriented. In addition, we also observed a-axis oriented grains ((h00) reflexion), minor randomly oriented grains and other phases (such as Y2BaCuO5 and CuO). In contrast, the sample treated at 840 °C, we noticed c - and a-axis oriented grains, very small amounts of randomly oriented grains without formation of other phases. From the magnetization versus temperature measurements, the critical temperatures were estimated at 70K and 90K for the samples annealed at 820 °C and 860 °C respectively.

Fermi surface measurements in YBa2Cu3O(7-x) and La(1.874)Sr(126)CuO4

NASA Astrophysics Data System (ADS)

Howell, R. H.; Sterne, P. A.; Solal, F.; Fluss, M. J.; Haghighi, H.; Kaiser, J. H.; Rayner, S. L.; West, R. N.; Liu, J. Z.; Shelton, R.

1991-06-01

We report new, ultra high precision measurements of the electron-positron momentum spectra of YBa2Cu3O(7-x) and La(1.874)Sr(126)CuO4. The YBCO experiments were performed on twin free, single crystals and show discontinuities with the symmetry of the Fermi surface of the CuO chain bands. Conduction band and underlying features in LSCO share the same symmetry and can only be separated with the aid of LDA calculations.

Fermi surface measurements in YBa 2Cu 3O 7- x and La 1.874Sr .126CuO 4

NASA Astrophysics Data System (ADS)

Howell, R. H.; Sterne, P. A.; Solal, F.; Fluss, M. J.; Haghight, H.; Kaiser, J. H.; Rayner, S. L.; West, R. N.; Liu, J. Z.; Shelton, R.; Kojima, H.; Kitazawa, K.

1991-12-01

We report new, ultra high precision measurements of the electron-positron momentum spectra of YBa 2Cu 3O 7- x and La 1.874Sr .126CuO 4. The YBCO experiments were performed on twin free, single crystals and show discontinuities with the symmetry of the Fermi surface of the CuO chain bands. Conduction band and underlying features in LSCO share the same symmetry and can only be separated with the aid of LDA calculations.

Epitaxial YBa2Cu3O7-x nanocomposite films and coated conductors from BaMO3 (M = Zr, Hf) colloidal solutions

NASA Astrophysics Data System (ADS)

Obradors, X.; Puig, T.; Li, Z.; Pop, C.; Mundet, B.; Chamorro, N.; Vallés, F.; Coll, M.; Ricart, S.; Vallejo, B.; Pino, F.; Palau, A.; Gázquez, J.; Ros, J.; Usoskin, A.

2018-04-01

Superconducting nanocomposites are the best material choice to address the performance required in power applications and magnets working under high magnetic fields. However, it is still challenging to sort out how to achieve the highest superconducting performance using attractive and competitive manufacturing processes. Colloidal solutions have been recently developed as a novel and very promising low cost route to manufacture nanocomposite coated conductors. Well dispersed and stabilized preformance nanoparticle solutions are first prepared with high concentrations and then mixed with the YBa2Cu3O7 metalorganic precursor solutions to generate colloidal solutions to grow the nanocomposite films. Here we demonstrate, for the first time, that non-reactive BaZrO3 and BaHfO3 perovskite preformed nanoparticles are suitable for growing high quality thin and thick films, and coated conductors with a homogeneous distribution and controlled particle size using this fabrication method. Additionally, we extend the nanoparticle content of the nanocomposites up to 20%-25% mol without any degradation of the superconducting properties. Thick nanocomposite films, up to 0.8 μm, have been prepared with a single deposition of low-fluorine solutions using an ink jet printing dispenser and we demonstrate that the preformed nanoparticles display only a very limited coarsening during the growth process and so high critical current densities J c (B) under high magnetic fields. These films show the highest critical currents achieved so far based on the colloidal solution approach, I c = 220 A/cm-w at 77 K and self-field, and they still have a high potential for further increase in the film thickness. Finally, we also show that nanocomposite YBa2Cu3O7-BaZrO3 coated conductors based on an alternating beam assisted deposited YSZ buffer layer on stainless steel metallic substrates can be developed based on these novel colloidal solutions. Non-reactive preformed oxide perovskite

Phase Evolution of YBa2Cu3O7-x films by all-chemical solution deposition route for coated conductors

NASA Astrophysics Data System (ADS)

Zhao, Yue; Tang, Xiao; Wu, Wei; Grivel, Jean-Claude

2014-05-01

In order to understand the all-chemical-solution-deposition (CSD) processes for manufacturing coated conductors, we investigated the phase evolution of YBa2Cu3O7 (YBCO) films deposited by a low-fluorine metal-organic solution deposition (LF-MOD) method on CSD derived Ce0.9La0.1O2/Gd2Zr2O7/NiW. It is shown that the phase transition from the pyrolyzed film to fully converted YBCO film in the LF-MOD process is similar to that in typical trifluoroacetates-metal organic deposition (TFA-MOD) processes even though the amount of TFA in the solution is reduced by almost one half compared with typical TFA-MOD cases. Moreover, we found that the formation of impurities (mainly BaCeO3, NiWO4 and NiO) is strongly related to the annealing temperature, i.e., the diffusion controlled reactions become intensive from 760 oC, which might be connected with the poor structural and superconducting properties of the films deposited at high sintering temperatures. Based on these results, the optimized growth conditions of YBCO films were established, and a high critical current density (Jc) of about 2 MA/cm2 (77 K, self field) is achieved in a 200 nm thick YBCO film in the architecture made by our all CSD route.

Millimeter-wave surface resistance of laser-ablated YBa2Cu3O(7-delta) superconducting films

NASA Technical Reports Server (NTRS)

Miranda, F. A.; Gordon, W. L.; Bhasin, K. B.; Warner, J. D.

1990-01-01

The millimeter-wave surface resistance of YBa2Cu3O(7-delta) superconducting films was measured in a gold-plated copper host cavity at 58.6 GHz between 25 and 300 K. High-quality laser-ablated films of 1.2-micron thickness were deposited on SrTiO3 and LaGaO3 substrates. Their transition temperatures were 90.0 and 88.9 K, with a surface resistance at 70 K of 82 and 116 milliohms, respectively. These values are better than the values for the gold-plated cavity at the same temperature and frequency.

Transformational dynamics of BZO and BHO nanorods imposed by Y2O3 nanoparticles for improved isotropic pinning in YBa2Cu3O7 -δ thin films

NASA Astrophysics Data System (ADS)

Gautam, Bibek; Sebastian, Mary Ann; Chen, Shihong; Shi, Jack; Haugan, Timothy; Xing, Zhongwen; Zhang, Wenrui; Huang, Jijie; Wang, Haiyan; Osofsky, Mike; Prestigiacomo, Joseph; Wu, Judy Z.

2017-07-01

An elastic strain model was applied to evaluate the rigidity of the c-axis aligned one-dimensional artificial pinning centers (1D-APCs) in YBa2Cu3O7-δ matrix films. Higher rigidity was predicted for BaZrO3 1D-APCs than that of the BaHfO3 1D-APCs. This suggests a secondary APC doping of Y2O3 in the 1D-APC/YBa2Cu3O7-δ nanocomposite films would generate a stronger perturbation to the c-axis alignment of the BaHfO3 1D-APCs and therefore a more isotropic magnetic vortex pinning landscape. In order to experimentally confirm this, we have made a comparative study of the critical current density Jc (H, θ, T) of 2 vol.% BaZrO3 + 3 vol.%Y2O3 and 2 vol.%BaHfO3 + 3 vol.%Y2O3 double-doped (DD) YBa2Cu3O7-δ films deposited at their optimal growth conditions. A much enhanced isotropic pinning was observed in the BaHfO3 DD samples. For example, at 65 K and 9.0 T, the variation of the Jc across the entire θ range from θ=0 (H//c) to θ=90 degree (H//ab) is less than 18% for BaHfO3 DD films, in contrast to about 100% for the BaZrO3 DD counterpart. In addition, lower α values from the Jc(H) ˜ H-α fitting were observed in the BaHfO3 DD films in a large θ range away from the H//c-axis. Since the two samples have comparable Jc values at H//c-axis, the improved isotropic pinning in BaHfO3 DD films confirms the theoretically predicted higher tunability of the BaHfO3 1D-APCs in APC/YBa2Cu3O7-δ nanocomposite films.

High sensitivity of positrons to oxygen vacancies and to copper-oxygen chain disorder in YBa2Cu3O(7-x)

NASA Astrophysics Data System (ADS)

von Stetten, E. C.; Berko, S.; Li, X. S.; Lee, R. R.; Brynestad, J.

1988-05-01

Temperature-dependent positron-electron momentum densities have been studied by two-dimensional angular correlation of annihilation radiation from 10 to 320 K in YBa2Cu3O(7-x) samples. The positron ground-state charge density, computed by the linearized augmented-plane-wave method, indicates that in YBa2Cu3O7 delocalized positrons sample preferentially the linear copper-oxygen chains. Positron localization due to disorder in these chains is invoked to explain the striking differences observed between superconducting (x = about 0.02) and nonsuperconducting (x = about 0.70) samples.

Structural transition of secondary phase oxide nanorods in epitaxial YBa2Cu3O7-δ films on vicinal substrates

NASA Astrophysics Data System (ADS)

Shi, Jack J.; Wu, Judy Z.

2012-12-01

A theoretical study of a structural transition of secondary phase oxide nanorods in epitaxial YBa2Cu3O7-δ films on vicinal SrTiO3 substrates is presented. Two possible types of film/substrate interface are considered, with one assuming complete coherence, while the other is defective as manifested by the presence of antiphase grain boundaries. Only in the former case does the increase of the vicinal angle of the substrate lead to a substantial change of the strain field in the film, resulting in a transition of the nanorod orientation from the normal to the in-plane direction of the film. The calculated threshold vicinal angle for the onset of the transition and lattice deformation of the YBa2Cu3O7-δ film due to the inclusion of the nanorods is in very good agreement with experimental observations. This result sheds lights on the understanding of the role of the film/substrate lattice mismatch in controlling self-assembly of dopant nanostructures in matrix films.

Oxygen desorption from YBa2Cu3O(7-x) and Bi2CaSr2Cu2O(8 + delta) superconductors

NASA Technical Reports Server (NTRS)

Mesarwi, A.; Levenson, L. L.; Ignatiev, A.

1991-01-01

Oxygen desorption experiments from YBa2Cu3O(7-x) (YBCO) and Bi2CaSr2Cu2O(8 + delta) (BSCCO) superconductors were carried out using a quadrupole mass spectrometer for monitoring the desorbing species and X-ray photoemission spectroscopy for surface characterization. Molecular oxygen was found to desorb from both superconductors following photoirradiation with ultraviolet/optical radiation and subsequent heating at over 150 C. Both YBCO and BSCCO were found to have similar oxygen desorption rates and similar activation energies. The desorption data as well as the X-ray photoemission data indicate that the oxygen desorption is not intrinsic to the superconductors but rather due to molecular oxygen entrapped in the material.

Processing-property relations in YBa2Cu3O(6+x) superconductors

NASA Astrophysics Data System (ADS)

Safari, A.; Wachtman, J. B., Jr.; Parkhe, V.; Caracciolo, R.; Jeter, D.

Processing of YBa2Cu3O(6+x) superconducting samples by employing different precursor powder preparation techniques such as ball milling, attrition milling, and narrow particle size distribution powder preparation through coprecipitation by spraying will be discussed. CuO coated with oxalates shows the lowest resistance above Tc up to room temperature. The extent of corrosion by water has been studied by employing magnetic susceptibility, XPS, and X-ray diffraction. Superconducting samples are affected to a considerable extent when treated in water at 60 C and the severity of the attack increases with time.

Influence of γ-Irradiation on the Optical Properties of the Polyimide-YBa2Cu3O6.7 System

NASA Astrophysics Data System (ADS)

Muradov, A. D.; Korobova, N. E.; Kyrykbaeva, A. A.; Yar-Mukhamedova, G. Sh.; Mukashev, K. M.

2018-05-01

Influence of γ-irradiation on the optical properties of a polyimide film and its polymer compositions with fillers of a dispersed powder of a high-temperature superconductor ҮBa2Cu3O6.7 (YBaCuO) with concentrations of 0.05, 0.10, and 0.50 wt.% was studied. It was established that γ-irradiation with a dose up to 600 kGy does not affect the transparency of polyimide films in the visible region of the spectrum. However, at irradiation doses of 250 and 600 kGy, a weakly expressed fine structure appears in the spectra of polyimide films in the range of 220-300 nm due to the contribution of the resulting diene structures to the optical transmission and the increased content of oxygen atoms. The YBaCuO filler and γ-irradiation cause the polyimide transition from the amorphous state to the crystalline state, which is manifested in a sharp change in the spectrum in the range of 2.3-3.9 eV. A significant increase in the extinction coefficient was found in the composite containing 0.50 wt.% of the filler that is associated with an increase in the radius of action of structurally active fillers on the macromolecules of the matrix.

Electronic state and superconductivity of YBa2Cu3-xO7-y (M=Al,Zn and Sn) systems

NASA Technical Reports Server (NTRS)

Zhao, Y.; Zhang, Q. R.; Zhang, H.

1990-01-01

A series of YBa2Cu(3-x)MxO(7-y) (M=Al,Zn and Sn) single phase samples were prepared, and the measurements of the crystal structure, oxygen content, electric resistivity, thermoelectric power, Mossbauer spectrum, XPS and superconductivity were performed. The experimental results of X ray powder diffraction, Mossbauer spectrum and oxygen content show that the Zn(2+) and the Al(3+) occupy the Cu(2) site in Cu-O planes and the Cu(1) site in Cu-O chains respectively, but the Sn(4+) occupies both the Cu(1) sites. As regards the properties in superconducting state, both the Zn(2+) and the Al(3+) depress T(sub c) strongly, but the Sn(4+) does not. As for the electronic transport properties in normal state, the system doped by Al(3+) displays a rapid increase of resistivity and some electron localization-like effects, and the thermoelectric power enhances obviously; the series contained Zn(2+) almost shows no changes of electric resistivity but the sign of the thermoelectric power is reversed. Other results are given and briefly discussed.

Selective interlayer ferromagnetic coupling between the Cu spins in YBa2Cu3O7−x grown on top of La0.7Ca0.3MnO3

PubMed Central

Huang, S. W.; Wray, L. Andrew; Jeng, Horng-Tay; Tra, V. T.; Lee, J. M.; Langner, M. C.; Chen, J. M.; Roy, S.; Chu, Y. H.; Schoenlein, R. W.; Chuang, Y.-D.; Lin, J.-Y.

2015-01-01

Studies to date on ferromagnet/d-wave superconductor heterostructures focus mainly on the effects at or near the interfaces while the response of bulk properties to heterostructuring is overlooked. Here we use resonant soft x-ray scattering spectroscopy to reveal a novel c-axis ferromagnetic coupling between the in-plane Cu spins in YBa2Cu3O7−x (YBCO) superconductor when it is grown on top of ferromagnetic La0.7Ca0.3MnO3 (LCMO) manganite layer. This coupling, present in both normal and superconducting states of YBCO, is sensitive to the interfacial termination such that it is only observed in bilayers with MnO2 but not with La0.7Ca0.3O interfacial termination. Such contrasting behaviors, we propose, are due to distinct energetic of CuO chain and CuO2 plane at the La0.7Ca0.3O and MnO2 terminated interfaces respectively, therefore influencing the transfer of spin-polarized electrons from manganite to cuprate differently. Our findings suggest that the superconducting/ferromagnetic bilayers with proper interfacial engineering can be good candidates for searching the theorized Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) state in cuprates and studying the competing quantum orders in highly correlated electron systems. PMID:26573394

Ten Ghz YBa2Cu3O(7-Delta) Superconducting Ring Resonators on NdGaO3 Substrates

NASA Technical Reports Server (NTRS)

To, H. Y.; Valco, G. J.; Bhasin, K. B.

1993-01-01

YBa2Cu3O(7-delta) thin films were formed on NdGaO3 substrates by laser ablation. Critical temperatures greater than 89 K and critical current densities exceeding 2 x 10(exp 8) Acm(sub -2) at 77 K were obtained. The microwave performance of films patterned into microstrip ring resonators with gold ground planes was measured. An unloaded quality factor six times larger than that of a gold resonator of identical geometry was achieved. The unloaded quality factor decreased below 70 K for both the superconducting and gold resonators due to increasing dielectric losses in the substrate. The temperature dependence of the loss tangent of NdGaO3 was extracted from the measurements.

Theoretical calculations of oxygen relaxation in YBa2Cu3O6+x ceramics

NASA Astrophysics Data System (ADS)

Mi, Y.; Schaller, R.; Sathish, S.; Benoit, W.

1991-12-01

A two-dimensional theoretical model of stress-induced point-defect relaxation in a layered structure is presented, with a detailed discussion of the special case of YBa2Cu3O6+x. The experimental results of oxygen relaxation in YBa2Cu3O6+x can be explained qualitatively by this model.

The effect of fluctuations on the electrical transport behavior in YBa2Cu3O(7-x)

NASA Technical Reports Server (NTRS)

Vitta, Satish; Alterovitz, S. A.; Stan, M. A.

1993-01-01

The excess conductivity behavior of highly oriented YBa2Cu3O(7-x) thin films prepared by both coevaporation and laser ablation was studied in detail in the reduced-temperature range 9 x 10(exp -4) is less than t is less than 1. The excess conductivity in all the films studied was found to diverge sharply near T(sub c), in agreement with the conventional mean-field theory. However, the detailed temperature dependence could not be fitted to either the power-law or the logarithmic functional forms as predicted by the theory. The excess conductivity of all the films was found to be exponentially dependent on the temperature over nearly three decades for 9 x 10(exp -4) is less than t is less than 10(exp -1), in contradiction to the mean-field theory.

Fabrication and characterization of La2Zr2O7 films on different buffer architectures for YBa2Cu3O7-δ coated conductors by RF magnetron sputtering.

PubMed

Xu, Da; Liu, Linfei; Xiao, Guina; Li, Yijie

2013-02-27

La2Zr2O7 (LZO) films were grown on different buffer architectures by radio frequency magnetron sputtering for the large-scale application of YBa2Cu3O7-x (YBCO)-coated conductors. The three different buffer architectures were cerium oxide (CeO2), yttria-stabilized zirconia (YSZ)/CeO2, and CeO2/YSZ/CeO2. The microstructure and surface morphology of the LZO film were studied by X-ray diffraction, optical microscopy, field emission scanning electron microscopy, and atomic force microscopy. The LZO films prepared on the CeO2, YSZ/CeO2, and CeO2/YSZ/CeO2 buffer architectures were preferentially c-axis-oriented and highly textured. The in-plane texture of LZO film on CeO2 single-buffer architecture was ∆ φ = 5.5° and the out-of-plane texture was ∆ ω = 3.4°. All the LZO films had very smooth surfaces, but LZO films grown on YSZ/CeO2 and CeO2/YSZ/CeO2 buffer architectures had cracks. The highly textured LZO film grown on CeO2-seed buffered NiW tape was suitable for the epitaxial growth of YBCO film with high currents.

Atomic layer epitaxy of YBaCuO for optoelectronic applications

NASA Technical Reports Server (NTRS)

Skogman, R. A.; Khan, M. A.; Van Hove, J. M.; Bhattarai, A.; Boord, W. T.

1992-01-01

An MOCVD-based atomic-layer epitaxy process is being developed as a potential solution to the problems of film-thickness and interface-abruptness control which are encountered when fabricating superconductor-insulator-superconductor devices using YBa2Cu3O(7-x). In initial studies, the atomic-layer MOCVD process yields superconducting YBa2Cu3O(7-x) films with substrate temperatures of 605 C during film growth, and no postdeposition anneal. The low temperature process yields a smooth film surface and can reduce interface degradation due to diffusion.

Observation of a three-dimensional quasi-long-range electronic supermodulation in YBa 2Cu 3O 7-x/La 0.7Ca 0.3MnO 3 heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Junfeng; Shafer, Padraic; Mion, Thomas R.

Recent developments in high-temperature superconductivity highlight a generic tendency of the cuprates to develop competing electronic (charge) supermodulations. While coupled with the lattice and showing different characteristics in different materials, these supermodulations themselves are generally conceived to be quasi-two-dimensional, residing mainly in individual CuO 2 planes, and poorly correlated along the c axis. Here we observed with resonant elastic X-ray scattering a distinct type of electronic supermodulation in YBa 2Cu 3O 7–x (YBCO) thin films grown epitaxially on La 0.7Ca 0.3MnO 3 (LCMO). This supermodulation has a periodicity nearly commensurate with four lattice constants in-plane, eight out of plane, withmore » long correlation lengths in three dimensions. It sets in far above the superconducting transition temperature and competes with superconductivity below this temperature for electronic states predominantly in the CuO 2 plane. Our finding sheds light on the nature of charge ordering in cuprates as well as a reported long-range proximity effect between superconductivity and ferromagnetism in YBCO/LCMO heterostructures.« less

Observation of a three-dimensional quasi-long-range electronic supermodulation in YBa 2Cu 3O 7-x/La 0.7Ca 0.3MnO 3 heterostructures

DOE PAGES

He, Junfeng; Shafer, Padraic; Mion, Thomas R.; ...

2016-03-01

Recent developments in high-temperature superconductivity highlight a generic tendency of the cuprates to develop competing electronic (charge) supermodulations. While coupled with the lattice and showing different characteristics in different materials, these supermodulations themselves are generally conceived to be quasi-two-dimensional, residing mainly in individual CuO 2 planes, and poorly correlated along the c axis. Here we observed with resonant elastic X-ray scattering a distinct type of electronic supermodulation in YBa 2Cu 3O 7–x (YBCO) thin films grown epitaxially on La 0.7Ca 0.3MnO 3 (LCMO). This supermodulation has a periodicity nearly commensurate with four lattice constants in-plane, eight out of plane, withmore » long correlation lengths in three dimensions. It sets in far above the superconducting transition temperature and competes with superconductivity below this temperature for electronic states predominantly in the CuO 2 plane. Our finding sheds light on the nature of charge ordering in cuprates as well as a reported long-range proximity effect between superconductivity and ferromagnetism in YBCO/LCMO heterostructures.« less

Chemical durability of high-temperature superconductor YBa2Cu3O(7-x) in aqueous environments

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.; Sandkuhl, Ann L.

1988-01-01

The stability of YBa2Cu3O(7-x) in water and 100-percent humidity has been investigated at three temperatures, using pH measurements, X-ray diffraction, and scanning electron microscopy. The oxide-ceramic superconductor is highly unstable; it reacts rapidly with water and degrades in moisture. Dissolution of the oxide perovskite in water is highly incongruent. The corrosion products are found to be BaCO3, CuO, O2, etc. Barium hydroxide is first formed and further reacts with atmospheric CO2 to form needle-shaped crystals of BaCO3. For any practical applications, devices made from these materials would have to be protected with an impermeable coating to prevent deterioration from atmosphere.

Spectrophotometric Determination of the Hole Concentration in the Superconductor YBa2Cu3O(sub 7-x)

ERIC Educational Resources Information Center

Hoppe, Jack I.; Malati, Mounir A.

2005-01-01

An experimental study of ceramic superconductors namely YBa2Cu3O(sub 7-x), which illustrates the use of spectrophotometry, based on the electronic spectra of complexes of Fe(II), Fe(III) and Cu(II) to better understand the stoichiometry of YBCO is described. The results from this experiment are in good agreement with those obtained by the…

Effects of oxygen stoichiometry on the scaling behaviors of YBa2Cu3O(x) grain boundary weak-links

NASA Technical Reports Server (NTRS)

Wu, K. H.; Fu, C. M.; Jeng, W. J.; Juang, J. Y.; Uen, T. M.; Gou, Y. S.

1995-01-01

The effects of oxygen stoichiometry on the transport properties of the pulsed laser deposited YBa2Cu3O(x) bicrystalline grain boundary weak-link junctions were studied. It is found that not only the cross boundary resistive transition foot structure can be manipulated repeatedly with oxygen annealing processes but the junction behaviors are also altered in accordance. In the fully oxygenated state i.e with x = 7.0 in YBa2Cu3O(x) stoichiometry, the junction critical current exhibits a power of 2 scaling behavior with temperature. In contrast, when annealed in the conditions of oxygen-deficient state (e.g with x = 6.9 in YBa2Cu3O(x) stoichiometry) the junction critical current switches to a linear temperature dependence behavior. The results are tentatively attributed to the modification of the structure in the boundary area upon oxygen annealing, which, in turn, will affect the effective dimension of the geometrically constrained weak-link bridges. The detailed discussion on the responsible physical mechanisms as well as the implications of the present results on device applications will be given.

Room temperature degradation of YBa2Cu3O(7-x) superconductors in varying relative humidity environments

NASA Technical Reports Server (NTRS)

Hooker, M. W.; Wise, S. A.; Carlberg, I. A.; Stephens, R. M.; Simchick, R. T.; Farjami, A.

1993-01-01

An aging study was performed to determine the stability of YBa2Cu3O(7-x) ceramics in humid environments at 20 C. In this study, fired ceramic specimens were exposed to humidity levels ranging from 30.5 to 100 percent for 2-, 4-, and 6-week time intervals. After storage under these conditions, the specimens were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrical resistance measurements. At every storage condition evaluated, the fired ceramics were found to interact with H2O present in the surrounding environment, resulting in the decomposition of the YBa2Cu3O(7-x) phase. XRD data showed that BaCO3, CuO, and Y2BaCuO5 were present after aging and that the peak intensities of these impurity phases increased both with increasing humidity level and with increasing time of exposure. Additionally, SEM analyses of the ceramic microstructures after aging revealed the development of needle-like crystallites along the surface of the test specimens after aging. Furthermore, the superconducting transition temperature T(sub c) was found to decrease both with increasing humidity level and with increasing time of exposure. All the specimens aged at 30.5, 66, and 81 percent relative humidity exhibited superconducting transitions above 80 K, although these values were reduced by the exposure to the test conditions. Conversely, the specimens stored in direct contact with water (100 percent relative humidity) exhibited no superconducting transitions.

Reaction of YBa2Cu3O(7-beta) with Gold, Silver, Bismuth and Lead: Substitution Chemistry and Composite Fabrication

NASA Technical Reports Server (NTRS)

Hepp, Aloysius F.; Gaier, James R.

1993-01-01

The reaction of YBa2Cu3O(7-beta) with Au, Ag, Bi, and Ph ions or metal is described. Three types of materials were produced: a well-defined series of homogeneous superconductors was obtained for Au ion substitution with little effect on T(sub c); attempted Ag and Bi ion substitution resulted in multi-phase samples with slightly enhanced T(sub c); finally, attempts to produce superconducting metal/superconducting ceramic composites with Pb and Bi powders resulted in multi-phase samples with drastically diminished superconducting properties. For Au- substituted superconductors, YBa2(Cu(l-x)Au(x))3O(7-beta), a substitution series (x = 0 - 0.1) has been synthesized. For x = 0.1 there was no change in the a and b lattice parameters (a = 3.826 A and b = 3.889 A) but a 0.06 A c axis expansion to 11.75 A was observed. The valence of Cu and Au in YBa2Au(0.3)Cu(2.7)O(7-beta) was investigated using X-ray Absorption Near-Edge Structure (XANES). X-ray studies indicate that Au goes into the Cu(l) site and Cu K edge XANES shows that this has little effect on the oxidation state of the remaining copper. A small effect on T(sub c) is observed (T(sub c) = 89 K for x = 0.10). Ag and Bi addition results in a rise in T(sub c) and a decrease in (delta)T(sub c) at low levels (x = 0.10 Ag, T(sub c) = 94 K and (delta)T(sub c) = 0.5 K; x = 0.02 Bi, T(sub c) = 94 K and (delta)T(sub c) = 1K) relative to typical values for YBa2Cu3O(7-beta) (T(sub c) = 91 K, (delta)T(sub c) = 2 K). Attempts at fabrication of Pb- and Pb(1-x)Bi(x)-superconductor composites are described. Cold pressing followed by low temperature (200 C) sintering resulted in a composite which excluded flux below 90 K but did not show zero electrical resistance until the metal (alloy) superconducting transition. X-ray diffraction showed the presence of pervoskite and metal. Processing at moderate (450 C) or high (950 C) temperatures resulted in oxygen-depleted pervoskite and/or metal oxides. These materials displayed greatly

Coaxial line configuration for microwave power transmission study of YBa2Cu3O(7-delta) thin films

NASA Technical Reports Server (NTRS)

Chorey, C. M.; Miranda, F. A.; Bhasin, K. B.

1991-01-01

Microwave transmission measurements through YBa2Cu3O(7-delta) (YBCO) high-transition-temperature superconducting thin films on lanthanum aluminate (LaAlO3) have been performed in a coaxial line at 10 GHz. LaAlO3 substrates were ultrasonically machined into washer-shaped discs, polished, and coated with laser-ablated YBCO. These samples were mounted in a 50-ohm coaxial air line to form a short circuit. The power transmitted through the films as a function of temperature was used to calculate the normal state conductivity and the magnetic penetration depth for the films.

Selective interlayer ferromagnetic coupling between the Cu spins in YBa 2Cu 3O 7–x grown on top of La 0.7Ca 0.3MnO 3

DOE PAGES

Huang, S. W.; Wray, L. Andrew; Jeng, Horng -Tay; ...

2015-11-17

Studies to date on ferromagnet/d-wave superconductor heterostructures focus mainly on the effects at or near the interfaces while the response of bulk properties to heterostructuring is overlooked. Here we use resonant soft x-ray scattering spectroscopy to reveal a novel c-axis ferromagnetic coupling between the in-plane Cu spins in YBa 2Cu 3O 7–x (YBCO) superconductor when it is grown on top of ferromagnetic La 0.7Ca 0.3MnO 3 (LCMO) manganite layer. This coupling, present in both normal and superconducting states of YBCO, is sensitive to the interfacial termination such that it is only observed in bilayers with MnO 2 but not withmore » La 0.7Ca 0.3O interfacial termination. Thus, such contrasting behaviors, we propose, are due to distinct energetic of CuO chain and CuO 2 plane at the La 0.7Ca 0.3O and MnO 2 terminated interfaces respectively, therefore influencing the transfer of spin-polarized electrons from manganite to cuprate differently. Our findings suggest that the superconducting/ferromagnetic bilayers with proper interfacial engineering can be good candidates for searching the theorized Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) state in cuprates and studying the competing quantum orders in highly correlated electron systems.« less

Preparation and Physical Properties of Segmented Thermoelectric YBa2Cu3O7-x -Ca3Co4O9 Ceramics

NASA Astrophysics Data System (ADS)

Wannasut, P.; Keawprak, N.; Jaiban, P.; Watcharapasorn, A.

2018-01-01

Segmented thermoelectric ceramics are now well known for their high conversion efficiency and are currently being investigated in both basic and applied energy researches. In this work, the successful preparation of the segmented thermoelectric YBa2Cu3O7-x -Ca3Co4O9 (YBCO-CCO) ceramic by hot pressing method and the study on its physical properties were presented. Under the optimum hot pressing condition of 800 °C temperature, 1-hour holding time and 1-ton weight, the segmented YBCO-CCO sample showed two strongly connected layers with the relative density of about 96%. The X-ray diffraction (XRD) patterns indicated that each segment showed pure phase corresponding to each respective composition. Scanning electron microscopy (SEM) results confirmed the sharp interface and good adhesion between YBCO and CCO layers. Although the chemical analysis indicated the limited inter-layer diffusion near the interface, some elemental diffusion at the boundary was expected to be the source of this strong bonding.

Scanning micro-Hall probe mapping of magnetic flux distributions and current densities in YBa2Cu3O7 thin films

NASA Technical Reports Server (NTRS)

Xing, W.; Heinrich, B.; Zhou, HU; Fife, A. A.; Cragg, A. R.; Grant, P. D.

1995-01-01

Mapping of the magnetic flux density B(sub z) (perpendicular to the film plane) for a YBa2Cu3O7 thin-film sample was carried out using a scanning micro-Hall probe. The sheet magnetization and sheet current densities were calculated from the B(sub z) distributions. From the known sheet magnetization, the tangential (B(sub x,y)) and normal components of the flux density B were calculated in the vicinity of the film. It was found that the sheet current density was mostly determined by 2B(sub x,y)/d, where d is the film thickness. The evolution of flux penetration as a function of applied field will be shown.

Atomic-scale identification of novel planar defect phases in heteroepitaxial YBa2Cu3O7-δ thin films

NASA Astrophysics Data System (ADS)

Gauquelin, Nicolas; Zhang, Hao; Zhu, Guozhen; Wei, John Y. T.; Botton, Gianluigi A.

2018-05-01

We have discovered two novel types of planar defects that appear in heteroepitaxial YBa2Cu3O7-δ (YBCO123) thin films, grown by pulsed-laser deposition (PLD) either with or without a La2/3Ca1/3MnO3 (LCMO) overlayer, using the combination of high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging and electron energy loss spectroscopy (EELS) mapping for unambiguous identification. These planar lattice defects are based on the intergrowth of either a BaO plane between two CuO chains or multiple Y-O layers between two CuO2 planes, resulting in non-stoichiometric layer sequences that could directly impact the high-Tc superconductivity.

Microscopic adaptation of BaHfO3 and Y2O3 artificial pinning centers for strong and isotropic pinning landscape in YBa2Cu3O7-x thin films

NASA Astrophysics Data System (ADS)

Gautam, Bibek; Sebastian, Mary Ann; Chen, Shihong; Haugan, Timothy; Zhang, Wenrui; Huang, Jijie; Wang, Haiyan; Wu, Judy Z.

2018-07-01

A study of 3 vol% Y2O3 + 2-6 vol% BaHfO3 double-doped YBa2Cu3O7-x (BHO DD) epitaxial thin films was carried out to explore the morphology adaption of c-axis aligned one-dimensional BHO artificial pinning centers (1D APCs) to secondary Y2O3 nanoparticles (3D APCs). BHO 1D APCs have been predicted to have the least rigidity in an elastic strain energy model in APC/YBa2Cu3O7-x nanocomposite films. Consequently, they could be best ‘tuned’ away from the c-axis alignment by local strains generated by the Y2O3 3D APCs. This provides an opportunity to generate mixed-morphology APCs, especially at high BHO concentrations. Motivated by this, we have carried out a systematic study of the transport critical current density J c(H, T, θ) on the BHO DD samples in magnetic fields (H) up to 90 kOe at different H orientations from H//c-axis (θ = 0), to θ = 45°, and to H//ab-plane (θ = 90°). Enhanced pinning at all three orientations was observed as illustrated in the comparable low alpha (α) values in the range of 0.13-0.25 at 65 K, which is consistent with the mixed 1D (in c-axis) + 2D (in ab-plane) + 3D APCs observed in transmission electron microscopy (TEM). Upon increasing BHO concentration from 2 to 4 vol%, a monotonic increase of the accommodation field H* at θ = 0°, 45° and 90° was observed, indicative of the APC concentration increase of the mixed morphologies. At 6 vol% BHO, the H* continues the increase to 85 kOe at H//c-axis (θ = 0), and >90 kOe H//ab-plane (θ = 90°), while it decreases from 80 to 85 kOe at 2-4 vol% to 60 kOe at 6 vol% at θ = 45°, which is consistent with the TEM observation of the connection of 3D APCs, appeared at lower BHO concentration into 2D ones in ab-plane at the higher BHO concentrations. These results shed light on the quantitative adaptation of APCs of mixed morphologies with increasing BHO doping in the BHO DD thin films and are important for controlling the APC pinning landscape towards minimal angular dependence.

Method for preparation of textured YBa.sub.2 Cu.sub.3 O.sub.x superconductor

DOEpatents

Selvamanickam, Venkat; Goyal, Amit; Kroeger, Donald M.

1998-01-01

The present invention relate to textured YBa.sub.2 Cu.sub.3 O.sub.x (Y-123) superconductors and a process of preparing them by directional recrystallization of compacts fabricated from quenched YBCO powders at temperatures about 100.degree. C. below the peritectic temperature to provide a superconductor where more than 75% of the YBa.sub.2 Cu.sub.3 O.sub.x phase is obtained without any Y.sub.2 BaCuO.sub.5 .

Influence of calcium on transport properties, band spectrum and superconductivity of YBa2Cu3O(y) and YBa(1.5)La(0.5)Cu3O(y)

NASA Technical Reports Server (NTRS)

Gasumyants, V. E.; Vladimirskaya, E. V.; Patrina, I. B.

1995-01-01

The comparative investigation of transport phenomena in Y(1-x)Ca(x)Ba2Cu3O(y) (0 is less than x is less than 0.25; 6.96 is greater than y is greater than 6.87 and 6.73 is less than x is less than 6.53); Y(1-x)Ca(x)Ba(1.5)La(0.5)Cu3O(y) (0 is less than x is less than 0.5; 7.12 is greater than y is greater than 6.96) and YBa(2-x)La(x)Cu3O(y) (0 is less than x is less than 0.5; 6.95 is less than y is less than 7.21) systems have been carried out. The temperature dependencies of resistivity and thermopower have been measured. It was found that the S(T) dependencies take some additional features with Ca content increase. The results obtained have been analyzed on the basis of the phenomenological theory of electron transport in the case of the narrow conductive band. The main parameters of the band spectrum (the band filling with electrons degree and the total effective band width) have been determined. The dependencies of these from contents of substituting elements are discussed. Analyzing the results obtained simultaneously with the tendencies in oxygen content and critical temperature change we have confirmed the conclusion that the oxygen sublattice disordering has a determinant effect on band structure parameters and superconductive properties of YBa2Cu3O(y). The results obtained suggest that Ca gives rise to some peculiarities in band spectrum of this compound.

Low-pressure large-area magnetron sputter deposition of YBa2Cu3O7-δ films for industrial applications

NASA Astrophysics Data System (ADS)

Wördenweber, Roger; Hollmann, Eugen; Poltiasev, Michael; Neumüller, Heinz-Werner

2003-05-01

This paper addresses the development of a technically relevant sputter-deposition process for YBa2Cu3O7-delta films. First, the simulation of the particle transport from target to substrate indicates that only at a reduced pressure of p approx 1-10 Pa can a sufficiently large deposition rate and homogeneous stoichiometric distribution of the particles during large-area deposition be expected. The results of the simulations are generally confirmed by deposition experiments on CeO2 buffered sapphire and LaAlO3 substrates using a magnetron sputtering system suitable for large-area deposition. However, it is shown that in addition to the effect of scattering during particle transport, the conditions at the substrate lead to a selective growth of Y-Ba-Cu-O phases that, among others, strongly affect the growth rate. For example, the growth rate is more than three times larger for optimized parameters compared to the same set of parameters but at 100 K lower substrate temperature. Stoichiometrical and structural perfect films can be grown at low pressure (p < 10 Pa). However, the superconducting transition temperature of these films is reduced. The Tc reduction seems to be correlated with the c-axis length of YBa2Cu3O7-delta. Two possible explanations for the increased c-axis length and the correlated reduced transition temperature are discussed, i.e. reduced oxygen content and strong cation site disorder due to the heavy particle bombardment.

Secondary ion mass spectroscopy study of Au trapping and migration in the Au-irradiated YBa2Cu3O7 - delta film

NASA Astrophysics Data System (ADS)

Li, Yupu; Kilner, J. A.; Liu, J. R.; Chu, W. K.; Wagner, G. A.; Somekh, R. E.

1996-05-01

The range data and migration of Au in YBa2Cu3O7-δ film were studied with implanted 197Au (1.5 MeV 5×1015 Au+/cm2) as a tracer. The film was a c-axis oriented film, ˜750 nm thick, deposited by high-pressure planar dc sputtering on <100> LaAlO3. Analysis by secondary ion mass spectroscopy shows that the as-implanted Au concentration distribution is essentially Gaussian-like and the depth (R̂p) of maximum Au concentration (˜1.2 wt %) is 201 nm. The projected range (R¯p) and (R̂p) are found to be in very good agreement with the simulated data by TRIM-95, whereas the measured ``straggle'' (ΔRp*) is about 20% larger than that by TRIM-95 simulation. It has also been found that the implanted 197Au starts to migrate within the film at a temperature between 650 and 700 °C, which is much higher than that for the implanted 2H (˜175 °C) and the implanted 18O (between 250 and 300 °C) in c-oriented YBa2Cu3O7-δ films.

Environment-resistive coating for the thin-film-based superconducting fault-current limiter Ag/Au-Ag/YBa 2Cu 3O 7/CeO 2/Al 2O 3

NASA Astrophysics Data System (ADS)

Matsui, H.; Kondo, W.; Tsukada, K.; Sohma, M.; Yamaguchi, I.; Kumagai, T.; Manabe, T.; Arai, K.; Yamasaki, H.

2010-02-01

We have studied environment-resistive coatings (ERC) for the thin-film-based superconducting fault-current limiter (SFCL) Ag/Au-Ag/YBa 2Cu 3O 7/CeO 2/Al 2O 3. We evaluated nine candidate ERC materials by two accelerating-environment tests, and revealed that the shellac- and the fluorine-resin have a high environmental resistance. Especially, the shellac resin almost completely protected Jc of an element exposed to 60 °C saturated water vapor for 2 h (3.4->3.2 MA/cm 2). We also performed a practical operation test of SFCL using an element half covered by shellac, and found that the ERC does not diminish the current limiting properties similarly to the previous results of the Teflon-coated SFCL [1].

Synthesis and characterization of YBaCu2O5-δ compound

NASA Astrophysics Data System (ADS)

Ehsandoust, A.; Sandoghchi, M.; Mokhtari, P.; Akhavan, M.

2018-05-01

YBaCu2O5 compound as one of the possible microstructures of Y3Ba5Cu8O19 has been synthesized. The X-ray diffraction analysis of this compound indicates that its formation is accompanied with the formation of YBa2Cu3O7-δ. The observed superconductivity around ∼92 K supports this. So, it seems that YBa2Cu3O7-δ is responsible for the observed superconductivity in YBaCu2O5, and this phase is not an independent superconducting phase. Consequently, the overall effect of the YBaCu2O5 formation during the Y3Ba5Cu8O19 fabrication process could be a reduction in Tc.

Critical current density enhancement by phase decomposition of YBa 2Cu 4O 8 into YBa 2Cu 3O 7-σ and CuO

NASA Astrophysics Data System (ADS)

Krelaus, J.; Heinemann, K.; Ullmann, B.; Freyhardt, H. C.

1995-02-01

Bulk YBa 2Cu 4O 8 (Y-124) is prepared from YBa 2Cu 3O 7-σ (Y-123) and CuO by a powder-metallurgical method. The superconducting features of the Y-124, in particular critical current densities and activation energies, are measured resistively using a four-probe technique and magnetically using a Faraday magnetometer. In a second step the Y-124 is decomposed at high temperatures. The intragranular critical current density is measured at different annealing times, tA, in order to determine and discuss the characteristics of the jc( tA) curves.

Geometric and compositional factors on critical current density in YBa2Cu3O7‑δ films containing nanorods

NASA Astrophysics Data System (ADS)

Horide, Tomoya; Nagao, Sho; Izutsu, Ryosuke; Ishimaru, Manabu; Kita, Ryusuke; Matsumoto, Kaname

2018-06-01

Critical current density (J c) was investigated in YBa2Cu3O7‑δ films containing nanorods prepared with various nanorod materials, with variation of nanorod content, substrate temperature, and oxidization condition. Three types of compositional situation were realized: films containing strain induced oxygen vacancies; fully oxidized films containing cation compositional deviation; and oxygen deficient films. Normalized J c‑B behavior was determined via the matching field, which is a geometric factor, regardless of the compositional details. A J c‑critical temperature (T c) relation depending on distribution and fraction of compositional deviation (cation compositional deviation and strain induced oxygen vacancies) was found: the J c values decreased with decreasing T c due to the effect of T c on nanorod pinning strength in the fully oxidized films; J c decreased with decreasing oxygen pressure in the film cooling process after film deposition in spite of T c remaining almost the same, due to reduction of the effective area for current flow in the oxygen deficient films. Thus, a J c landscape based on geometric and compositional factors was obtained. The study highlights the importance of the J c‑T c analysis in the understanding of J c in YBa2Cu3O7‑δ films containing nanorods.

Positron annihilation study of Y 1- xPr xBa 2Cu 3O 7

NASA Astrophysics Data System (ADS)

Zhao, Y. G.; Cao, B. S.; Yu, W. Z.; Du, Z. H.; Wang, Y. J.; Luo, C. Y.; Hu, H.; Wang, S.; Yang, J. H.; He, A. S.; Gu, B. L.

1995-02-01

A positron annihilation study of Y 1- xPr xBa 2Cu 3O 7 was performed. The results showed that charge transfer between the CuO 2 planes and 1D CuO chains upon Pr doping, as proposed in the literature, did not occur. Pr doping suppressed the anomaly of positron annihilation lifetime near and below Tc which has been observed in YBa 2Cu 3O 7. The perfection of the 1D CuO chains was reduced by Pr doping and this may be partly responsible for the increase of resistivity with Pr doping, and finally the semiconducting behaviour of DC resistivity in Y 1- xPr xBa 2Cu 3O 7 with x > 0.6.

Study of Substitution of Zn FOR Cu in YBa2Cu3O7 System

NASA Astrophysics Data System (ADS)

Sharma, P. K.; Samariya, A.; Dhawan, M. S.; Singhal, R. K.

The polycrystalline YBa2(Cu1-XZnX)3O7-δ samples (x=0.0 to 0.06) were synthesized and studied using X Ray diffraction, titration, resistivity, magnetization and X ray photoelectron spectroscopy (XPS). Results show that O2 stoichiometry (δ) changes on Zn substitution which affects their normal state resistivity as well as the TC. Zn also induces local magnetic moment as evidenced from magnetization results. A combination of change in O2 stoichiometry and magnetic pair breaking is found to be responsible for a rapid suppression of superconductivity.

Shear at Twin Domain Boundaries in YBa2Cu3O7-x

NASA Astrophysics Data System (ADS)

Caldwell, W. A.; Tamura, N.; Celestre, R. S.; MacDowell, A. A.; Padmore, H. A.; Geballe, T. H.; Koster, G.; Batterman, B. W.; Patel, J. R.

2004-05-01

The microstructure and strain state of twin domains in YBa2Cu3O7-x are discussed based upon synchrotron white-beam x-ray microdiffraction measurements. Intensity variations of the fourfold twin splitting of Laue diffraction peaks are used to determine the twin domain structure. Strain analysis shows that interfaces between neighboring twin domains are strained in shear, whereas the interior of these domains are regions of low strain. These measurements are consistent with the orientation relationships of twin boundaries within and across domains and show that basal plane shear stresses can exceed 100MPa where twin domains meet. Our results support stress field pinning of magnetic flux vortices by twin domain boundaries.

Bulk modulus and its pressure derivative of YBa2Cu3O7-x

NASA Astrophysics Data System (ADS)

Cankurtaran, M.; Saunders, G. A.; Willis, J. R.; Al-Kheffaji, A.; Almond, D. P.

1989-02-01

Pressure dependences of the ultrasonic wave velocities in polycrystalline YBa2Cu3O7-x are reported. Porosity effects are taken into account using wave-scattering theory in a porous medium. The bulk modulus B0 at atmospheric pressure for the nonporous matrix is 65 GPa, much smaller than B(P) obtained at high pressures from lattice-parameter measurements. This discrepancy accrues from the large value of (∂B/∂P). The comparatively small B0 and large (∂B/∂P) are due to vacant anion sites in this defect perovskite.

Effect of Load-Induced Oxygen Absorption in YBa2Cu3O6 + x on Mechanical Properties of the "Polyimide-YBa2Cu3O6 + x " System

NASA Astrophysics Data System (ADS)

Muradov, A. D.; Kyrykbaeva, A. A.

2018-05-01

We have studied the effect of oxygen absorption by disperse powder fillers made of high-temperature superconductor YBa2Cu3O6 + x (YBCO) with concentrations of 0.05, 0.1, and 0.5 mass % on mechanical properties of polyimide composite materials (PCMs) in the form of films. It has been established that an adsorption boundary layer consisting of an aggregate of several transition layers with a varying structure is formed between filler particles and the matrix. A sharp increase in relative elongation (strain) Δɛ c , which is observed for a PCM with YBCO fillers in the form of a jump in the region of loads of 40-47 MPa, is due to the fact that the bonds between the matrix macromolecules and the molecules in the vicinity of the upper boundary layer are ruptured, leading to a strain jump. An increase in the filler concentration increases the rigidity of the bonds between macromolecules in the boundary layers, leads to a shift of Δɛ c to the region of low stresses, and reduces its value.

Crystalline orientation engineering and charge transport in thin film YBa(2)Cu(3)O(7-x) superconducting surface-coated conductors

NASA Astrophysics Data System (ADS)

Chudzik, Michael Patrick

The weak-link behavior of grain boundaries in polycrystalline high-T c superconductors adversely affects the current density in these materials. The development of wire technology based on polycrystalline high-Tc materials requires understanding and controlling the development of low-angle grain boundaries in these conductors. The research goal is to comprehensively examine the methodology in fabrication and characterization to understand the structure-transport correlation in YBa2Cu3O 7-x (YBCO) surface-coated conductors. High current density YBCO coated conductors were fabricated and characterized as candidates for second generation high-Tc wire technology. Critical current densities (Jc) greater than 1 x 106 A/cm2 at 77 K and zero magnetic field were obtained using thin films epitaxially grown by metalorganic chemical vapor deposition (MOCVD) and pulsed laser deposition (PLD) on oriented buffer layers. The biaxially textured oxide buffer layers were deposited by ion-beam-assisted deposition (IBAD). The transport properties of coated conductors were evaluated in high magnetic fields for intrinsic and extrinsic flux vortex pinning effects for improved high-field properties. Transport Jc's of these coated conductors at 7 tesla (77 K) were measured at values greater than 105 A/cm 2 with the magnetic field perpendicular to the YBCO c-axis (B⊥ c) in both MOCVD and PLD derived conductors. The Jc's in B || c orientation fell an order of magnitude lower at 7 tesla to values near 10 4 A/cm2 due to decreased intrinsic flux pinning. The critical current densities as a function of grain boundary misorientation were found to deviate from the general trend determined for single grain boundary junctions, due to the mosaic structure, which allows meandering current flow. Extensive parametric investigations of relevant thin film growth techniques were utilized to establish growth-property relationships that led to optimized fabrication of high-Tc conductors. The work contained

Strongly suppressed proximity effect and ferromagnetism in topological insulator/ferromagnet/superconductor thin film trilayers of Bi2Se3/SrRuO3/underdoped YBa2Cu3O x : a possible new platform for Majorana nano-electronics

NASA Astrophysics Data System (ADS)

Koren, Gad

2018-07-01

We report properties of a topological insulator–ferromagnet–superconductor trilayers comprised of thin films of 20 nm thick {Bi}}2{Se}}3 on 10 nm SrRuO3 on 30 nm {YBa}}2{Cu}}3{{{O}}}x. As deposited trilayers are underdoped and have a superconductive transition with {{T}}{{c}} onset at 75 K, zero resistance at 65 K, {{T}}Cueri} at 150 K and {{T}}* of about 200 K. Further reannealing under vacuum yields the 60 K phase of {YBa}}2{Cu}}3{{{O}}}x which still has zero resistance below about 40 K. Only when 10 × 100 microbridges were patterned in the trilayer, some of the bridges showed resistive behavior all the way down to low temperatures. Magnetoresistance versus temperature of the superconductive ones showed the typical peak due to flux flow against pinning below {{T}}{{c}}, while the resistive ones showed only the broad leading edge of such a peak. All this indicates clearly weak-link superconductivity in the resistive bridges between superconductive {YBa}}2{Cu}}3{{{O}}}x grains via the topological and ferromagnetic cap layers. Comparing our results to those of a reference trilayer (RTL) with the topological {Bi}}2{Se}}3 layer substituted by a non-superconducting highly overdoped {La}}1.65{Sr}}0.35{CuO}}4, indicates that the superconductive proximity effect as well as ferromagnetism in the topological trilayer are actually strongly suppressed compared to the non-topological RTL. This strong suppression could originate in lattice and Fermi levels mismatch as well as in short coherence length and unfavorable effects of strong spin–orbit coupling in {Bi}}2{Se}}3 on the d-wave pairing of {YBa}}2{Cu}}3{{{O}}}x. Proximity induced edge currents in the SRO/YBCO layer could lead to Majorana bound states, a possible signature of which is observed in the present study as zero bias conductance peaks.

Characteristics of YBa2Cu3O7 high-Tc superconductor with KCl

NASA Astrophysics Data System (ADS)

Yoon, Ki Hyun; Chang, Sung Sik

1990-03-01

The lattice parameters, microstructural change, transition temperature, and electrical properties of the YBa2-xKxCu3O7 high-Tc superconductor in the range from x=0 to x=0.25 have been investigated. The high-Tc orthorhombic phase increases with increasing KCl up to x=0.20, above which it decreases. The lattice parameters decrease with increasing KCl up to x=0.10, and then become nearly uniform. The grain size increases with increasing KCl up to x=0.20 due to its role as sintering agent. The specimens with x=0.2 have transition temperatures of 96 K and high magnetic susceptibility due to the contraction of lattice parameters a and b and the increase of orthorhombic distortion.

Disentangling vortex pinning landscape in chemical solution deposited superconducting YBa2Cu3O7-x films and nanocomposites

NASA Astrophysics Data System (ADS)

Palau, A.; Vallès, F.; Rouco, V.; Coll, M.; Li, Z.; Pop, C.; Mundet, B.; Gàzquez, J.; Guzman, R.; Gutierrez, J.; Obradors, X.; Puig, T.

2018-07-01

In-field angular pinning performances at different temperatures have been analysed on chemical solution deposited (CSD) YBa2Cu3O7-x (YBCO) pristine films and nanocomposites. We show that with this analysis we are able to quantify the vortex pinning strength and energies, associated with different kinds of natural and artificial pinning defects, acting as efficient pinning centres at different regions of the H-T phase diagram. A good quantification of the variety of pinning defects active at different temperatures and magnetic fields provides a unique tool to design the best vortex pinning landscape under different operating conditions. We have found that by artificially introducing a unique defect in the YBCO matrix, the stacking faults, we are able to modify three different contributions to vortex pinning (isotropic-strong, anisotropic-strong, and isotropic-weak). The isotropic-strong contribution, widely studied in CSD YBCO nanocomposites, is associated with nanostrained regions induced at the partial dislocations surrounding the stacking faults. Moreover, the stacking fault itself acts as a planar defect which provides a very effective anisotropic-strong pinning at H//ab. Finally, the large presence of Cu-O cluster vacancies found in the stacking faults have been revealed as a source of isotropic-weak pinning sites, very active at low temperatures and high fields.

Transport properties of ultrathin YBa2Cu3O7 -δ nanowires: A route to single-photon detection

NASA Astrophysics Data System (ADS)

Arpaia, Riccardo; Golubev, Dmitri; Baghdadi, Reza; Ciancio, Regina; Dražić, Goran; Orgiani, Pasquale; Montemurro, Domenico; Bauch, Thilo; Lombardi, Floriana

2017-08-01

We report on the growth and characterization of ultrathin YBa2Cu3O7 -δ (YBCO) films on MgO (110) substrates, which exhibit superconducting properties at thicknesses down to 3 nm. YBCO nanowires, with thicknesses down to 10 nm and widths down to 65 nm, have also been successfully fabricated. The nanowires protected by a Au capping layer show superconducting properties close to the as-grown films and critical current densities, which are limited by only vortex dynamics. The 10-nm-thick YBCO nanowires without the Au capping present hysteretic current-voltage characteristics, characterized by a voltage switch which drives the nanowires directly from the superconducting to the normal state. We associate such bistability to the presence of localized normal domains within the superconductor. The presence of the voltage switch in ultrathin YBCO nanostructures, characterized by high sheet resistance values and high critical current values, makes our nanowires very attractive devices to engineer single-photon detectors.

TOPICAL REVIEW: Importance of low-angle grain boundaries in YBa2Cu3O7-δ coated conductors

NASA Astrophysics Data System (ADS)

Durrell, J. H.; Rutter, N. A.

2009-01-01

Over the past ten years the perception of grain boundaries in YBa2Cu3O7-δ conductors has changed greatly. They are now not a problem to be eliminated, but an inevitable and potentially favourable part of the material. This change has arisen as a consequence of new manufacturing techniques which result in excellent grain alignment, reducing the spread of grain boundary misorientation angles. At the same time there is considerable recent evidence which indicates that the variation of properties of grain boundaries with mismatch angle is more complex than a simple exponential decrease in critical current. This is due to the fact that low-angle grain boundaries represent a qualitatively different system to high-angle boundaries. The time is therefore right for a targeted review of research into low-angle YBa2Cu3O7-δ grain boundaries. This article does not purport to be a comprehensive review of the physics of grain boundaries as found in YBa2Cu3O7-δ in general; for a broader overview we would recommend that the reader consult the comprehensive review of Hilgenkamp and Mannhart (2002 Rev. Mod. Phys. 74 485). The purpose of this article is to review the origin and properties of the low-angle grain boundaries found in YBa2Cu3O7-δ coated conductors both individually and as a collective system.

Temperature dependence of superfluid density in YBa 2Cu 3O 7- δ and Y 0.7Ca 0.3Ba 2Cu 3O 7- δ thin films: A doping dependence study of the linear slope

NASA Astrophysics Data System (ADS)

Lai, L. S.; Juang, J. Y.; Wu, K. H.; Uen, T. M.; Gou, Y. S.

2005-11-01

By using a microstrip ring resonator to measure the temperature dependence of the in-plane magnetic penetration depth λ(T) in YBa2Cu3O7-δ (YBCO) and Y0.7Ca0.3Ba2Cu3O7-δ (Ca-YBCO) epitaxially grown thin films, the linear temperature dependence of the superfluid density ρs/m∗ ≡ 1/λ2(T) was observed from the under- to the overdoped regime at the temperatures below T/Tc ≈ 0.3 . For the underdoped regime of YBCO and Ca-YBCO thin films, the magnitude of the slope d(1/λ2(T))/dT is insensitive to doping, and it can be treated in the framework of projected d-density-wave model. Combining these slope values with the thermal conductivity measurements, the Fermi-liquid correction factor α2 from the Fermi-liquid model, suggested by Wen and Lee, was revealed here with various doping levels.

Microwave Conductivity of Laser Ablated YBa2Cu3O7-delta Superconducting Films and Its Relation to Microstrip Transmission Line Performance

NASA Technical Reports Server (NTRS)

Bhasin, K. B.; Warner, J. D.; Chorey, C. M.; Ebihara, B. T.; Romanofsky, R. R.; Heinen, V. O.

1990-01-01

We report on the values of the microwave conductivity in the normal (sigma(subN)) and superconducting (sigma*=sigma(sub1)-j sigma(sub2)) states of two laser ablated YBa2CU3O7(sigma) thin films at 35 GHz, in the temperature range from 20 to 300 K. The films 0.7 and 0.4 micrometers) were deposited on LaA10(sub3) by laser ablation. The conductivity was obtained from the microwave power transmitted through the films and assuming a two-fluid model. Values of sigma(subN) approximately 2.3 X 10(exp5) S/m at room temperature for both films, and of sigma(sub1) approximately 6.3 X 10(exp5) and 4.6 X 10(exp5) S/m at temperatures around 80 K were obtained for the 0.7 and 0.4 micrometer films respectively. For sigma(sub2) values of 4.9 X 10(exp6) and 5.4 X 10(exp6) S/m were obtained for the 0.7 and 0.4 micrometer films at 80 K. The expected conductor losses and Q-factor of a superconducting ring resonator were calculated using these conductivity values. The theoretical values were then compared with the experimental results obtained for a resonator fabricated from one of these films.

Method of producing superconducting fibers of YBa[sub 2]Cu[sub 3]O[sub x

DOEpatents

Schwartzkopf, L.A.; Ostenson, J.E.; Finnemore, D.K.

1990-11-13

Fibers of YBa[sub 2]Cu[sub 3]O[sub x] have been produce by pendant drop melt extraction. This technique involves the end of a rod of YBa[sub 2]Cu[sub 3]O[sub x] melted with a hydrogen-oxygen torch, followed by lowering onto the edge of a spinning wheel. The fibers are up to 10 cm in length with the usual lateral dimensions, ranging from 20 [mu]m to 125 [mu]m. The fibers require a heat treatment to make them superconducting.

Impact of oxygen diffusion on superconductivity in YBa2Cu3O7 -δ thin films studied by positron annihilation spectroscopy

NASA Astrophysics Data System (ADS)

Reiner, M.; Gigl, T.; Jany, R.; Hammerl, G.; Hugenschmidt, C.

2018-04-01

The oxygen deficiency δ in YBa2Cu3O7 -δ (YBCO) plays a crucial role for affecting high-temperature superconductivity. We apply (coincident) Doppler broadening spectroscopy of the electron-positron annihilation line to study in situ the temperature dependence of the oxygen concentration and its depth profile in single crystalline YBCO film grown on SrTiO3 (STO) substrates. The oxygen diffusion during tempering is found to lead to a distinct depth dependence of δ , which is not accessible using x-ray diffraction. A steady state reached within a few minutes is defined by both, the oxygen exchange at the surface and at the interface to the STO substrate. Moreover, we reveal the depth-dependent critical temperature Tc in the as prepared and tempered YBCO film.

Effects of oxygen stoichiometry on the scaling behaviors of YBa{sub 2}Cu{sub 3}O{sub x} grain boundary weak-links

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, K.H.; Fu, C.M.; Jeng, W.J.

1994-12-31

The effects of oxygen stoichiometry on the transport properties of the pulsed laser deposited YBa{sub 2}Cu{sub 3}O{sub x} bicrystalline grain boundary weak-link junctions were studied. It is found that not only the cross boundary resistive transition foot structure can be manipulated repeatedly with oxygen annealling processes but the junction behaviors are also altered in accordance. In the fully oxygenated state i.e. with x=7.0 in YBa{sub 2}Cu{sub 3}O{sub x} stoichiometry, the junction critical current exhibits a power of 2 scaling behavior with temperature. In contrast, when annealed in the conditions of oxygen-deficient state (e.g. with x=6.9 in YBa{sub 2}Cu{sub 3}O{sub x}more » stoichiometry) the junction critical current switches to a linear temperature dependence behavior. The results are tentatively attributed to the modification of the structure in the boundary area upon oxygen annealing, which, in turn, will affect the effective dimension of the geometrically constrained weak-link bridges. The detailed discussion on the responsible physical mechanisms as well as the implications of the present results on device applications will be given.« less

Magnetic penetration depth of YBa2Cu3O(7-delta) thin films determined by the power transmission method

NASA Technical Reports Server (NTRS)

Heinen, Vernon O.; Miranda, Felix A.; Bhasin, Kul B.

1992-01-01

A power transmission measurement technique was used to determine the magnetic penetration depth (lambda) of YBa2Cu3O(7-delta) superconducting thin films on LaAlO3 within the 26.5 to 40.0 GHz frequency range, and at temperatures from 20 to 300 K. Values of lambda ranging from 1100 to 2500 A were obtained at low temperatures. The anisotropy of lambda was determined from measurements of c-axis and a-axis oriented films. An estimate of the intrinsic value of lambda of 90 +/- 30 nm was obtained from the dependence of lambda on film thickness. The advantage of this technique is that it allows lambda to be determined nondestructively.

Thickness effect of Gd2Zr2O7 buffer layer on performance of YBa2Cu3O7-δ coated conductors

NASA Astrophysics Data System (ADS)

Qiu, Wenbin; Fan, Feng; Lu, Yuming; Liu, Zhiyong; Bai, Chuanyi; Guo, Yanqun; Cai, Chuanbing

2014-12-01

Bilayer buffer architecture of Gd2Zr2O7 (GZO)/Y2O3 was prepared on the biaxially textured tape of Ni-5 at% W (NiW) by reactive sputtering deposition technique. The buffer layer of GZO films were deposited with different thicknesses on Y2O3 seeding layer with a given thickness of 20 nm. According to the results of φ-scan, the in-plane FWHMs of GZO films decreased and then reversed with increasing thickness of GZO, which corresponded with the in-plane FWHMs and superconducting properties of YBa2Cu3O7-δ (YBCO) films. Reflection High-Energy Electron Diffraction (RHEED) was carried out to examine the surface texture of GZO films and the deteriorated surface alignment was found for thicker films. The thickness effect of GZO on performance of YBCO is the coupling result of surface texture and blocking effect caused by thickness. With the balance of these two factors, the YBCO/GZO(120 nm)/Y2O3/NiW architecture exhibit relatively high performance with the transition temperature Tc of 92 K, a transition width ΔTc below 1 K, and a critical current density Jc of 0.65 MA/cm2.

A two-dimensional ACAR study of untwinned YBa2Cu3O(7-x)

NASA Astrophysics Data System (ADS)

Smedskjaer, L. C.; Bansil, A.

1991-12-01

We have carried out 2D-ACAR measurements on an untwinned single crystal of YBa2Cu3O(sub 7-x) as a function of temperature, for five temperatures ranging from 30K to 300K. We show that these temperature-dependent 2D-ACAR spectra can be described to a good approximation as a superposition of two temperature independent spectra with temperature-dependent weighting factors. We show further how the data can be used to correct for the 'background' in the experimental spectrum. Such a 'background corrected' spectrum is in remarkable accord with the corresponding band theory predictions, and displays, in particular, clear signatures of the electron ridge Fermi surface.

Vibrational spectra and lattice instabilities in the high-Tc superconductors YBa2Cu3O7 and GdBa2Cu3O7

NASA Astrophysics Data System (ADS)

Bozović, I.; Mitzi, D.; Beasley, M.; Kapitulnik, A.; Geballe, T.; Perkowitz, S.; Carr, G. L.; Lou, B.; Sudharsanan, R.; Yom, S. S.

1987-09-01

The exceptionally high Tc of layered cuprates was proposed recently as originating from electronically driven structural instabilities. We have studied the infrared and Raman spectra of YBa2Cu3O7-δ and GdBa2Cu3O7-δ over a broad range of temperatures, from 10 to 300 K. We observed neither mode softening nor any other spectroscopic signature of lattice instabilities.

Quasiparticle properties at microwave frequencies in the underdoped YBa2Cu3O7-δ thin films

NASA Astrophysics Data System (ADS)

Hsing, Lai

2004-03-01

Microstrip ring resonators with quality factor (Q) over 10^4 at temperature 5 K were fabricated using the double-side YBa_2Cu_3O_7-δ (YBCO) films deposited on LaAlO3 (LAO) substrates. By placing a narrow gap in the ring resonator, the original fundamental resonating mode (3.61 GHz) splits into two modes (1.80 GHz and 5.33 GHz) with distinct resonating frequencies. The samples allow us to determine the temperature and the frequency dependences of penetration depth and microwave conductivity for various underdoped-cuprates by using Drude formula and the modified two-fluid model. The natures of the order parameter of high-Tc superconductivity in the underdoped cases are shown to be of d-wave type in an exact manner. In particular, the Fermi-liquid correction factor α ^2 and the vertex correction factor β from the model, proposed by Wen and Lee, can be estimated that α ^2 is doping independent in the underdoped regime and β decreases as oxygen content is decreasing in our experiment data. All these results are independent of frequencies as well. The results reveal that the interaction between quasiparticles is insensitive dependence of the impurity concentrations due to oxygen deficiency on the CuO chain and the impurity potential for forward scattering approaches the same as back scattering with more oxygen deficiency.

Phase compatibilities of YBa2Cu3O(9-delta) type structure in quintenary systems Y-Ba-Cu-O-X (impurity)

NASA Technical Reports Server (NTRS)

Karen, P.; Fjellvag, H.; Kjekshus, A.

1990-01-01

Electrical transport properties of the oxidic high T(sub c) superconductors are significantly affected by the presence of minor amounts of various elements adventing as impurities, e.g., from the chemical environment during manufacturing. YBa2Cu3O(9-delta) is prone to an extinction of the superconductivity on (partial) substitution of all four elemental components. E.g., Pr (for Y), La (for Ba), Zn (for Cu) or peroxygroup (for O) substituents will alter some of the superconductivity preconditions, like mixed valence state in Cu3O7/O(9-delta) network or structural distortion of the network. Although various pseudoternary chemical equilibrium phase diagrams of the Y(O)-Ba(O)-Cu(O) system now are available, no consensus is generally shown, however, this is partly due to lack of compatible definitions of the equilibrium conditions. Less information is available about the phase compatibilities in the appropriate quaternary phase diagram (including oxygen) and virtually no information exists about any pentenary phase diagrams (including one impurity). Unfortunately, complexity of such systems, stemming both from number of quaternary or pentenary compounds and from visualizing the five-component phase system, limits this presentation to more or less close surroundings of the YBa2Cu3O(9-delta) type phase in appropriate pseudoquaternary or pseudopseudoternary diagrams, involving Y-Ba-Cu and O, O-CO2, alkaline metals, Mg and alkaline earths, and Sc and most of the 3-d and 4-f elements. The systems were investigated by means of x ray diffraction, neutron diffraction and chemical analytical methods on samples prepared by sol-gel technique from citrates. The superconductivity was characterized by measuring the diamagnetic susceptibility by SQUID.

Theoretical calculation of electron-positron momentum density in YBa 2Cu 3O 7-δ

NASA Astrophysics Data System (ADS)

Massidda, S.

1990-07-01

We present calculations of the electron-positron momentum density for the high- Tc superconductor YBa 2Cu 3O 7-δ for δ=0 and for the insulating parent compound YBa 2Cu 3O 6, based on first-principle electronic structure calculations performed within the local density approximation (LDA) using the full potential linearized augmented plane wave (FLAPW) method. Our results indicate a small overlap of the positron wave function with the CuO 2 plane electrons and, as a consequence, relatively small signals due to the related Fermi surfaces. By contrast, the present calculations show, after the folding of Umklapp terms according to Lock, Crisp and West, clear Fermi surface breaks arising from the Cu-O chain bands. No general agreement with existing experiments allows a clear definition of Fermi surface structures in the latter. A comparison of the calculated momentum with the experimental two-dimensional angular correlation of annihilation radiation (2D-ACAR) recently measured in Geneva shows an overall agreement for the insulating compound, despite the spurious LDA metallic state, and possibly suggests the importance of O vacancies in experiments performed on non-stoichiometric YBa 2Cu 3O 7-δ samples.

XANES and EXAFS study of Au-substituted YBa2Cu3O(7-delta)

NASA Technical Reports Server (NTRS)

Ruckman, Mark W.; Hepp, Aloysius F.

1990-01-01

The near-edge structure (XANES) of the Au L3 and Cu K edges of YBa2Au(0.3)Cu(2.7)O(7-delta) was studied. X ray diffraction suggests that Au goes on the Cu(1) site and XANES shows that this has little effect on the oxidation state of the remaining copper. The gold L3 edge develops a white line feature whose position lies between that of trivalent gold oxide (Au2O3) and monovalent potassium gold cyanide (KAu(CN)2) and whose intensity relative to the edge step is smaller than in the two reference compounds. The L3 EXAFS for Au in the superconductor resembles that of Au2O3. However, differences in the envelope of the Fourier filtered component for the first shell suggest that the local structure of the Au in the superconductor is not equivalent to Au2O3.

Method for making high-critical-current-density YBa.sub.2 Cu.sub.3 O.sub.7 superconducting layers on metallic substrates

DOEpatents

Feenstra, Roeland; Christen, David; Paranthaman, Mariappan

1999-01-01

A method is disclosed for fabricating YBa.sub.2 Cu.sub.3 O.sub.7 superconductor layers with the capability of carrying large superconducting currents on a metallic tape (substrate) supplied with a biaxially textured oxide buffer layer. The method represents a simplification of previously established techniques and provides processing requirements compatible with scale-up to long wire (tape) lengths and high processing speeds. This simplification has been realized by employing the BaF.sub.2 method to grow a YBa.sub.2 Cu.sub.3 O.sub.7 film on a metallic substrate having a biaxially textured oxide buffer layer.

Investigations of YBa2Cu3O y films sputtered onto a substrate of amorphous quartz with a platinum buffer layer

NASA Astrophysics Data System (ADS)

Blinova, Yu. V.; Snigirev, O. V.; Porokhov, N. V.; Evlashin, S. A.

2017-10-01

Results of investigations using X-ray diffraction and scanning electron microscopy of composite materials made from YBa2Cu3O y films sputtered (using various regimes) onto a substrate of amorphous quartz with a platinum buffer layer, have been given.

Ultrafast relaxation dynamics in BiFeO 3/YBa 2Cu 3O 7 bilayers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Springer, D.; Nair, Saritha K.; He, Mi

The temperature dependence of the relaxation dynamics in the bilayer thin film heterostructure composed of multiferroic BiFeO 3 (BFO) and superconducting YBa 2Cu 3O 7 (YBCO) grown on (001) SrTiO 3 substrate is studied by time-resolved pump-probe technique, and compared with that of pure YBCO thin film grown under the same growth conditions. The superconductivity of YBCO is found to be retained in the heterostructure. We observe a speeding up of the YBCO recombination dynamics in the superconducting state of the heterostructure, and attribute it to the presence of weak ferromagnetism at the BFO/YBCOinterface as observed inmagnetization data. An extensionmore » of the Rothwarf-Taylor model is used to fit the ultrafast dynamics of BFO/YBCO, that models an increased quasiparticle occupation of the ferromagnetic interfacial layer in the superconducting state of YBCO.« less

Ultrafast relaxation dynamics in BiFeO 3/YBa 2Cu 3O 7 bilayers

DOE PAGES

Springer, D.; Nair, Saritha K.; He, Mi; ...

2016-02-12

The temperature dependence of the relaxation dynamics in the bilayer thin film heterostructure composed of multiferroic BiFeO 3 (BFO) and superconducting YBa 2Cu 3O 7 (YBCO) grown on (001) SrTiO 3 substrate is studied by time-resolved pump-probe technique, and compared with that of pure YBCO thin film grown under the same growth conditions. The superconductivity of YBCO is found to be retained in the heterostructure. We observe a speeding up of the YBCO recombination dynamics in the superconducting state of the heterostructure, and attribute it to the presence of weak ferromagnetism at the BFO/YBCOinterface as observed inmagnetization data. An extensionmore » of the Rothwarf-Taylor model is used to fit the ultrafast dynamics of BFO/YBCO, that models an increased quasiparticle occupation of the ferromagnetic interfacial layer in the superconducting state of YBCO.« less

Dependence of millimeter wave surface resistance on the deposition parameters of laser ablated YBa2Cu3O(x) thin films

NASA Technical Reports Server (NTRS)

Wosik, J.; Robin, T.; Davis, M.; Wolfe, J. C.; Forster, K.; Deshmukh, S.; Bensaoula, A.; Sega, R.; Economou, D.; Ignatiev, A.

1990-01-01

Measurements of millimeter-wave surface resistance versus temperature have been performed for YBa2Cu3O(x) thin films on 100 line-type SrTiO(3) substrates using a TE(011) cylindrical copper cavity at 80 GHz. The 0.6-micron thick films were grown at several deposition temperatures in the range 690 C to 810 C by means of a pulsed excimer laser ablation technique. A surface resistance minimum (60 milliohm at 77 K) near 770 C is shown to correlate with a minimum in c-axis lattice parameter (11.72 A). The highest value of Tc also occurs near this temperature. The surface resistance of films deposited at 790 C on 110 line-type LaAlO3 subtrates is lower, reaching 8 milliohm at 98 GHz and 80 K, demonstrating the influence of substate material on film quality.

Physical properties of YBa 2Cu 3O 7- δ thin films using microstrip ring resonators technique

NASA Astrophysics Data System (ADS)

Lai, L. S.; Zeng, H. K.; Juang, J. Y.; Wu, K. H.; Uen, T. M.; Lin, J. Y.; Gou, Y. S.

2006-09-01

Microstrip ring resonators with quality factor ( Q) over 10 4 at temperature 5 K, were fabricated using the double-side YBa 2Cu 3O 7- δ (YBCO) epitaxial films deposited on LaAlO 3 (LAO) substrates. By placing a narrow gap in the ring resonator, we observed that the original fundamental resonating mode (resonance frequency f = 3.61 GHz) splits into a dual-mode with different resonating frequencies ( f = 1.80 GHz and f = 5.33 GHz). These two kinds of the resonator allow us to determine the temperature and frequency dependences of the magnetic penetration depth λ( T, f) and the surface loss. Several salient features of the above findings related to the nature of low-lying excitations for high- Tc superconductivity as a function of oxygen content will be elucidated. In particular, the current models, suggested by Wen and Lee, will be examined in a quantitative manner. It allows us to give a justification of quasiparticle as Fermi-liquid in the superconducting state. In addition, an equivalent inductance circuit model is suggested to account for the occurrence of the dual-mode resonance.

Synthesis of high-oxidation Y-Ba-Cu-O phases in superoxygenated thin films

NASA Astrophysics Data System (ADS)

Zhang, H.; Gauquelin, N.; McMahon, C.; Hawthorn, D. G.; Botton, G. A.; Wei, J. Y. T.

2018-03-01

It is known that solid-state reaction in high-pressure oxygen can stabilize high-oxidation phases of Y-Ba-Cu-O superconductors in powder form. We extend this superoxygenation concept of synthesis to thin films which, due to their large surface-to-volume ratio, are more reactive thermodynamically. Epitaxial thin films of YBa2Cu3O7 -δ grown by pulsed laser deposition are annealed at up to 700 atm O2 and 900 ∘C , in conjunction with Cu enrichment by solid-state diffusion. The films show the clear formation of Y2Ba4Cu7O15 -δ and Y2Ba4Cu8O16 as well as regions of YBa2Cu5O9 -δ and YBa2Cu6O10 -δ phases, according to scanning transmission electron microscopy, x-ray diffraction, and x-ray absorption spectroscopy. Similarly annealed YBa2Cu3O7 -δ powders show no phase conversion. Our results demonstrate a route of synthesis towards discovering more complex phases of cuprates and other superconducting oxides.

Effectiveness of BaTiO 3 dielectric patches on YBa 2Cu 3O 7 thin films for MEM switches

DOE PAGES

Vargas, J.; Hijazi, Y.; Noel, J.; ...

2014-05-12

A micro-electro-mechanical (MEM) switch built on a superconducting microstrip filter will be utilized to investigate BaTiO 3 dielectric patches for functional switching points of contact. Actuation voltage resulting from the MEM switch provokes static friction between the bridge membrane and BaTiO 3 insulation layer. Furthermore, the dielectric patch crystal structure and roughness affect the ability of repetitively switching cycles and lifetime. We performed a series of experiments using different deposition methods and RF magnetron sputtering was found to be the best deposition process for the BaTiO 3 layer. The effect examination of surface morphology will be presented using characterization techniquesmore » as x-ray diffraction, SEM and AFM for an optimum switching device. The thin film is made of YBa 2Cu 3O 7 deposited on LaAlO 3 substrate by pulsed laser deposition. In our work, the dielectric material sputtering pressure is set at 9.5x10 -6 Torr. The argon gas is released through a mass-flow controller to purge the system prior to deposition. RF power is 85 W at a distance of 9 cm. The behavior of Au membranes built on ultimate BaTiO 3 patches will be shown as part of the results. These novel surface patterns will in turn be used in modelling other RF MEM switch devices such as distributed-satellite communication system operating at cryogenic temperatures.« less

Analysis of low-field isotropic vortex glass containing vortex groups in YBa2Cu3O7−x thin films visualized by scanning SQUID microscopy

PubMed Central

Wells, Frederick S.; Pan, Alexey V.; Wang, X. Renshaw; Fedoseev, Sergey A.; Hilgenkamp, Hans

2015-01-01

The glass-like vortex distribution in pulsed laser deposited YBa2Cu3O7 − x thin films is observed by scanning superconducting quantum interference device microscopy and analysed for ordering after cooling in magnetic fields significantly smaller than the Earth's field. Autocorrelation calculations on this distribution show a weak short-range positional order, while Delaunay triangulation shows a near-complete lack of orientational order. The distribution of these vortices is finally characterised as an isotropic vortex glass. Abnormally closely spaced groups of vortices, which are statistically unlikely to occur, are observed above a threshold magnetic field. The origin of these groups is discussed, but will require further investigation. PMID:25728772

Study of photoirradiation for YBa 2Cu 3O 6+ x compounds and the electron structure by positron experiment

NASA Astrophysics Data System (ADS)

Guosheng, Cheng; Jiaxiang, Shang; Xigui, Li; xianqi, Dai; Xizhong, Wang; Jincang, Zhang

1997-08-01

We present positron lifetime data of YBa 2Cu 3O 6+ x (x=0.92, 0.43) compounds for different photo-irradiation time. It is given that change of the local electron density and vacancy concentration with photoirradiation time. It is found that there is transform at the electronic structure of CuO chains. We also have discussed the effect of photoirradiations time on the electronic structure of YBa 2Cu 3O 6+ x systems and their charge reservoir layer and CuO 2 plane conduction.layer. The positron experimental results support the model of photoinduced oxygen-diffusion mechanism.

Evidence for three-dimensional XY critical properties in underdoped YBa2Cu3O7-δ

NASA Astrophysics Data System (ADS)

Schneider, T.

2007-05-01

We perform a detailed analysis of the reversible magnetization data of Salem-Sugui and Babíc of underdoped and optimally doped YBa2Cu3O7-δ single crystals. Near the zero field transition temperature we observe extended consistency with the properties of the three-dimensional XY universality class, even though the attained critical regime is limited by an inhomogeneity induced finite size effect. Nevertheless, as Tc falls from 93.5to41.5K , the critical amplitude of the in-plane correlation length ξab0 , the anisotropy γ=ξab0/ξc0 and the critical amplitude of the in-plane penetration depth λab0 increase substantially, while the critical amplitude of the c -axis correlation length ξc0 does not change much. As a consequence, the correlation volume Vcorr- increases and the critical amplitude of the specific heat singularity A- decreases dramatically, while the rise of λab0 reflects the behavior of the zero temperature counterpart. Conversely, although ξab0 and λab0 increase with reduced Tc , the ratio λab0/ξab0- , corresponding to the Ginzburg-Landau parameter κab , decreases substantially and YBa2Cu3O7-δ crosses over from an extreme to a weak type-II superconductor.

Trimming the electrical properties on nanoscale YBa2Cu3O7-x constrictions by focus ion beam technique

NASA Astrophysics Data System (ADS)

Lam, Simon K. H.; Bendavid, Avi; Du, Jia

2017-09-01

High temperature superconducting (HTS) nanostructure has a great potential in photon sensing at high frequency due to its fast recovery time. For maximising the coupling efficiency, the normal resistance of the nanostructure needs to be better matched to that of the thin-film antenna, which is typically few tens of ohm. We report on the fabrication of nanoscale high temperature superconducting YBa2Cu3O7-x (YBCO) constrictions using Gallium ion focus ion beam (FIB) technique. The FIB has been used to both remove the YBCO in lateral dimension and also tune its critical current and normal resistance by a combination of surface etching and implantation on the YBCO top layer. High critical current density of 2.5 MA/cm2 at 77 K can be obtained on YBCO nanobridges down to 100 nm in width. Subsequent trimming of the naobridges can lead to a normal resistance value over 50 Ω. Simulation of the Ga ion trajectory has also been performed to compare the measurement results. This method provides a simple step of fabricating nanoscale superconducting detectors such as hot electron bolometer.

Comparative study of electrical transport and magnetic measurements of Y3Ba5Cu8O18±δ and YBa2Cu3O7-δ compounds: intragranular and intergranular superconducting properties

NASA Astrophysics Data System (ADS)

Slimani, Y.; Hannachi, E.; Ben Salem, M. K.; Ben Azzouz, F.; Ben Salem, M.

2018-02-01

We compare the superconducting properties and flux pinning characteristics between YBa2Cu3O7-δ (called Y-123) and Y3Ba5Cu8O18±δ (called Y-358) compounds. Both samples were synthesized through the solid-state reaction. The samples were examined by X-ray diffraction, and scanning electron microscope coupled with energy dispersive spectrometry. The critical current densities of the prepared samples were investigated using current-voltage, magnetization measurements and ac-susceptibility. It is demonstrated that the Y-358 exhibits better superconducting and pinning properties than the Y-123 one. This may be ascribed to the layered structure and the occurrence of a greater number of insulating layers between the CuO2 planes that act as effective pinning sites and consequently conduce to a better fundamental pinning capacity in Y-358.

Effects of process variables on the properties of YBa2Cu3O(7-x) ceramics formed by investment casting

NASA Technical Reports Server (NTRS)

Hooker, M. W.; Taylor, T. D.; Leigh, H. D.; Wise, S. A.; Buckley, J. D.; Vasquez, P.; Buck, G. M.; Hicks, L. P.

1993-01-01

An investment casting process has been developed to produce net-shape, superconducting ceramics. In this work, a factorial experiment was performed to determine the critical process parameters for producing cast YBa2Cu3O7 ceramics with optimum properties. An analysis of variance procedure indicated that the key variables in casting superconductive ceramics are the particle size distribution and sintering temperature. Additionally, the interactions between the sintering temperature and the other process parameters (e.g., particle size distribution and the use of silver dopants) were also found to influence the density, porosity, and critical current density of the fired ceramics.

Dependence of the critical temperature of laser-ablated YBa2Cu3O(7-delta) thin films on LaAlO3 substrate growth technique

NASA Technical Reports Server (NTRS)

Warner, Joseph D.; Bhasin, Kul B.; Miranda, Felix A.

1991-01-01

Samples of LaAlO3 made by flame fusion and Czochralski method were subjected to the same temperature conditions that they have to undergo during the laser ablation deposition of YBa2Cu3O(7 - delta) thin films. After oxygen annealing at 750 C, the LaAlO3 substrate made by two methods experienced surface roughening. The degree of roughening on the substrate made by Czochralski method was three times greater than that on the substrate made by flame fusion. This excessive surface roughening may be the origin of the experimentally observed lowering of the critical temperature of a film deposited by laser ablation on a LaAlO3 substrate made by Czochralski method with respect to its counterpart deposited on LaAlO3 substrates made by flame fusion.

Disorder-controlled superconductivity at YBa2Cu3O7/SrTiO3 interfaces

NASA Astrophysics Data System (ADS)

Garcia-Barriocanal, J.; Perez-Muñoz, A. M.; Sefrioui, Z.; Arias, D.; Varela, M.; Leon, C.; Pennycook, S. J.; Santamaria, J.

2013-06-01

We examine the effect of interface disorder in suppressing superconductivity in coherently grown ultrathin YBa2Cu3O7 (YBCO) layers on SrTiO3 (STO) in YBCO/STO superlattices. The termination plane of the STO is TiO2 and the CuO chains are missing at the interface. Disorder (steps) at the STO interface cause alterations of the stacking sequence of the intracell YBCO atomic layers. Stacking faults give rise to antiphase boundaries which break the continuity of the CuO2 planes and depress superconductivity. We show that superconductivity is directly controlled by interface disorder outlining the importance of pair breaking and localization by disorder in ultrathin layers.

Lower critical field measurements in YBa2Cu3O(6+x) single crystals

NASA Technical Reports Server (NTRS)

Kaiser, D. L.; Swartzendruber, L. J.; Gayle, F. W.; Bennett, L. H.

1991-01-01

The temperature dependence of the lower critical field in YBa2Cu3O(6+x) single crystals was determined by magnetization measurements with the applied field parallel and perpendicular to the c-axis. Results are compared with data from the literature and fitted to Ginzberg-Landau equations by assuming a linear dependence of the parameter kappa on temperature. A value of 7 plus or minus 2 kOe was estimated for the thermodynamic critical field at T = O by comparison of calculated H (sub c2) values with experimental data from the literature.

Nucléation et croissance de films YBa_{2Cu3O_{7 - δ}} déposés par ablation laser sur substrat de MgO(001)

NASA Astrophysics Data System (ADS)

Keller, D.; Gervais, A.; Chambonnet, D.; Belouet, C.; Audry, C.

1995-02-01

In the field of superconducting devices devoted to microwave applications, the crystalline texture of high quality thin films based on YBa{2}Cu{3}O{7 - δ} is of primary importance. This study presents the formation of this texture on MgO substrates with the nucleation and growth steps up to a film thickness of 300 nm as observed by means of AFM, HRTEM and XRD. The influence of deposition temperature on the growth mode is shown and a nucleation/growth model is discussed. The minimum roughness of c_{bot 0}{(^1)} textured films, 300 nm thick and 20 × 20 mm2 in size is as slow as 2 nm. Dans le cadre de la réalisation de composants supraconducteurs de haute qualité à base du composé YBa{2}Cu{3}O{7 - δ} destinés aux applications en hyperfréquences, le contrôle de la texture cristalline des films est de première importance. La formation de celle-ci sur substrat MgO est étudiée depuis la nucléation jusqu'à une épaisseur de 300 nm au moyen de la microscopie à force atomique, de la microscopie électronique en transmission à haute résolution et de la diffraction des rayons X. L'influence de la température de dépôt sur le mode de croissance est abordée et un modèle de nucléation/croissance est discuté. La rugosité minimale des films d'épaisseur 300 nm et de dimensions 20 × 20 mm2 de texture c_{bot 0}{(^1)} est voisine de 2 nm.

Uncovering a new quasi-2D CuO2 plane between the YBa2Cu3O7 and CeO2 buffer layer of coated conductors

NASA Astrophysics Data System (ADS)

Li, Zhi-Xin; Cao, Jin-Jin; Gou, Xiao-Fan; Wang, Tian-Ge; Xue, Feng

2018-01-01

We report a discovery of the quasi-two-dimensional (quasi-2D) CuO2 plane between the superconductor YBa2Cu3O7 (YBCO) and CeO2 buffer layer (mostly used in the fabrication) of coated conductors through the atomistic computer simulations with the molecular dynamics (MD) and first-principle calculations. For an YBCO coated conductor with multilayer structures, the buffer layers deposited onto a substrate are mainly considered to transfer a strong biaxial texture from the substrate to the YBCO layer. To deeply understand the tuning mechanism of the texture transfer, exploring the complete atomic-level picture of the structure between the YBa2Cu3O7/CeO2 interfaces is firstly required. However, the related observation data have not been available due to some big challenges of experimental techniques. With the MD simulations, having tested the accuracy of the potential functions for the YBa2Cu3O7/CeO2 interface, we constructed a total of 54 possible atom stacking models of the interface and identified its most appropriate and stable structure according to the criterion of the interface adhesion energy and the coherent characterization. To further verify the stability of the identified structure, we performed the first-principle calculations to obtain the adhesion energy and developed the general knowledge of the interface structure. Finally, a coherent interface formed with a new built quasi-2D CuO2 plane that is structurally similar to the CuO2 plane inside bulk YBCO was determined.

Controlling BaZrO3 nanostructure orientation in YBa2Cu3O{}_{7-\\delta } films for a three-dimensional pinning landscape

NASA Astrophysics Data System (ADS)

Wu, J. Z.; Shi, J. J.; Baca, F. J.; Emergo, R.; Wilt, J.; Haugan, T. J.

2015-12-01

The orientation phase diagram of self-assembled BaZrO3 (BZO) nanostructures in c-oriented YBa2Cu3O{}7-δ (YBCO) films on flat and vicinal SrTiO3 substrates was studied experimentally with different dopant concentrations and vicinal angles and theoretically using a micromechanical model based on the theory of elasticity. The organized BZO nanostructure configuration was found to be tunable, between c-axis to ab-plane alignment, by the dopant concentration in the YBCO film matrix strained via lattice mismatched substrates. The correlation between the local strain caused by the BZO doping and the global strain on the matrix provides a unique approach for controllable growth of dopant nanostructure landscapes. In particular, a mixed phase of the c-axis-aligned nanorods and the ab-plane-aligned planar nanostructures can be obtained, leading to a three-dimensional pinning landscape with single impurity doping and much improved J c in almost all directions of applied magnetic field.

The effect of temperature cycling typical of low earth orbit satellites on thin films of YBa2Cu3O(7-x)

NASA Technical Reports Server (NTRS)

Mogro-Campero, A.; Turner, L. G.; Bogorad, A.; Herschitz, R.

1990-01-01

The refrigeration of superconductors in space poses a challenging problem. The problem could be less severe if superconducting materials would not have to be cooled when not in use. Thin films of the YBa2Cu3O(7-x) (YBCO) superconductor were subjected to thermal cycling, which was carried out to simulate a large number of eclipses of a low earth orbit satellite. Electrical measurements were performed to find the effect of the temperature cycling. Thin films of YBCO were formed by coevaporation of Y, BaF2, and Cu and postannealing in wet oxygen at 850 C for 3.5 h. The substrates used were (100) SrTiO3, polycrystalline alumina, and oxidized silicon; the last two have an evaporated zirconia layer. Processing and microstructure studies of these types of films have been published. THe zero resistance transition temperatures of the samples used in this study were 91, 82, and 86 K, respectively. The samples were characterized by four point probe electrical measurements as a function of temperature. The parameters measured were: the zero resistance transition temperature, the 10 to 90 percent transition width, and the room temperature resistance, normalized to that measured before temperature cycling. The results for two samples are presented. Each sample had a cumulative exposure. Cycling in atmospheric pressure nitrogen was performed at a rate of about 60 cycles per day, whereas in vacuum the rate was only about 10 cycles per day. The results indicate only little or no changes in the parameters measured. Degradation of superconducting thin films of YBCO has been reported due to storage in nitrogen. It is believed that the relatively good performance of films after temperature cycling is related to the fact that BaF2 was used as an evaporation source. The latest result on extended temperature cycling indicates significant degradation. Further tests of extended cycling will be carried out to provide additional data and to clarify this preliminary finding.

Pulsed laser deposition of thick BaHfO3-doped YBa2Cu307-δ films on highly alloyed textured Ni-W tapes

NASA Astrophysics Data System (ADS)

Sieger, M.; Hänisch, J.; Iida, K.; Gaitzsch, U.; Rodig, C.; Schultz, L.; Holzapfel, B.; Hühne, R.

2014-05-01

YBa2Cu3O7-δ (YBCO) films with a thickness of up to 3 μm containing nano-sized BaHfO3 (BHO) have been grown on Y2O3/Y-stabilized ZrO2/CeO2 buffered Ni-9at% W tapes by pulsed laser deposition (PLD). Structural characterization by means of X-ray diffraction confirmed that the YBCO layer grew epitaxial. A superconducting transition temperature Tc of about 89 K with a transition width of 1 K was determined, decreasing with increasing BHO content. Critical current density in self-field and at 0.3 T increased with increasing dopant level.

Fluctuation-induced conductivity in melt-textured Pr-doped YBa2Cu3O7-δ composite superconductor

NASA Astrophysics Data System (ADS)

Opata, Yuri Aparecido; Monteiro, João Frederico Haas Leandro; Siqueira, Ezequiel Costa; Rodrigues, Pedro Júnior; Jurelo, Alcione Roberto

2018-04-01

In this study, the effects of thermal fluctuations on the electrical conductivity in melt-textured YBa2Cu3O7-δ, Y0.95Pr0.05Ba2Cu3O7-δ and (YBa2Cu3O7-δ)0.95-(PrBa2Cu3O7-δ)0.05 composite superconductor were considered. The composite superconductor samples were prepared through the top seeding method using melt-textured NdBa2Cu3O7-d seeds. The resistivity measurements were performed with a low-frequency, low-current AC technique in order to extract the temperature derivative and analyze the influence of the praseodymium ion on the normal superconductor transition and consequently on the fluctuation regimes. The results show that the resistive transition is a two-step process. In the normal phase, above the critical temperature, Gaussian and critical fluctuation regimes were identified, while below the critical temperature, in the regime near the approach to the zero-resistance state, the fluctuation conductivity diverges as expected in a paracoherent-coherent transition.

Atomic and electronic structures of BaHfO3-doped TFA-MOD-derived YBa2Cu3O7-δ thin films

NASA Astrophysics Data System (ADS)

Molina-Luna, Leopoldo; Duerrschnabel, Michael; Turner, Stuart; Erbe, Manuela; Martinez, Gerardo T.; Van Aert, Sandra; Holzapfel, Bernhard; Van Tendeloo, Gustaaf

2015-11-01

Tailoring the properties of oxide-based nanocomposites is of great importance for a wide range of materials relevant for energy technology. YBa2Cu3O7-δ (YBCO) superconducting thin films containing nanosized BaHfO3 (BHO) particles yield a significant improvement of the magnetic flux pinning properties and a reduced anisotropy of the critical current density. These films were prepared by chemical solution deposition (CSD) on (100) SrTiO3 (STO) substrates yielding critical current densities up to 3.6 MA cm-2 at 77 K and self-field. Transport in-field J c measurements demonstrated a high pinning force maximum of around 6 GN/m3 for a sample annealed at T = 760 °C that has a doping of 12 mol% of BHO. This sample was investigated by scanning transmission electron microscopy (STEM) in combination with electron energy-loss spectroscopy (EELS) yielding strain and spectral maps. Spherical BHO nanoparticles of 15 nm in size were found in the matrix, whereas the particles at the interface were flat. A 2 nm diffusion layer containing Ti was found at the YBCO (BHO)/STO interface. Local lattice deformation mapping at the atomic scale revealed crystal defects induced by the presence of both sorts of BHO nanoparticles, which can act as pinning centers for magnetic flux lines. Two types of local lattice defects were identified and imaged: (i) misfit edge dislocations and (ii) Ba-Cu-Cu-Ba stacking faults (Y-248 intergrowths). The local electronic structure and charge transfer were probed by high energy resolution monochromated electron energy-loss spectroscopy. This technique made it possible to distinguish superconducting from non-superconducting areas in nanocomposite samples with atomic resolution in real space, allowing the identification of local pinning sites on the order of the coherence length of YBCO (˜1.5 nm) and the determination of 0.25 nm dislocation cores.

Crossover between superconductivity and magnetism in SrRuO3 mesocrystal embedded YBa2Cu3O7-x heterostructures.

PubMed

Suresh, Vandrangi; Lin, Jheng-Cyuan; Liu, Heng-Jui; Zhang, Zaoli; Chiang, Ping-Chih; Hsun, Yu-Ching; Chen, Yi-Chun; Lin, Jiunn-Yuan; Chu, Ying-Hao

2016-11-03

The competition between superconductivity and ferromagnetism poses great challenges and has attracted renewed interest for applications in novel spintronic devices. In order to emphasize their interactions, we fabricated a heterostructure composed of superconducting YBa 2 Cu 3 O 7-δ (YBCO) film embedded with itinerant ferromagnetic SrRuO 3 (SRO) mesocrystals. Starting from a doping concentration of 10 vol% of SRO mesocrystal in a YBCO matrix, corresponding to the density of SRO nanocrystals ∼5 × 10 9 cm -2 , which exhibits the typical characteristic of a metal-superconductor transition, and then increasing the magnetic interactions as a function of SRO embedment, the electronic correlation and the interplay between superconductivity and magnetism throughout the temperature regime were investigated. A metal-insulator transition in the normal state of YBCO and a crossover between superconductivity and magnetism at low temperatures were found upon increasing the density of nano-size SRO crystallites in the YBCO matrix as a consequence of competing interactions between these two ordered phases.

Novel configuration of processing bulk textured YB 2Cu 3O 7-x superconductor by seeded infiltration growth method

NASA Astrophysics Data System (ADS)

Cao, Haitao; Moutalbi, Nahed; Harnois, Christelle; Hu, Rui; Li, Jinshan; Zhou, Lian; Noudem, Jacques G.

2010-01-01

Mono-domain YBa 2Cu 3O 7-x (Y123) bulk superconductors have been processed using seeded infiltration growth technique (SIG). The combination of melt infiltrated liquid source (Ba 3Cu 5O 8) into the Y 2BaCuO 5 (Y211) pre-form and the nucleation of Y123 domain from SmBa 2Cu 3O 7 crystal seed has been investigated. The different configurations of SIG process were compared in this study. In addition, the effect of the starting Y211 particles size has been studied. The results reveal that, the Y211 particle size and different configurations strongly influence the properties of the final bulk superconductor sample.

Peak effect in untwinned YBa 2Cu 3O 7-δ single crystals

NASA Astrophysics Data System (ADS)

D'Anna, G.; André, M.-O.; Indenbom, M. V.; Benoit, W.

1994-12-01

We report on the observation of a weak effect of the critical current density in untwinned YBa 2Cu 3O 7-δ single crystals of different purity, using a low frequency torsion pendulum. We construct the peak effect line and the irreversibility line.

Scanning micro-Hall probe mapping of magnetic flux distributions and current densities in YBa{sub 2}Cu{sub 3}O{sub 7}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xing, W.; Heinrich, B.; Zhou, H.

1994-12-31

Mapping of the magnetic flux density B{sub z} (perpendicular to the film plane) for a YBa{sub 2}Cu{sub 3}O{sub 7} thin-film sample was carried out using a scanning micro-Hall probe. The sheet magnetization and sheet current densities were calculated from the B{sub z} distributions. From the known sheet magnetization, the tangential (B{sub x,y}) and normal components of the flux density B were calculated in the vicinity of the film. It was found that the sheet current density was mostly determined by 2B{sub x,y}/d, where d is the film thickness. The evolution of flux penetration as a function of applied field willmore » be shown.« less

Effects of graphene oxide doping on the structural and superconducting properties of YBa2Cu3O7-δ

NASA Astrophysics Data System (ADS)

Dadras, S.; Falahati, S.; Dehghani, S.

2018-05-01

In this research we reported the effects of graphene oxide (GO) doping on the structural and superconducting properties of YBa2Cu3O7-δ (YBCO) high temperature superconductors. We synthesized YBCO powder by sol-gel method. After calcination, the powder mixed with different weight percent (0, 0.1, 0.3, 0.7, 1 wt.%) of GO. Refinement of X-ray diffraction (XRD) was carried out by material analysis using diffraction (MAUD) program to obtain the structural parameters such as lattice parameters, site occupancy of different atoms and orthorhombicity value for the all samples. Results show that GO doping does not change the structure of YBCO compound, Cu (1), Cu (2) and oxygen sites occupancy. It seems that GO remains between the grains and can play the role of weak links. We found that GO addition to YBCO compound increases transition temperature (TC). The oxygen contents of the all GO-doped samples are increased with respect to the pure one. The strain (ɛ) of the samples obtained from Williamson-Hall method, varies with increasing of GO doping. The scanning electron microscopy (SEM) images of the samples show better YBCO grain connections by GO doping.

YBa_2Cu_3O_{7-δ} : in pursuit of the ideal microstructure

NASA Astrophysics Data System (ADS)

Smith, D. S.; Suasmoro, S.; Lejeune, M.; Rabier, J.; Denanot, M. F.; Heintz, J. M.; Magro, C.; Bonnet, J. P.

1992-02-01

This paper examines the role of different factors in the microstructure of ceramic YBa2Cu3O{7-δ} with emphasis on its electrical response. In particular we discuss : 1. the effect of microstructural variations on j_c and ρ_{300}, 2. measurement of j_c, 3. the presence of minor phases and carbonates, 4. oxygen uptake and microcracks, 5. plastic deformation and related structural defects. Dans cet article, nous examinons d'une part la réponse électrique de céramiques supraconductrices massives de type YBa2Cu3O{7-δ} et d'autre part sa relation avec la microstructure. Nous présenterons successivement : 1. L'incidence de modifications microstructurales sur les valeurs de j_c et ρ_{300}, 2. les mesures expérimentales de j_c, 3. la présence de phases minoritaires et de carbonates, 4. la reprise d'oxygène et la microfissuration, 5. la déformation plastique et les défauts structuraux associés.

Correlation between superfluid density and T(C) of underdoped YBa2Cu3O6+x near the superconductor-insulator transition.

PubMed

Zuev, Yuri; Kim, Mun Seog; Lemberger, Thomas R

2005-09-23

We report measurements of the ab-plane superfluid density n(s) (magnetic penetration depth lambda) of heavily underdoped films of YBa2Cu3O6+x, with T(C)'s from 6 to 50 K. We find the characteristic length for vortex unbinding transition equal to the film thickness, suggesting strongly coupled CuO2 layers. At the lowest dopings, T(C) is as much as 5 times larger than the upper limit set by the 2D Kosterlitz-Thouless-Berezinskii transition temperature calculated for individual CuO2 bilayers. Our main finding is that T(C) is not proportional to n(s)(0); instead, we find T(C) proportional to ns(1/2.3+/-0.4). This conflicts with a popular point of view that quasi-2D thermal phase fluctuations determine the transition temperature.

Preparation, Iodometric Analysis, and Classroom Demonstration of Superconductivity in YBa2Cu3O8-x.

ERIC Educational Resources Information Center

Harris, Daniel C.; And Others

1987-01-01

Described is a student preparation of YBa2Cu3O8-x, a classroom demonstration of its superconductivity, and an analytical chemistry experiment dealing with the oxidation state of copper in the material. (RH)

Study on the photo-induced oxygen reordering in YBa2Cu3O6+x

NASA Astrophysics Data System (ADS)

Milić, M. M.; Lazarov, N. Dj.; Cucić, D. A.

2012-05-01

Effect of the long term illumination of the YBa2Cu3O6+x with visible light or ultraviolet irradiation on its superconducting properties was studied in the frame of a simple theoretical model, which assumes that photodoping triggers rearrangement of oxygen monomers in the chain layers thus causing the enhancement of the average chain length, lav. Since, according to the model of charge transfer mechanism, long CuO chains are better electronic hole donors than the short ones, increase of the average chain length induces additional holes transfer from chain layers to the superconducting CuO2 planes which in turn leads to the increase of the superconducting transition temperature Tc. By the use of the expression for the chain length probability distribution and numerically calculated values for the average chain length in the non-excited system, we were able to estimate the doping p (number of holes per one Cu atom in the superconducting CuO2 planes) and Tc enhancement due to photo-induced oxygen reordering. The theoretical results are compared with available experimental data.

The early growth and interface of YBa 2Cu 3O y thin films deposited on YSZ substrates

NASA Astrophysics Data System (ADS)

Gao, J.; Tang, W. H.; Yau, C. Y.

2001-11-01

Epitaxial thin films of YBa 2Cu 3O y (YBCO) have been prepared on yttrium-stabilized zirconia substrates with and without a buffer layer. The early growth, crystallinity and surface morphology of these thin films have been characterized by X-ray diffraction, rocking curves, scanning electron microscope, in situ conductance measurements, and surface step profiler. The full width at half maximum of the ( 0 0 5 ) peak of rocking curve was found to be less than 0.1°. Over a wide scanning range of 2000 μm the average surface roughness is just 5 nm, indicating very smooth films. Grazing incident X-ray reflection and positron annihilation spectroscopy shows well-defined interfaces between layers and substrate. By applying a new Eu 2CuO 4 (ECO) buffer layer the initial formation of YBCO appears to grow layer-by-layer rather than the typical island growth mode. The obtained results reveal significant improvements at the early formation and crystallinity of YBCO by using the 214-T ‧ ECO as a buffer layer.

Defect ordering in YBa 2Cu 3O 6.5 and YBa 2Cu 3O 6.6: Synthesis and characterization by neutron and electron diffraction

NASA Astrophysics Data System (ADS)

Lin, Y. P.; Greedan, J. E.; O'Reilly, A. H.; Reimers, J. N.; Stager, C. V.; Post, M. L.

1990-02-01

Polycrystalline samples of YBa 2Cu 3O 6.5 and YBa 2Cu 3O 6.6 were prepared by oxygen titration of YBa 2 Cu 3O 6.0 at 450°C followed by slow cooling to room temperature. Both samples showed evidence for the a' = 2a supercell in individual grains by electron diffraction as reported previously. In addition the superlattice was observed in neutron powder diffraction indicating that the bulk material is also well ordered. In this study the YBa 2Cu 3O 6.6 phase showed longer correlation lengths for ordering along both a* and b* than YBa 2Cu 3O 6.5. For the former compound the powder-averaged, sample-averaged a* correlation distance is 26A˚from neutron diffraction. Analysis of electron diffraction profiles on selected single crystals give correlation lengths along a*, b*, and c* of 100, 200, and 50A˚, respectively. Dark field imaging discloses the presence of striped, ordered domains elongated along b* with a distribution of sizes. Both neutron diffraction and dark field imaging indicate that the volume fraction of the ordered domains is about 50%. A correlation is noted between the Meissner Effect and the extent of defect ordering in the bulk samples of the two phases.

Investigation of magnetic properties of superconductors Y0.98 - x Cax Co0.02 Ba2 Cu3O7 - δ

NASA Astrophysics Data System (ADS)

Pourasad, Sepideh; Shakeripour, Hamideh; Hosseini, SeyedSajad; Salamati, Hadi

2018-06-01

The effect of Co2+, 3+ and Ca2+ substitution in Y3+ site in YBa2Cu3O7-δ superconductor has been studied. The series of high temperature superconducting samples of Y1-y-xCoyCaxBa2Cu3O7-δ with 0 ≤ x ≤ 0.015 and y = 0.020 were prepared by solid-state reaction method. The samples were characterized for phase purity and lattice parameter variations by X-ray diffraction. The AC susceptibility curves, χ'(T), show that in reserving cobalt fixed sample with the optimum Tc, by substitution of divalent Ca2+ at the trivalent Y3+ site no sensitive increasing happen in the superconducting transition temperature.

Nonthermal response of YBa2Cu3O7-δ thin films to picosecond THz pulses

NASA Astrophysics Data System (ADS)

Probst, P.; Semenov, A.; Ries, M.; Hoehl, A.; Rieger, P.; Scheuring, A.; Judin, V.; Wünsch, S.; Il'in, K.; Smale, N.; Mathis, Y.-L.; Müller, R.; Ulm, G.; Wüstefeld, G.; Hübers, H.-W.; Hänisch, J.; Holzapfel, B.; Siegel, M.; Müller, A.-S.

2012-05-01

The photoresponse of YBa2Cu3O7-δ thin film microbridges with thicknesses between 15 and 50 nm was studied in the optical and terahertz frequency range. The voltage transients in response to short radiation pulses were recorded in real time with a resolution of a few tens of picoseconds. The bridges were excited by either femtosecond pulses at a wavelength of 0.8 μm or broadband (0.1-1.5 THz) picosecond pulses of coherent synchrotron radiation. The transients in response to optical radiation are qualitatively well explained in the framework of the two-temperature model with a fast component in the picosecond range and a bolometric nanosecond component whose decay time depends on the film thickness. The transients in the THz regime showed no bolometric component and had amplitudes up to three orders of magnitude larger than the two-temperature model predicts. Additionally THz field-dependent transients in the absence of DC bias were observed. We attribute the response in the THz regime to a rearrangement of vortices caused by high-frequency currents.

Shaping and reinforcement of melt textured YBa2Cu3O7-δ superconductors

NASA Astrophysics Data System (ADS)

Meslin, S.; Harnois, C.; Chubilleau, C.; Horvath, D.; Grossin, D.; Suddhakar, E. R.; Noudem, J. G.

2006-07-01

From porous Y2BaCuO5 (Y211) with various grain sizes, single domain ceramic composites YBa2Cu3Oy/Y2BaCuO5 have been prepared by combination of the infiltration and top seed growth (ITSG) process. In addition, perforated Y123 has been prepared from Y211 by the ITSG method in order to magnify the specific surface and then increase oxygen diffusion into the core of the material. Magnetic and electrical properties were determined and correlate well with the microstructure of the composites and were compared to the conventional doped or undoped YBa2Cu3Oy (Y123). From magnetic measurements, high critical current densities, Jc, of 86 000 A cm-2 have been measured. Transport Jc values higher than 10 600 A cm-2 are reached at 77 K and 0 T, corresponding to the nominal critical currents of 325 A injected reproducibly through sections less than 3.082 mm2. This confirms the high quality of single domains obtained with a well controlled ITSG process. On the other hand, the perforated samples were reinforced using resin impregnation and the flux mapping has been investigated.

Induced Ferromagnetism at BiFeO 3/YBa 2Cu 3O 7 Interfaces

DOE PAGES

Zhu, Jian-Xin; Wen, Xiao-Dong; Haraldsen, J. T.; ...

2014-06-20

We report that transition metal oxides (TMOs) exhibit many emergent phenomena ranging from high-temperature superconductivity and giant magnetoresistance to magnetism and ferroelectricity. In addition, when TMOs are interfaced with each other, new functionalities can arise, which are absent in individual components. Here, we report results from first-principles calculations on the magnetism at the BiFeO 3/YBa 2Cu 3O 7 interfaces. By comparing the total energy for various magnetic spin configurations inside BiFeO 3, we are able to show that a metallic ferromagnetism is induced near the interface. We further develop an interface exchange-coupling model and place the extracted exchange coupling interactionmore » strengths, from the first-principles calculations, into a resultant generic phase diagram. Our conclusion of interfacial ferromagnetism is confirmed by the presence of a hysteresis loop in field-dependent magnetization data. Lastly, the emergence of interfacial ferromagnetism should have implications to electronic and transport properties.« less

In operando evidence of deoxygenation in ionic liquid gating of YBa2Cu3O7-X

PubMed Central

Perez-Muñoz, Ana M.; Schio, Pedro; Poloni, Roberta; Fernandez-Martinez, Alejandro; Rivera-Calzada, Alberto; Salas-Colera, Eduardo; Kinney, Joseph; Leon, Carlos; Santamaria, Jacobo; Garcia-Barriocanal, Javier; Goldman, Allen M.

2017-01-01

Field-effect experiments on cuprates using ionic liquids have enabled the exploration of their rich phase diagrams [Leng X, et al. (2011) Phys Rev Lett 107(2):027001]. Conventional understanding of the electrostatic doping is in terms of modifications of the charge density to screen the electric field generated at the double layer. However, it has been recently reported that the suppression of the metal to insulator transition induced in VO2 by ionic liquid gating is due to oxygen vacancy formation rather than to electrostatic doping [Jeong J, et al. (2013) Science 339(6126):1402–1405]. These results underscore the debate on the true nature, electrostatic vs. electrochemical, of the doping of cuprates with ionic liquids. Here, we address the doping mechanism of the high-temperature superconductor YBa2Cu3O7-X (YBCO) by simultaneous ionic liquid gating and X-ray absorption experiments. Pronounced spectral changes are observed at the Cu K-edge concomitant with the superconductor-to-insulator transition, evidencing modification of the Cu coordination resulting from the deoxygenation of the CuO chains, as confirmed by first-principles density functional theory (DFT) simulations. Beyond providing evidence of the importance of chemical doping in electric double-layer (EDL) gating experiments with superconducting cuprates, our work shows that interfacing correlated oxides with ionic liquids enables a delicate control of oxygen content, paving the way to novel electrochemical concepts in future oxide electronics. PMID:28028236

In operando evidence of deoxygenation in ionic liquid gating of YBa2Cu3O7-X.

PubMed

Perez-Muñoz, Ana M; Schio, Pedro; Poloni, Roberta; Fernandez-Martinez, Alejandro; Rivera-Calzada, Alberto; Cezar, Julio C; Salas-Colera, Eduardo; Castro, German R; Kinney, Joseph; Leon, Carlos; Santamaria, Jacobo; Garcia-Barriocanal, Javier; Goldman, Allen M

2017-01-10

Field-effect experiments on cuprates using ionic liquids have enabled the exploration of their rich phase diagrams [Leng X, et al. (2011) Phys Rev Lett 107(2):027001]. Conventional understanding of the electrostatic doping is in terms of modifications of the charge density to screen the electric field generated at the double layer. However, it has been recently reported that the suppression of the metal to insulator transition induced in VO 2 by ionic liquid gating is due to oxygen vacancy formation rather than to electrostatic doping [Jeong J, et al. (2013) Science 339(6126):1402-1405]. These results underscore the debate on the true nature, electrostatic vs. electrochemical, of the doping of cuprates with ionic liquids. Here, we address the doping mechanism of the high-temperature superconductor YBa 2 Cu 3 O 7-X (YBCO) by simultaneous ionic liquid gating and X-ray absorption experiments. Pronounced spectral changes are observed at the Cu K-edge concomitant with the superconductor-to-insulator transition, evidencing modification of the Cu coordination resulting from the deoxygenation of the CuO chains, as confirmed by first-principles density functional theory (DFT) simulations. Beyond providing evidence of the importance of chemical doping in electric double-layer (EDL) gating experiments with superconducting cuprates, our work shows that interfacing correlated oxides with ionic liquids enables a delicate control of oxygen content, paving the way to novel electrochemical concepts in future oxide electronics.

Superconductor-to-insulator transition and transport properties of underdoped YBa2Cu3O(y) crystals.

PubMed

Semba, K; Matsuda, A

2001-01-15

The carrier-concentration-driven superconductor-to-insulator (SI) transition as well as transport properties in underdoped YBa2Cu3O(y) twinned crystals is studied. The SI transition takes place at y approximately 6.3, carrier concentration n(SI)H approximately 3x10(20) cm(-3), anisotropy rho(c)/rho(ab) approximately 10(3), and the threshold resistivity rho(SI)ab approximately 0.8 mOmega cm which corresponds to a critical sheet resistance h/4e2 approximately 6.5 kOmega per CuO2 bilayer. The evolution of a carrier, nH infiniti y - 6.2, is clearly observed in the underdoped region. The resistivity and Hall coefficient abruptly acquire strong temperature dependence at y approximately 6.5 indicating a radical change in the electronic state.

Comparison of the Microstructure and Flux Pinning Properties of Polycrystalline YBa2Cu3O7-d Containing Zn0.95Mn0.05O or Al2O3 Nanoparticles

NASA Astrophysics Data System (ADS)

Al-Mohsin, R. A.; Al-Otaibi, A. L.; Almessiere, M. A.; Al-badairy, H.; Slimani, Y.; Ben Azzouz, F.

2018-07-01

Here we compare the microstructure and flux pinning properties of polycrystalline YBa2Cu3O7-d (Y-123 or YBCO) containing either Al2O3 or Zn0.95Mn0.05O nanoparticles. Samples were prepared using a standard solid-state reaction process, and nanoparticles were added up to a concentration of 0.1 wt%. The crystal structure, microstructure, electrical and magnetic properties were analyzed using X-ray diffraction, scanning electron microscopy and transmission electron microscopy (TEM), and electrical resistivity and DC magnetization measurements, respectively. TEM observations showed that the addition of Zn0.95Mn0.05O resulted in a high density of fine twins and a variety of interacting microstructures, while Al2O3 addition resulted in a high density of Al-rich nanoscale inhomogeneities embedded in the Y-123 matrix. Flux pinning forces were determined, and predominant pinning mechanisms in the prepared samples were proposed. We evaluated the superconducting properties of YBCO considering the effects of adding insulating or magnetic nanoparticles.

Comparison of the Microstructure and Flux Pinning Properties of Polycrystalline YBa2Cu3O7-d Containing Zn0.95Mn0.05O or Al2O3 Nanoparticles

NASA Astrophysics Data System (ADS)

Al-Mohsin, R. A.; Al-Otaibi, A. L.; Almessiere, M. A.; Al-badairy, H.; Slimani, Y.; Ben Azzouz, F.

2018-03-01

Here we compare the microstructure and flux pinning properties of polycrystalline YBa2Cu3O7-d (Y-123 or YBCO) containing either Al2O3 or Zn0.95Mn0.05O nanoparticles. Samples were prepared using a standard solid-state reaction process, and nanoparticles were added up to a concentration of 0.1 wt%. The crystal structure, microstructure, electrical and magnetic properties were analyzed using X-ray diffraction, scanning electron microscopy and transmission electron microscopy (TEM), and electrical resistivity and DC magnetization measurements, respectively. TEM observations showed that the addition of Zn0.95Mn0.05O resulted in a high density of fine twins and a variety of interacting microstructures, while Al2O3 addition resulted in a high density of Al-rich nanoscale inhomogeneities embedded in the Y-123 matrix. Flux pinning forces were determined, and predominant pinning mechanisms in the prepared samples were proposed. We evaluated the superconducting properties of YBCO considering the effects of adding insulating or magnetic nanoparticles.

Boson localization and universality in YBa2Cu(3-x)M(x)O(7-delta)

NASA Technical Reports Server (NTRS)

Kallio, A.; Apaja, V.; Poykko, S.

1995-01-01

We consider a two component mixture of charged fermions on neutralizing background with all sign combinations and arbitrarily small mass ratios. In the two impurity limit for the heavier component we show that the pair forms a bound state for all charge combinations. In the lowest order approximation we derive a closed form expression Veff(r) for the binding potential which has short-range repulsion followed by attraction. In the classical limit, when the mass of embedded particles is large m2 much greater than m, we can calculate from Veff(r) also the cohesive energy E and the bond length R of a metallic crystal such as lithium. The lowest order result is R = 3.1 A, E = -0.9 eV, not entirely different from the experimental result for lithium metal. The same interaction for two holes on a parabolic band with m2 greater than m gives the quantum mechanical bound state which one may interpret as a boson or local pair in the case of high-Te and heavy fermion superconductors. We also show that for compounds of the type YBa2Cu(3 - x)M(x)O(7 - delta) one can understand most of the experimental results for the superconducting and normal states with a single temperature dependent boson breaking function f(T) for each impurity content x governing the decay of bosons into pairing fermions. In the normal state f(T) turns out to be a linear, universal function, independent of the impurity content I and the oxygen content delta. We predict with universality a depression in Tc(x) with slight down bending in agreement with experiment. As a natural consequence of the model the bosons become localized slightly above Tc due to the Wigner crystallization, enhanced with lattice local field minima. The holes remain delocalized with a linearly increasing concentration in the normal state, thus explaining the rising Hall density. The boson localization temperature T(sub BL) shows up as a minimum in the Hall density R(sub ab)(exp -1). We also give explanation for very recently observed

Boson localization and universality in YBa2Cu(3-x)M(x)O(7-delta)

NASA Astrophysics Data System (ADS)

Kallio, A.; Apaja, V.; Poykko, S.

1995-04-01

We consider a two component mixture of charged fermions on neutralizing background with all sign combinations and arbitrarily small mass ratios. In the two impurity limit for the heavier component we show that the pair forms a bound state for all charge combinations. In the lowest order approximation we derive a closed form expression Veff(r) for the binding potential which has short-range repulsion followed by attraction. In the classical limit, when the mass of embedded particles is large m2 much greater than m, we can calculate from Veff(r) also the cohesive energy E and the bond length R of a metallic crystal such as lithium. The lowest order result is R = 3.1 A, E = -0.9 eV, not entirely different from the experimental result for lithium metal. The same interaction for two holes on a parabolic band with m2 greater than m gives the quantum mechanical bound state which one may interpret as a boson or local pair in the case of high-Te and heavy fermion superconductors. We also show that for compounds of the type YBa2Cu(3 - x)M(x)O(7 - delta) one can understand most of the experimental results for the superconducting and normal states with a single temperature dependent boson breaking function f(T) for each impurity content x governing the decay of bosons into pairing fermions. In the normal state f(T) turns out to be a linear, universal function, independent of the impurity content I and the oxygen content delta. We predict with universality a depression in Tc(x) with slight down bending in agreement with experiment. As a natural consequence of the model the bosons become localized slightly above Tc due to the Wigner crystallization, enhanced with lattice local field minima. The holes remain delocalized with a linearly increasing concentration in the normal state, thus explaining the rising Hall density. The boson localization temperature T(sub BL) shows up as a minimum in the Hall density R(sub ab)(exp -1). We also give explanation for very recently observed

Millimeter wave transmission studies of YBa2Cu3O7-delta thin films in the 26.5 to 40.0 GHz frequency range

NASA Technical Reports Server (NTRS)

Miranda, F. A.; Gordon, W. L.; Bhasin, K. B.; Heinen, V. O.; Warner, J. D.; Valco, G. J.

1989-01-01

Millimeter wave transmission measurements through YBa2Cu3O(7-delta) thin films on MgO, ZrO2 and LaAlO3 substrates, are reported. The films (approx. 1 micron) were deposited by sequential evaporation and laser ablation techniques. Transition temperatures T sub c, ranging from 89.7 K for the Laser Ablated film on LaAlO3 to approximately 72 K for the sequentially evaporated film on MgO, were obtained. The values of the real and imaginary parts of the complex conductivity, sigma 1 and sigma 2, are obtained from the transmission data, assuming a two fluid model. The BCS approach is used to calculate values for an effective energy gap from the obtained values of sigma sub 1. A range of gap values from 2 DELTA o/K sub B T sub c = 4.19 to 4.35 was obtained. The magnetic penetration depth is evaluated from the deduced values of sigma 2. These results are discussed together with the frequency dependence of the normalized transmission amplitude, P/P sub c, below and above T sub c.

Levitation of YBa2Cu3O(7-x) superconductor in a variable magnetic field

NASA Technical Reports Server (NTRS)

Terentiev, Alexander N.; Kuznetsov, Anatoliy A.

1992-01-01

The influence of both a linear alternating and rotational magnetic field component on the levitation behavior of a YBa2Cu3O(7-x) superconductor was examined. The transition from a plastic regime of levitation to an elastic one, induced by an alternating field component, was observed. An elastic regime in contrast to a plastic one is characterized by the unique position of stable levitation and field frequency dependence of relaxation time to this position. It was concluded that the vibrations of a magnet levitated above the superconductor can induce a transition from a plastic regime of levitation to an elastic one. It was found that a rotational magnetic field component induced rotations of a levitated superconductor. Rotational frictional motion of flux lines is likely to be an origin of torque developed. A prototype of a motor based on a levitated superconductor rotor is proposed.

Composition dependence of the in-plane Cu-O bond-stretching LO phonon mode in YBa2Cu3O6+x

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stercil, F.; Egami, T.; Mook Jr, Herbert A

An inelastic pulsed neutron scattering study was performed on the dependence of the dispersion and spectral intensity of the in-plane Cu-O bond-stretching LO phonon mode on doped charge density. The measurements were made in the time-of-flight mode with the multiangle position sensitive spectrometer of the ISIS facility on single crystals of YBa{sub 2}Cu{sub 3}O{sub 6+x} (x=0.15, 0.35, 0.6, 0.7, and 0.95). The focus of the study is the in-plane Cu-O bond-stretching LO phonon mode, which is known for strong electron-phonon coupling and unusual dependence on composition and temperature. It is shown that the dispersions for the samples with x=0.35, 0.6,more » and 0.7 are similar to the superposition of those for x=0.15 and 0.95 samples, and cannot be explained in terms of the structural anisotropy. It is suggested that the results are consistent with the model of nanoscale electronic phase separation, with the fraction of the phases being dependent on the doped charge density.« less

Direct, experimental evidence of the Fermi surface in YBa2Cu3O(7-x)

NASA Astrophysics Data System (ADS)

Haghighi, H.; Kaiser, J. H.; Rayner, S. L.; West, R. N.; Liu, J. Z.; Shelton, R.; Howell, R. H.; Sterne, P. A.; Solal, F. R.; Fluss, M. J.

1991-04-01

We report new measurements of the electron positron momentum spectra of YBa2Cu3O(7-x) performed with ultra-high statistical precision. These data differ from previous results in two significant respects: They show the D(sub 2) symmetry appropriate for untwinned crystals and, more importantly, they show unmistakable, statistically significant, discontinuities that are evidence of a major Fermi surface section. These results provide a partial answer to a question of special significance to the study of high temperature superconductors i.e., the distribution of the electrons in the material, the electronic structure. Special consideration has been given both experimentally and theoretically to the existence and shape of a Fermi surface in the materials and to the superconducting gap. There are only three experimental techniques that can provide details of the electronic structure at useful resolutions. They are angular correlation of positron annihilation radiation, ACAR, angle resolved photo emission, PE, and de Haas van Alphen measurements.

Method of producing superconducting fibers of YBA2CU30X

DOEpatents

Schwartzkopf, Louis A.; Ostenson, Jerome E.; Finnemore, Douglas K.

1990-11-13

Fibers of YBa.sub.2 Cu.sub.3 O.sub.x have been produce by pendant drop melt extraction. This technique involves the end of a rod of YBa.sub.2 Cu.sub.3 O.sub.x melted with a hydrogen-oxygen torch, followed by lowering onto the edge of a spinning wheel. The fibers are up to 10 cm in length with the usual lateral dimensions, ranging from 20 .mu.m to 125 .mu.m. The fibers require a heat treatment to make them superconducting.

Elliptical flux vortices in YBa2Cu3O7

NASA Technical Reports Server (NTRS)

Hickman, H.; Dekker, A. J.; Chen, T. M.

1991-01-01

The most energetically favorable vortex in YBa2Cu3O7 forms perpendicular to an anisotropic plane. This vortex is elliptical in shape and is distinguished by an effective interchange of London penetration depths from one axis of the ellipse to another. By generalizing qualitatively from the isotropic to the anisotropic case, we suggest that the flux flow resistivity for the vortex that forms perpendicular to an anistropic plane should have a preferred direction. Similar reasoning indicates that the Kosterlitz-Thouless transition temperature for a vortex mediated transition should be lower if the vortex is elliptical in shape.

Modification of structural disorder by hydrostatic pressure in the superconducting cuprate YBa2Cu3O6.73

NASA Astrophysics Data System (ADS)

Huang, H.; Jang, H.; Fujita, M.; Nishizaki, T.; Lin, Y.; Wang, J.; Ying, J.; Smith, J. S.; Kenney-Benson, C.; Shen, G.; Mao, W. L.; Kao, C.-C.; Liu, Y.-J.; Lee, J.-S.

2018-05-01

Compelling efforts to improve the critical temperature (Tc) of superconductors have been made through high-pressure application. Understanding the underlying mechanism behind such improvements is critically important; however, much remains unclear. Here we studied ortho-III YBa2Cu3O6.73 (YBCO) using x-ray scattering under hydrostatic pressure (HP) up to ˜6.0 GPa . We found the reinforced oxygen order of YBCO under HP, revealing an oxygen rearrangement in the Cu-O layer, which evidently shows the charge-transfer phenomenon between the Cu O2 plane and Cu-O layer. Concurrently, we also observed no disorder-pinned charge-density-wave signature in Cu O2 plane under HP. This indicates that the oxygen rearrangement modifies the quenched disorder state in the Cu O2 plane. Using these results, we appropriately explain why pressure condition can achieve higher Tc compared with the optimal Tc under ambient pressure in YBa2Cu3O6 +x . As an implication of these results, finally we have discussed that the change in disorder could make it easier for YBa2Cu3O6 +x to undergo a transition to the nematic order under an external magnetic field.

Single domain YBa2Cu3Oy thick films on metallic substrates

NASA Astrophysics Data System (ADS)

Reddy, E. S.; Noudem, J. G.; Goodilin, E. A.; Tarka, M.; Schmitz, G. J.

2003-03-01

The fabrication of single domain YBa2Cu3Oy (123) thick films (10-100 mum) on metallic substrates is reported. The process involves the formation of the 123 phase by a peritectic reaction between an air-brushed dense Y2BaCuO5 (211) layer on a Ag12Pd substrate and infiltrated liquid phases containing barium cuprates and copper oxides. Single domain growth is achieved by seeding the green films with a c-axis oriented NdBa2Cu3Oy crystal prior to processing. The maximum processing temperatures are lowered to 970 °C by modifying the characteristics of the liquid phases meant for infiltration by addition of Ag powder. The fabrication technique, processing conditions for single domain growth and the resulting microstructures are discussed.

Properties of large area ErBa2Cu3O(7-x) thin films deposited by ionized cluster beams

NASA Technical Reports Server (NTRS)

Levenson, L. L.; Stan, Mark A.; Bhasin, Kul B.

1991-01-01

ErBa2Cu3O(7-x) films have been produced by simultaneous deposition of Er, Ba, and Cu from three ionized cluster beam (ICB) sources at acceleration voltages of 0.3 to 0.5 kV. Combining ozone oxidation with ICB deposition at 650 C eliminated any need of post annealing processing. The substrates were rotated at 10 rotations per minute during the deposition which took place at a rate of about 3 to 4 nm. Films with areas up to 70 mm in diameter have been made by ICB deposition. These films, 100 nm thick, were deposited on SrTiO3 (100) substrates at 650 C in a mixture of six percent O3 in O2 at a total pressure of 4 x 10(exp -4) Torr. They had T(sub c) ranging from 84.3 K to 86.8 K over a 70 mm diameter and J(sub c) above 10(exp 6) A/sq cm at 77 K. X ray diffraction measurements of the three samples showed preferential c-axis orientation normal to the substrate surface. Scanning electron micrographs (SEM) of the three samples also show some texture dependence on sample position. For the three samples, there is a correlation between SEM texture, full width at half-maximum of rocking curves and J(sub c) versus temperature curves.

The Formation, Transport Properties and Microstructure of 45 Degrees (001) Tilt Grain Boundaries in Yttrium BARIUM(2) COPPER(3) OXYGEN(7-X) Thin Films

NASA Astrophysics Data System (ADS)

Vuchic, Boris Vukan

1995-01-01

Most high angle grain boundaries in high-T _{c} superconductors exhibit weak link behavior. The Josephson-like properties of these grain boundaries can be used for many device applications such as superconducting quantum interference devices (SQUIDs). The structure-property relationship of different types of 45 ^circ (001) YBa_2 Cu_3O_{7-x} thin film grain boundary junctions are examined to study their weak link nature. A technique, termed sputter-induced epitaxy, is developed to form 45^circ (001) tilt grain boundaries in YBa_2Cu _3O_{7-x} thin films on (100) MgO substrates. A low voltage ion bombardment pre-growth substrate treatment is used to modify the epitaxial orientation relationship between the thin film and the substrate in selected regions. By modifying the orientation of the thin film, grain boundary junctions can be placed in any configuration on the substrate. A variety of pre-growth sputtering conditions in conjunction with atomic force microscopy and Rutherford backscatter spectrometry are used to determine the role of the ions in modifying the substrate surface. Sputter-induced epitaxy is extended to a multilayer MgO/LaAlO_3 substrate, allowing integration of the sputter -induced epitaxy junctions into multilayer structures. The low temperature transport properties of the sputter-induced epitaxy junctions and a set of bi-epitaxial grain boundaries are studied. Individual grain boundaries are isolated and characterized for resistance vs. temperature, current vs. voltage as a function of temperature and magnetic field behavior. Resistive and superconducting grain boundaries are compared. Microstructural analysis is performed using scanning electron microscopy, transmission electron microscopy and high resolution electron microscopy (HREM). Marked differences are observed in the microstructure of resistive and superconducting grain boundaries. HREM studies suggest the importance of the local atomic scale structure of the grain boundary in transport

Electronic correlations in YBa/sub 2/Cu/sub 3/O/sub 7-//sub delta/ from Auger spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balzarotti, A.; De Crescenzi, M.; Giovannella, C.

1987-12-01

Cu L/sub 3/VV Auger spectra of the superconducting compound YBa/sub 2/Cu/sub 3/O/sub 7-//sub delta/ have been measured above and below the critical temperature T/sub c/ = 90 K and compared with those of CuO. In the superconductor a localized peak whose intensity increases with temperature is found. Such a structure, lacking in copper oxide, is attributed to electronic correlations in the Cu 3d/sup 8/ configuration.

Atomic scale real-space mapping of holes in YBa2Cu3O(6+δ).

PubMed

Gauquelin, N; Hawthorn, D G; Sawatzky, G A; Liang, R X; Bonn, D A; Hardy, W N; Botton, G A

2014-07-15

The high-temperature superconductor YBa2Cu3O(6+δ) consists of two main structural units--a bilayer of CuO2 planes that are central to superconductivity and a CuO(2+δ) chain layer. Although the functional role of the planes and chains has long been established, most probes integrate over both, which makes it difficult to distinguish the contribution of each. Here we use electron energy loss spectroscopy to directly resolve the plane and chain contributions to the electronic structure in YBa2Cu3O6 and YBa2Cu3O7. We directly probe the charge transfer of holes from the chains to the planes as a function of oxygen content, and show that the change in orbital occupation of Cu is large in the chain layer but modest in CuO2 planes, with holes in the planes doped primarily into the O 2p states. These results provide direct insight into the local electronic structure and charge transfers in this important high-temperature superconductor.

Direct observation of vortex structure in a high-{Tc} YBa{sub 2}Cu{sub 3}O{sub 7{minus}y} thin film by Bitter decoration method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sugimoto, Akira; Yamaguchi, Tetsuji; Iguchi, Ienari

1999-12-01

The Bitter decoration technique is one of the most powerful techniques to study the vortex structure of superconductor. The authors report the observation of vortex structure in a high {Tc} YBa{sub 2}Cu{sub 3}O{sub 7{minus}y} (YBCO) thin film by Bitter decoration method. The image of vortex structure was monitored by SEM, AFM and high resolution optical microscope. For magnetic field about 4--6mT, a vortex structure is seen. The vortex image varied with changing magnetic field. As compared with the vortex image of a Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+y} single crystal, the observed image appeared to be more randomly distributed.

Optical characterization of sputtered YBaCo 4O 7+ δ thin films

NASA Astrophysics Data System (ADS)

Montoya, J. F.; Izquierdo, J. L.; Causado, J. D.; Bastidas, A.; Nisperuza, D.; Gómez, A.; Arnache, O.; Osorio, J.; Marín, J.; Paucar, C.; Morán, O.

2011-02-01

Thin films of YBaCo 4O 7+ δ were deposited on r (1012)-oriented Al 2O 3 substrates by dc magnetron sputtering. The as-grown films were characterized after their structural, morphological and optical properties. Special attention is devoted to the analysis of the optical response of these films as reports on optical properties of YBaCo 4O 7+ δ, especially in thin film form, are not frequently reported in the literature. Transmittance/absorbance measurements allow for determining two well defined energy gaps at 3.7 and 2.2 eV. In turn, infrared (IR) measurements show infrared transparency in the wave length range 4000-2500 nm with a sharp absorption edge at wave lengths less than 2500 nm. Complementary Raman spectra measurements on the thin films allowed for identifying bands associated with vibrating modes of CoO 4 and YO 6 in tetrahedral and octahedral oxygen coordination, respectively. Additional bands which seemed to stem from Co ions in octahedral oxygen coordination were also clearly identified.

Magnetic susceptibility of YBa2(Cu/1-x/Fe/x/)3O(y) prepared by various heat treatments

NASA Astrophysics Data System (ADS)

Shibata, Tomohiko; Katsuyama, Shigeru; Yoshimura, Kazuyoshi; Kosuge, Koji

1991-02-01

The magnetic susceptibility of YBa2(Cu/1-x/Fe/x/)3O(y) specimens was measured following a standard heat treatment and a special heat treament stabilizing the orthorhombic phase to higher Fe concentrations. The values of the effective magnetic moment per Fe in the Cu1 site, estimated from the magnetic susceptibility and Mossbauer effect measurements, were 4.4 and 2.2 muB for the standard and specially treated specimens, respectively. The smaller effective magnetic moment in the case of specially treated specimens is attributed to the antiferromagnetic coupling between Fe spins at high temperatures.

Modification of structural disorder by hydrostatic pressure in the superconducting cuprate YBa 2 Cu 3 O 6.73

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, H.; Jang, H.; Fujita, M.

Here, compelling efforts to improve the critical temperature (T c) of superconductors have been made through high-pressure application. Understanding the underlying mechanism behind such improvements is critically important; however, much remains unclear. Here we studied ortho-III YBa 2Cu 3O 6.73 (YBCO) using x-ray scattering under hydrostatic pressure (HP) up to ~6.0GPa. We found the reinforced oxygen order of YBCO under HP, revealing an oxygen rearrangement in the Cu-O layer, which evidently shows the charge-transfer phenomenon between the CuO 2 plane and Cu-O layer. Concurrently, we also observed no disorder-pinned charge-density-wave signature in CuO 2 plane under HP. This indicates thatmore » the oxygen rearrangement modifies the quenched disorder state in the CuO 2 plane. Using these results, we appropriately explain why pressure condition can achieve higher T c compared with the optimal T c under ambient pressure in YBa 2Cu 3O 6+x. As an implication of these results, finally we have discussed that the change in disorder could make it easier for YBa 2Cu 3O 6+x to undergo a transition to the nematic order under an external magnetic field.« less

Modification of structural disorder by hydrostatic pressure in the superconducting cuprate YBa 2 Cu 3 O 6.73

DOE PAGES

Huang, H.; Jang, H.; Fujita, M.; ...

2018-05-09

Here, compelling efforts to improve the critical temperature (T c) of superconductors have been made through high-pressure application. Understanding the underlying mechanism behind such improvements is critically important; however, much remains unclear. Here we studied ortho-III YBa 2Cu 3O 6.73 (YBCO) using x-ray scattering under hydrostatic pressure (HP) up to ~6.0GPa. We found the reinforced oxygen order of YBCO under HP, revealing an oxygen rearrangement in the Cu-O layer, which evidently shows the charge-transfer phenomenon between the CuO 2 plane and Cu-O layer. Concurrently, we also observed no disorder-pinned charge-density-wave signature in CuO 2 plane under HP. This indicates thatmore » the oxygen rearrangement modifies the quenched disorder state in the CuO 2 plane. Using these results, we appropriately explain why pressure condition can achieve higher T c compared with the optimal T c under ambient pressure in YBa 2Cu 3O 6+x. As an implication of these results, finally we have discussed that the change in disorder could make it easier for YBa 2Cu 3O 6+x to undergo a transition to the nematic order under an external magnetic field.« less

Investigation of flux penetration in YBa 2Cu 3O 7-δ filaments

NASA Astrophysics Data System (ADS)

Devos, P.; Buekenhoudt, A.; D'Anna, G.; André, M.-O.; Indenbom, M. V.; Benoit, W.; De Batist, R.; Cornelis, J.

1994-12-01

ac Susceptibility measurements using a low frequency torsion pendulum and an ac susceptometer were conducted on YBa 2Cu 3O 7-δ filaments in low magnetic dc fields (≤1T). Different dissipation peaks are observed, dependent on the temperature and the applied amplitude. The peak at low temperatures, which is of intergranular nature is studied in detail. The penetration follows the Bean model and the intergranular creep is observed.

Determination of surface resistance and magnetic penetration depth of superconducting YBa2Cu3O(7-delta) thin films by microwave power transmission measurements

NASA Technical Reports Server (NTRS)

Bhasin, K. B.; Warner, J. D.; Miranda, F. A.; Gordon, W. L.; Newman, H. S.

1991-01-01

A novel waveguide power transmission measurement technique was developed to extract the complex conductivity of superconducting thin films at microwave frequencies. The microwave conductivity was taken of two laser ablated YBa2Cu3O(7-delta) thin films on LaAlO3 with transition temperatures of approximately 86.3 and 82 K, respectively, in the temperature range 25 to 300 K. From the conductivity values, the penetration depth was found to be approximately 0.54 and 0.43 micron, and the surface resistance (R sub s) to be approximately 24 and 36 micro-Ohms at 36 GHz and 76 K for the two films under consideration. The R sub s values were compared with those obtained from the change in the Q-factor of a 36 GHz Te sub 011-mode (OFHC) copper cavity by replacing one of its end walls with the superconducting sample. This technique allows noninvasive characterization of high transition superconducting thin films at microwave frequencies.

Determination of surface resistance and magnetic penetration depth of superconducting YBa2Cu3O(7-delta) thin films by microwave power transmission measurements

NASA Technical Reports Server (NTRS)

Bhasin, K. B.; Warner, J. D.; Miranda, F. A.; Gordon, W. L.; Newman, H. S.

1990-01-01

A novel waveguide power transmission measurement technique was developed to extract the complex conductivity of superconducting thin films at microwave frequencies. The microwave conductivity was taken of two laser ablated YBa2Cu3O(7-delta) thin films on LaAlO3 with transition temperatures of approx. 86.3 and 82 K, respectively, in the temperature range 25 to 300 K. From the conductivity values, the penetration depth was found to be approx. 0.54 and 0.43 micron, and the surface resistance (R sub s) to be approx. 24 and 36 micro-Ohms at 36 GHz and 76 K for the two films under consideration. The R sub s values were compared with those obtained from the change in the Q-factor of a 36 GHz Te sub 011-mode (OFHC) copper cavity by replacing one of its end walls with the superconducting sample. This technique allows noninvasive characterization of high transition temperature superconducting thin films at microwave frequencies.

Evaluation of Characteristic Energy Scales of Pressure Stabilized Oxygen Chain States in YBa2Cu3Ox Films

DTIC Science & Technology

2017-03-14

2], and [4]. In the case of YBa2Cu3O∇x, the application of sufficient uniaxial pressure results in the film having discrete regions of uniform...that discrete regions of uniform oxygen content are stabilized where x ≈ [6, 6.5, 6.72, 6.81, 7]. The latter four oxygen content levels correspond to...associated energy levels of the stabilized lattice states ᝺>, �>, >, and ə>, and find evidence for discrete energy levels of the pressure

Detection and imaging of the oxygen deficiency in single crystalline YBa{sub 2}Cu{sub 3}O{sub 7−δ} thin films using a scanning positron beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reiner, M.; Gigl, T.; Hugenschmidt, C.

2015-03-16

Single crystalline YBa{sub 2}Cu{sub 3}O{sub 7−δ} (YBCO) thin films were grown by pulsed laser deposition in order to probe the oxygen deficiency δ using a mono-energetic positron beam. The sample set covered a large range of δ (0.191 < δ < 0.791) yielding a variation of the critical temperature T{sub c} between 25 and 90 K. We found a linear correlation between the Doppler broadening of the positron electron annihilation line and δ determined by X-ray diffraction. Ab-initio calculations have been performed in order to exclude the presence of Y vacancies and to ensure the negligible influence of potentially present Ba or Cu vacancies tomore » the found correlation. Moreover, scanning with the positron beam allowed us to analyze the spatial variation of δ, which was found to fluctuate with a standard deviation of up to 0.079(5) within a single YBCO film.« less

The microscopic structure of charge density waves in underdoped YBa2Cu3O6.54 revealed by X-ray diffraction

NASA Astrophysics Data System (ADS)

Forgan, E. M.; Blackburn, E.; Holmes, A. T.; Briffa, A. K. R.; Chang, J.; Bouchenoire, L.; Brown, S. D.; Liang, Ruixing; Bonn, D.; Hardy, W. N.; Christensen, N. B.; Zimmermann, M. V.; Hücker, M.; Hayden, S. M.

2015-12-01

Charge density wave (CDW) order appears throughout the underdoped high-temperature cuprate superconductors, but the underlying symmetry breaking and the origin of the CDW remain unclear. We use X-ray diffraction to determine the microscopic structure of the CDWs in an archetypical cuprate YBa2Cu3O6.54 at its superconducting transition temperature ~60 K. We find that the CDWs in this material break the mirror symmetry of the CuO2 bilayers. The ionic displacements in the CDWs have two components, which are perpendicular and parallel to the CuO2 planes, and are out of phase with each other. The planar oxygen atoms have the largest displacements, perpendicular to the CuO2 planes. Our results allow many electronic properties of the underdoped cuprates to be understood. For instance, the CDWs will lead to local variations in the electronic structure, giving an explicit explanation of density-wave states with broken symmetry observed in scanning tunnelling microscopy and soft X-ray measurements.

High-temperature change of the creep rate in YBa2Cu3O7-δ films with different pinning landscapes

NASA Astrophysics Data System (ADS)

Haberkorn, N.; Miura, M.; Baca, J.; Maiorov, B.; Usov, I.; Dowden, P.; Foltyn, S. R.; Holesinger, T. G.; Willis, J. O.; Marken, K. R.; Izumi, T.; Shiohara, Y.; Civale, L.

2012-05-01

Magnetic relaxation measurements in YBa2Cu3O7-δ (YBCO) films at intermediate and high temperatures show that the collective vortex creep based on the elastic motion of the vortex lattice has a crossover to fast creep that significantly reduces the superconducting critical current density (Jc). This crossover occurs at temperatures much lower than the irreversibility field line. We study the influence of different kinds of crystalline defects, such as nanorods, twin boundaries, and nanoparticles, on the high-temperature vortex phase diagram of YBCO films. We found that the magnetization relaxation data is a fundamental tool to understand the pinning at high temperatures. The results indicate that high Jc values are directly associated with small creep rates. Based on the analysis of the depinning temperature in films with columnar defects, our results indicate that the size of the defects is the relevant parameter that determines thermal depinning at high temperatures. Also, the extension of the collective creep regime depends on the density of the pinning centers.

Pinning, thermally activated depinning and their importance for tuning the nanoprecipitate size and density in high J c YBa 2Cu 3O 7-x films

NASA Astrophysics Data System (ADS)

Chen, Zhijun; Kametani, Fumitake; Gurevich, Alex; Larbalestier, David

2009-12-01

YBa 2Cu 3O 7-x (Y123) films with quantitatively controlled artificial nanoprecipitate pinning centers were grown by pulsed laser deposition (PLD) and characterized by transport over wide temperature ( T) and magnetic field ( H) ranges and by transmission electron microscopy (TEM). The critical current density J c was found to be determined by the interplay of strong vortex pinning and thermally activated depinning (TAD), which together produced a non-monotonic dependence of J c on c-axis pin spacing d c. At low T and H, J c increased with decreasing d c, reaching the very high J c ∼ 48 MA/cm 2 ∼20% of the depairing current density J d at 10 K, self-field and d c ∼ 10 nm, but at higher T and H when TAD effects become significant, J c was optimized at larger d c because longer vortex segments confined between nanoprecipitates are less prone to thermal fluctuations. We conclude that precipitates should extend at least several coherence lengths along vortices in order to produce irreversibility fields H irr(77 K) greater than 7 T and maximum bulk pinning forces F p,max(77 K) greater than 7-8 GN/m 3 (values appropriate for H parallel to the c-axis). Our results show that there is no universal pin array that optimizes J c at all T and H.

Large pinning forces and matching effects in YBa2Cu3O7-δ thin films with Ba2Y(Nb/Ta)O6 nano-precipitates

PubMed Central

Opherden, Lars; Sieger, Max; Pahlke, Patrick; Hühne, Ruben; Schultz, Ludwig; Meledin, Alexander; Van Tendeloo, Gustaaf; Nast, Rainer; Holzapfel, Bernhard; Bianchetti, Marco; MacManus-Driscoll, Judith L.; Hänisch, Jens

2016-01-01

The addition of mixed double perovskite Ba2Y(Nb/Ta)O6 (BYNTO) to YBa2Cu3O7−δ (YBCO) thin films leads to a large improvement of the in-field current carrying capability. For low deposition rates, BYNTO grows as well-oriented, densely distributed nanocolumns. We achieved a pinning force density of 25 GN/m3 at 77 K at a matching field of 2.3 T, which is among the highest values reported for YBCO. The anisotropy of the critical current density shows a complex behavior whereby additional maxima are developed at field dependent angles. This is caused by a matching effect of the magnetic fields c-axis component. The exponent N of the current-voltage characteristics (inversely proportional to the creep rate S) allows the depinning mechanism to be determined. It changes from a double-kink excitation below the matching field to pinning-potential-determined creep above it. PMID:26887291

Large pinning forces and matching effects in YBa2Cu3O7-δ thin films with Ba2Y(Nb/Ta)O6 nano-precipitates

NASA Astrophysics Data System (ADS)

Opherden, Lars; Sieger, Max; Pahlke, Patrick; Hühne, Ruben; Schultz, Ludwig; Meledin, Alexander; van Tendeloo, Gustaaf; Nast, Rainer; Holzapfel, Bernhard; Bianchetti, Marco; MacManus-Driscoll, Judith L.; Hänisch, Jens

2016-02-01

The addition of mixed double perovskite Ba2Y(Nb/Ta)O6 (BYNTO) to YBa2Cu3O7-δ (YBCO) thin films leads to a large improvement of the in-field current carrying capability. For low deposition rates, BYNTO grows as well-oriented, densely distributed nanocolumns. We achieved a pinning force density of 25 GN/m3 at 77 K at a matching field of 2.3 T, which is among the highest values reported for YBCO. The anisotropy of the critical current density shows a complex behavior whereby additional maxima are developed at field dependent angles. This is caused by a matching effect of the magnetic fields c-axis component. The exponent N of the current-voltage characteristics (inversely proportional to the creep rate S) allows the depinning mechanism to be determined. It changes from a double-kink excitation below the matching field to pinning-potential-determined creep above it.

Spatial variations in ac susceptibility and microstructure for the YBa2Cu3O(7-x) superconductor and their correlation with room-temperature ultrasonic measurements

NASA Technical Reports Server (NTRS)

Roth, Don J.; Deguire, Mark R.; Dolhert, Leonard E.; Hepp, Aloysius F.

1991-01-01

The spatial (within-sample) uniformity of superconducting behavior and microstructure in YBa2Cu3O(7-x) specimens over the pore fraction range of 0.10 to 0.25 was examined. The viability of using a room-temperature, nondestructive characterization method (ultrasonic velocity imaging) to predict spatial variability was determined. Spatial variations in superconductor properties were observed for specimens containing 0.10 pore fraction. An ultrasonic velocity image constructed from measurements at 1 mm increments across one such specimen revealed microstructural variation between edge and center locations that correlated with variations in alternating-current shielding and loss behavior. Optical quantitative image analysis on sample cross-sections revealed pore fraction to be the varying microstructural feature.

Flux pinning properties of YBa2Cu3O7-δ thin films containing a high density of nanoprecipitates: A comparative study to reveal size effects

NASA Astrophysics Data System (ADS)

Yamasaki, Hirofumi; Yamada, Hiroshi

2017-11-01

Temperature dependence of critical current density Jc(H, T) was measured in moderate magnetic fields (H ⊥ film) in two thermally co-evaporated YBa2Cu3O7-δ (YBCO) thin films (A, B) and two YBCO films (C, D) deposited using a pulsed-laser deposition method. All sample films were grown epitaxially with the c-axis perpendicular to the surface of a single-crystalline substrate. Transmission electron microscopy observation revealed that these four films contained a high density of nanoprecipitates with typical sizes of 3.6 - 5.0 nm (A), 5.0 - 7.1 nm (B), 7.0 - 10.1 nm (C) and 8.7 - 14.3 nm (D). Films A and B contained very fine nanoprecipitates, whose typical diameters Dtyp are smaller than double the estimated Ginzburg-Landau coherence length 2ξab at T = 77 K, and exhibited a steep increase of Jc with decreasing temperature. Whereas, film D, which contained relatively large nanoprecipitates (Dtyp > 2ξab at T ≤ 70 K), exhibited a gradual increase in Jc. This led to a remarkable crossing of the Jc(T) curves. The temperature dependence of Jc(H//c) under a fixed magnetic field is approximated by Jc ∼ (1 - T/Tc)m(1 + T/Tc)2 where the index m is larger for films containing finer precipitates; that is, m(A) > m(B) > m(C) > m(D). This means that finer nanoprecipitates generally cause steeper Jc increase at low temperatures, which is the origin of the observed crossing phenomenon. The experimental results are reasonably explained by several theoretical models based on the direct summation of elementary pinning forces fp calculated by core pinning interactions.

Ultrasonic evaluation of oxidation and reduction effects on the elastic behavior and global microstructure of YBa2Cu3O7-x

NASA Technical Reports Server (NTRS)

Roth, Don J.; Deguire, Mark R.; Dolhert, Leonard E.

1991-01-01

Ultrasonic velocity measurement techniques were used to evaluate the effects of oxidation and reduction on the elastic properties, global microstructure and oxygen content of the YBa2Cu3O(7-x) ceramic superconductor for samples ranging from 70 to 90 pct. of theoretical density. Bulk density, velocity, and elastic modulus generally increased with increasing oxygen content upon oxidation, and this behavior was reversible. Velocity image patterns were similar after oxidation and reduction treatments for a 90 pct. dense sample, although the velocity value at any given point on the sample was changed following the treatments. The unchanging pattern correlated with destructive measurements showing that the spatial pore distribution (fraction and size) was not measurably altered after the treatments. Changes in superconducting behavior, crystal structure, and grain structure were observed consistent with changes in oxygen content.

Redistribution of oxygen ions in single crystal YBa2Cu3O7-x owing to external hydrostatic pressure

NASA Astrophysics Data System (ADS)

Boiko, Yu. I.; Bogdanov, V. V.; Vovk, R. V.; Khadzhai, G. Ya.; Savich, S. V.

2018-01-01

The effect of high hydrostatic pressure on the temperature dependences of the electrical resistance in the basal plane of single crystal YBa2Cu3O7-x with an oxygen deficit is studied. It is found that an external hydrostatic pressure P ≈ 7 kbar substantially intensifies the diffusive coalescence of oxygen clusters, i.e., causes an increase in their average size. This, in turn, produces an increased number of negative U-centers whose presence leads to the appearance of a phase capable of generating paired carriers of electrical charge and is, therefore, characterized by a higher transition temperature Tc. Changes in the form of the temperature and time dependences of the electrical resistivity under external hydrostatic pressure are discussed in terms of this same hypothesis regarding the mechanism of diffusive coalescence of oxygen clusters.

Q factor of megahertz LC circuits based on thin films of YBaCuO high-temperature superconductor

NASA Astrophysics Data System (ADS)

Masterov, D. V.; Pavlov, S. A.; Parafin, A. E.

2008-05-01

High-frequency properties of resonant structures based on thin films of YBa2Cu3O7 δ high-temperature superconductor are studied experimentally in the frequency range 30 100 MHz. The structures planar induction coils with a self-capacitance fabricated on neodymium gallate and lanthanum aluminate substrates. The unloaded Q factor of the circuits exceeds 2 × 105 at 77 K and 40 MHz. Possible loss mechanisms that determine the Q factor of the superconducting resonant structures in the megahertz range are considered.

TOPICAL REVIEW: Review of a chemical approach to YBa2Cu3O7-x-coated superconductors—metalorganic deposition using trifluoroacetates

NASA Astrophysics Data System (ADS)

Araki, Takeshi; Hirabayashi, Izumi

2003-11-01

Large-area, uniform, high critical current density (Jc) YBa2Cu3O7-x (YBCO) superconductor films are now routinely obtained by metalorganic deposition using trifluoroacetates (TFA-MOD). This method does not require any expensive vacuum apparatus at any time during the whole process. Thus, TFA-MOD is regarded as one of the most suitable candidates for fabricating a YBCO tape for many high-power applications. This method originated from an electron beam process using BaF2 developed by Mankiewich et al. Afterwards, Gupta et al reported using TFA-MOD to prepare a similar precursor film. These two ex situ processes used fluorides instead of BaCO3 to avoid the fatal deterioration in Jc, which is caused in the resulting films through metal carboxylic groups. Fluorides not only avoid such deterioration but also lead to perfectly c-axis-oriented epitaxial crystal growth. In conventional metalorganic deposition, nucleation in the precursor film causes random orientation in the resulting film. However, in TFA-MOD, nanocrystallites in the precursor film never cause such disorder. Furthermore, during the firing process of TFA-MOD, water and HF gas diffuse quickly between the film surface and growth front of the YBCO layer. This diffusion never limits the growth rate of YBCO. What distinguishes TFA-MOD from conventional metalorganic deposition? What happens during heat treatment? In this paper, we discuss all the TFA-MOD processes and the peculiar growth scheme of the YBCO layer in TFA-MOD using the model of a quasi-liquid network. In addition, we review the history of TFA-MOD and recent results and discuss the prospects of future applications.

Valence charge fluctuations in YBa/sub 2/Cu/sub 3/O/sub 7-//sub delta/ from core-level spectroscopies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balzarotti, A.; De Crescenzi, M.; Motta, N.

1988-10-01

From x-ray photoemission and Auger measurements of the Cu 2p and O 1s core levels of YBa/sub 2/Cu/sub 3/O/sub 7-//sub delta/ as a function of the oxygen concentration delta, the average copper charge is determined. Evidence is found of dynamic charge fluctuations on the oxygen sublattice giving rise to a greater concentration of trivalent copper at the Cu(1) sites with respect to that determined by the analysis of neutron-diffraction data. On the basis of our experimental results, we introduce a molecular cluster description for the Cu states. The lowest final-states configurations of Cu/sup 2+/ and Cu/sup 3+/ are c3d/sup 10/Lmore » and c3d/sup 10/L/sup 2/, respectively, where c and L denote core holes on copper and oxygen atoms. Oxygen holes have high mobility and a Hubbard correlation energy less than 2 eV, a signature of their delocalization. The effect of temperature on the spectra is minor. Surface degradation modifies the relative intensity of the structures, particularly those of the O spectrum.« less

Macroscopic shape change of melt-processed YBa{sub 2}Cu{sub 3}O{sub x-}Y{sub 2}BaCuO{sub 5} bulk superconductors.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Diko, P.; Goretta, K. C.; Energy Technology

A macroscopic change in the shape of five-domain melt-processed YBa{sub 2}Cu{sub 3}O{sub x}/Y{sub 2}BaCuO{sub 5} bulk superconductors is reported and explained. The change, a distortion from circular cross-section, is attributed to liquid transport from a slower growth front in an a-axis direction to a faster growth front in a c-axis direction at the edge between the a- and c-growth fronts, a phenomenon that we call the edge melt distribution (EMD) effect. Formation of bands of higher Y{sub 2}BaCuO{sub 5} particle density along the a/c growth boundaries, which nearly coincide with {l_brace}110{r_brace}-type planes, is explained by the EMD effect.

Compatibilities of YBa2Cu3O(9-delta) type phase in quintenary systems Y-Ba-Cu-O-X (impurity)

NASA Technical Reports Server (NTRS)

Karen, P.; Braaten, O.; Fjellvag, H.; Kjekshus, A.

1991-01-01

Isothermal phase diagrams at various oxygen pressures were studied by powder diffraction and chemical analytical methods. The components, Y, Ba, Cu, and O (specifically O2, O2-, and O2 sup 2-) are treated, together with C (specifically CO2 and CO2 sup 2-), alkaline metals, Mg, alkaline earths, Sc, 3-d and 4-f elements. Effects of the substitutions at the structural sites of YBa2Cu3O(9-delta) on T sub c are discussed with respect to changes in crystallochemical characteristics of the substituted phase and to the nature of the substituents.

La0.7Sr0.3MnO3: A single, conductive-oxide buffer layer for the development of YBa2Cu3O7-δ coated conductors

NASA Astrophysics Data System (ADS)

Aytug, T.; Paranthaman, M.; Kang, B. W.; Sathyamurthy, S.; Goyal, A.; Christen, D. K.

2001-10-01

Coated conductor applications in power technologies require stabilization of the high-temperature superconducting (HTS) layers against thermal runaway. Conductive La0.7Sr0.3MnO3 (LSMO) has been epitaxially grown on biaxially textured Ni substrates as a single buffer layer. The subsequent epitaxial growth of YBa2Cu3O7-δ (YBCO) coatings by pulsed laser deposition yielded self-field critical current densities (Jc) of 0.5×106A/cm2 at 77 K, and provided good electrical connectivity over the entire structure (HTS+conductive-buffer+metal substrate). Property characterizations of YBCO/LSMO/Ni architecture revealed excellent crystallographic and morphological properties. These results have demonstrated that LSMO, used as a single, conductive buffer layer, may offer potential for use in fully stabilized YBCO coated conductors.

The microscopic structure of charge density waves in underdoped YBa 2Cu 3O 6.54 revealed by x-ray diffraction

DOE PAGES

E. M. Forgan; Huecker, M.; Blackburn, E.; ...

2015-12-09

Charge density wave (CDW) order appears throughout the underdoped high-temperature cuprate superconductors, but the underlying symmetry breaking and the origin of the CDW remain unclear. We use X-ray diffraction to determine the microscopic structure of the CDWs in an archetypical cuprate YBa 2Cu 3O 6.54 at its superconducting transition temperature ~60 K. We find that the CDWs in this material break the mirror symmetry of the CuO 2 bilayers. The ionic displacements in the CDWs have two components, which are perpendicular and parallel to the CuO 2 planes, and are out of phase with each other. The planar oxygen atomsmore » have the largest displacements, perpendicular to the CuO 2 planes. Our results allow many electronic properties of the underdoped cuprates to be understood. For example, the CDWs will lead to local variations in the electronic structure, giving an explicit explanation of density-wave states with broken symmetry observed in scanning tunnelling microscopy and soft X-ray measurements.« less

Interplay between current driven ferromagnetism in charge ordered antiferromagnetic Pr0.5Ca0.5MnO3 and superconducting YBa2Cu3O7-δ thin film multilayer

NASA Astrophysics Data System (ADS)

Baisnab, Dipak Kumar; Sardar, Manas; Amaladass, E. P.; Vaidhyanathan, L. S.; Baskaran, R.

2018-07-01

Thin film multilayer heterostructure of alternate YBa2Cu3O7-δ (YBCO) and Pr0.5Ca0.5MnO3 (PCMO) with thickness of each layer ∼60 nm has been deposited on (100) oriented SrTiO3 substrate by Pulsed Laser Deposition technique. A half portion of the base YBCO layer was masked in situ using mechanical shadow mask and in the remaining half portion, five alternate layers of PCMO and YBCO thin films were deposited. Magnetoresistance measurements were carried out under externally applied magnetic field and injection current. A noticeable damped oscillation of the superconducting transition temperature (TC) of this multilayer with respect to magnetic field is seen. Curiously, the field at which the first minimum in TC occurs, decreases as an injection current is driven perpendicular/parallel to the multilayers. Both these phenomena indicate that ferromagnetic correlation can be induced in antiferromagnetic PCMO thin films by (1) external magnetic field, or (2) injection current. While (1) is well researched, our study indicates that ferromagnetism can be induced by small amount of current in PCMO thin films. This unusual behavior points towards the strongly correlated nature of electrons in PCMO.

Pulsed laser deposition of {CeO_2} and {Ce_{1-x}M_xO_2} (M = La, Zr): Application to insulating barrier in cuprate heterostructures

NASA Astrophysics Data System (ADS)

Berger, S.; Contour, J.-P.; Drouet, M.; Durand, O.; Khodan, A.; Michel, D.; Régi, F.-X.

1998-03-01

SrTiO_3 had been often tentatively used as an insulating barrier for HT superconductor/insulator heterostructures. Unfortunately, the deposition of SrTiO_3 on the YBa_2Cu_3O_7 inverse interface results in a poor epitaxial regrowth producing a high roughness dislocated titanate layer. Taking into account the good matching with YBa_2Cu_3O_7 and LaAlO_3, CeO_2 and Ce_{1-x}M_xO_2 (M = La, Zr), epitaxial layers were grown by pulsed laser deposition on LaAlO_3 substrates and introduced into YBa_2Cu_3O_7 based heterostructures as insulating barrier. After adjusting the growth parameters from RHEED oscillations, epitaxial growth is achieved, the oxide crystal axes being rotated by 45^circ from those of the substrate. The surface roughness of 250 nm thick films is very low with a rms value lower than 0.5 nm over 1;μ m^2. The YBa_2Cu_3O_7 layers of a YBa_2Cu_3O_7/CeO_2 /YBa_2Cu_3O_7 heterostructures grown using these optimized parameters show an independent resistive transition, when the thickness is larger than 25 nm, respectively at T_c_1 = 89.6;K and T_c_2 = 91.4;{K}. SrTiO3 est souvent utilisé comme barrière isolante dans des hétérostructures SIS de cuprates supraconducteurs, cependant les défauts générés lors de la croissance de ce titanate sur l'interface inverse de YBa2Cu3O7 conduisent à un matériau dont la qualité cristalline et les propriétés physiques sont médiocres. L'oxyde de cérium CeO2 est également une barrière isolante potentielle intéressante pour ces structures SIS basées sur YBa2Cu3O7 car cet oxyde cubique (a = 0,5411 nm, asqrt{2}/2 = 0,3825 nm) qui est peu désaccordé par rapport au plan ab du cuprate (Δ a/a = - 0,18 %, Δ b/a = 1,6 %) présente de plus un coefficient de dilatation thermique (10,6 × 10^{-6 circ}C^{-1}) très voisin de celui de YBa2Cu3O7 (13 × 10^{-6 circ}C^{-1}). Nous avons donc étudié l'épitaxie de CeO2 et des oxydes de type Ce{1-x}MxO2 (M = La, Zr) en ablation laser pulsée afin de définir des conditions de

Phonon Dispersion Measurements of YBa 2Cu 3O 6.15 and YBa 2Cu 3O 6.95 by Time-of-Flight Neutron Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chung, J.-H.; Egami, T.; McQueeny, R. J.

We measured the phonon dispersions of YBa{sub 2}Cu{sub 3}O{sub 6.15} and YBa{sub 2}Cu{sub 3}O{sub 6.95} by time-of-flight inelastic neutron scattering. The in-plane bond-stretching modes in the metallic phase showed a distinct a-b plane anisotropy beyond what is expected for structural origin. Such anisotropy in the longitudinal optical modes, which is absent in the TO, suggests strong in-plane anisotropy in the underlying electronic structure. Apical oxygen bond-stretching modes showed a large frequency change between the insulating and the metallic phases. This large softening also is beyond structural origin, and suggests the effect of local electronic environment.

Modification of structural and transport properties in epitaxial YBa2CU3Ox films by pulsed laser irradiation

NASA Astrophysics Data System (ADS)

Chechenin, N. G.; Chernysh, A. V.; Korneev, V. V.; Monakhov, E. V.; Seleznev, B. V.

1993-12-01

Pulsed (~20 ns) laser effects in epitaxial YBa2CU3Ox/SrTiO3 thin films were investigated, using RBS/channeling for compositional and structural characterization and 4-point technique for electrical measurements. It was found that laser pulse melting and following quenching lead to a transition from a single-crystalline to a polycrystalline state in films. The formation of grain boundaries causes a room temperature electrical resistivity increase by a factor 10-40, depending on the initial film properties and on the irradiation conditions. Unlike corpuscular (ions, neutrons) irradiation, the laser pulse induced structural damage did not lead to the disappearance of HTS, which persisted up to the highest laser fluences used. It was found, that a thermal model can consistently describe the fluence dependence of disorder, depth of surface relief and helps, with a simple two-layer model, in understanding of fluence dependence of room temperature resistivity in a relatively thick film. Les effects de pulses laser (~20 ns) sur des films minces épitaxiés d'YBa2Cu3Ox/SrTiO3 ont été étudiés par rétrodiffusion Rutherford et canalisation afin de caractériser leur composition et leur structure et à l'aide de la technique des 4 points pour les mesures électriques. On a trouvé que la fusion par pulse laser suivie par une trempe entraîne une transition d'un film monocristallin vers un film polycristallin. La formation de joints de grains s'accompagne d'une augmentation d'un facteur 10-40, de la résistivité électrique à température ambiante, dépendante des propriétés initiales du film et des conditions d'irradiation. Contrairement à l'irradiation corpusculaire (ions, neutrons) l'endommagement produit par la pulse laser n'entraîne pas la disparition de la superconductivité à haute température (HTS), qui persiste jusqu'aux plus hautes doses utilisées. On a trouvé qu'un modèle thermique peut décrire de façon consistante, la profondeur de la rugosité de

Fabrication of YBa2Cu3O7 twin-boundary-junction dc SQUID by using a focused-ion-beam pattern technique

NASA Astrophysics Data System (ADS)

Lee, Sung Hoon; Lee, Soon-Gul

2017-09-01

We have fabricated YBa2Cu3O7 (YBCO) dc SQUIDs containing nanobridges across twin boundaries of LaAlO3 (LAO) substrates as Josephson elements by using a focused ion beam (FIB) etching method and measured their transport properties. The beam energy was 30 keV and the current was 1.5 pA for the nanobridge pattern. Each bridge with a nominal width of 200 nm crossed a twin boundary in the (100) direction. The SQUID loop had a 10 μm × 10 μm hole with a 5.7 μm average linewidth. The SQUID voltage showed modulations in response to the external flux with a maximum modulation depth of 350 μV at 77.0 K. HR-XRD spectra showed that the epitaxially grown YBCO film was twinned in commensurate with the twinning of the LAO substrate. Tilting of the c-axis of YBCO across the twin boundary is believed to play a role as a tunnel barrier.

Distribution of flux-pinning energies in YBa2Cu3O(7-delta) and Bi2Sr2CaCu2O(8+delta) from flux noise

NASA Astrophysics Data System (ADS)

Ferrari, M. J.; Johnson, Mark; Wellstood, Frederick C.; Clarke, John; Mitzi, D.

1990-01-01

The spectral density of the magnetic flux noise measured in high-temperature superconductors in low magnetic fields scales approximately as the inverse of the frequency and increases with temperature. The temperature and frequency dependence of the noise are used to determine the pinning energies of individual flux vortices in thermal equilibrium. The distribution of pinning energies below 0.1 eV in YBa(2)Cu(3)O(7-delta) and near 0.2 eV in Bi(2)Sr(2)CaCu(2)O(8+delta). The noise power is proportional to the ambient magnetic field, indicating that the vortex motion is uncorrelated.

Comparative study of flux pinning, creep and critical currents between YBaCuO crystals with and without Y2BaCuO5 inclusions

NASA Technical Reports Server (NTRS)

Murakami, Masato; Gotoh, Satoshi; Fujimoto, Hiroyuki; Koshizuka, Naoki; Tanaka, Shoji

1991-01-01

In the Y-Ba-Cu-O system, YBa2Cu3O(x) phase is produced by the following peritectic reaction: Y2BaCuO5 + liquid yields 2YBa2Cu3O(x). Through the control of processing conditions and starting compositions, it becomes possible to fabricate large crystals containing fine Y2BaCuO5(211) inclusions. Such crystals exhibit Jc values exceeding 10000 A/sq cm at 77 K and 1T. Recently, researchers developed a novel process which can control the volume fraction of 211 inclusions. Elimination of 211 inclusions is also possible. In this study, researchers prepared YBaCuO crystals with and without 211 inclusions using the novel process, and compared flux pinning, flux creep and critical currents. Magnetic field dependence of Jc for YBaCuO crystals with and with 211 inclusions is shown. It is clear that fine 211 inclusions can contribute to flux pinning. It was also found that flux creep rate could be reduced by increasing flux pinning force. Critical current density estimates based on the conventional flux pinning theory were in good agreement with experimental results.

YBa2Cu307 superconducting microbolometer linear arrays

NASA Astrophysics Data System (ADS)

Johnson, Burgess R.; Ohnstein, Thomas R.; Marsh, Holly A.; Dunham, Scott B.; Kruse, Paul W.

1992-09-01

Single pixels and linear arrays of microbolometers employing the high-T(subscript c) superconductor YBa(subscript 2)Cu(subscript 3)O(subscript 7) have been fabricated by silicon micromachining techniques. The substrates are 3 in. diameter silicon wafers upon which buffer layers of Si(subscript 3)N(subscript 4) and yttria-stabilized zirconia (YSZ) have been deposited. The YBa(subscript 2)Cu(subscript 3)O(subscript 7) was deposited by ion beam sputtering upon the yttria-stabilized zirconia (YSZ), then photolithographically patterned into serpentines 4 micrometers wide. Anisotropic etching in KOH removed the silicon underlying each pixel, thereby providing the necessary thermal isolation. When operated at 70 degree(s)K with 1 (mu) A dc bias, the D(superscript *) is 7.5 X 10(superscript 8) cm Hz(superscript 1/2)/Watt with a thermal response time of 24 msec.

Thermal conversion of Cu4O3 into CuO and Cu2O and the electrical properties of magnetron sputtered Cu4O3 thin films

NASA Astrophysics Data System (ADS)

Murali, Dhanya S.; Aryasomayajula, Subrahmanyam

2018-03-01

Among the three oxides of copper (CuO, Cu2O, and Cu4O3), Cu4O3 phase (paramelaconite is a natural, and very scarce mineral) is very difficult to synthesize. It contains copper in both + 1 and + 2 valence states, with an average composition Cu2 1+Cu2 2+O3. We have successfully synthesized Cu4O3 phase at room temperature (300 K) by reactive DC magnetron sputtering by controlling the oxygen flow rate (Murali and Subrahmanyam in J Phys D Appl Phys 49:375102, 2016). In the present communication, Cu4O3 thin films are converted to CuO phases by annealing in the air at 680 K and to Cu2O phase when annealed in argon at 720 K; these phase changes are confirmed by temperature-dependent Raman spectroscopy studies. Probably, this is the first report of the conversion of Cu4O3-CuO and Cu2O by thermal annealing. The temperature-dependent (300-200 K) electrical transport properties of Cu4O3 thin films show that the charge transport above 190 K follows Arrhenius-type behavior with activation energy of 0.14 eV. From photo-electron spectroscopy and electrical transport measurements of Cu4O3 thin films, a downward band bending is observed at the surface of the thin film, which shows its p-type semiconducting nature. The successful preparation of phase pure p-type semiconducting Cu4O3 could provide opportunities to further explore its potential applications.