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Applied Superconductivity, IEEE Transactions on

Issue 1  Part 3 • Date March 2001

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Displaying Results 1 - 25 of 325
  • 2000 Applied Superconductivity Conference

    Publication Year: 2001
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    Freely Available from IEEE
  • Characterizations of CeO/sub 2/ and BaTiO/sub 3/ double buffer layer for the growth of Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-x/ superconducting thin film

    Publication Year: 2001 , Page(s): 2719 - 2722
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    High quality Y1Ba2Cu3O7-x(Y-Ba-Cu-O) superconducting thin films have been grown on metallic Hastelloy(Ni-Cr-Mo alloys) substrates with Ce02, BaTi03, and Ce02/BaTiO3 buffer layers in-situ by pulsed laser deposition. Ce02 layer revealed that (200) XRD peak became dominant at a specific deposition temperature but the grain size of that film was observed to be small. BaTi03 has shown larger grain size than that of CeO2 by 200 times. Two buffer layers have been integrated to enhance the superconducting properties of Y-Ba-Cu-0 thin film on metallic substrate. This Y-Ba-Cu-O/Ce02/BaTiO3 on metallic substrate shows enhanced superconducting properties of the transition temperature of 85 K and the critical current density of about 8.4 × 104 A/cm2 measured at 77 K mainly due to the enlargement of the grain size of Y-Ba-Cu-0 film with double buffer layer. View full abstract»

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  • High-quality HTS tiles designed for the application in magnetic bearings of cryotanks and flywheels

    Publication Year: 2001 , Page(s): 3728 - 3731
    Cited by:  Papers (7)
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    High quality bulk YBaCuO superconductors with maximum trapped fields up to 1.3 T and transport critical current densities up to 1.3 A/cm/sup 2/ in self field at 77 K are prepared by the Top Seeded Melt Growth. On the basis of this process two methods for the processing of large tiles and tiles in complex shapes are presented. Superconducting rings with a radial orientation of the crystallographic c-axis are processed by a multi-seeding method. These rings are used in the magnetic bearing of a cryotank designed for the storage of liquid hydrogen. The joining of single domains with an ErBaCuO compound leads to the formation of a superconducting joint between single domains. Large tiles prepared by this process are to be used in the circumferential magnetic bearing of a flywheel. View full abstract»

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  • Natural and artificial low angle grain boundaries with high current-carrying capabilities

    Publication Year: 2001 , Page(s): 3788 - 3791
    Cited by:  Papers (2)
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    For several years, the technical applications of bulk HTS YBCO superconductors are of growing interest. However, for applications which require a complex geometry of the monoliths, the Multi-Seeding Melt Growth (MSMG) and the mechanical joining of two single-domain tiles becomes necessary. However, these two techniques lead to the formation of a low-angle grain boundary (GB). The influence of the seed distance (d/sub s/) on the properties of the GB has been studied in order to obtain a precipitate free grain-boundary. On the top surface of one monolith, two distances between two seeds were chosen, i.e. 4 mm and 11 mm. Regarding d/sub s//spl sim/11 mm, some rich-copper phases and large pores can be observed throughout the GB. In contrast, for d/sub s//spl sim/4 mm, neither residual copper-rich phases nor pores are observed within the GB. Magneto-optical measurements performed on the sample with d/sub s//spl sim/4 mm, revealed that the critical current density through the GB is influenced by the growth directions. Regarding the mechanical joining, a high connectivity between two adjacent domains can be obtained by using the PLD technique for coating of the monoliths. View full abstract»

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  • Conference Author Index

    Publication Year: 2001 , Page(s): 3989 - 4006
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    Freely Available from IEEE
  • Critical current hysteresis in low angle Y-Ba-Cu-O bicrystals

    Publication Year: 2001 , Page(s): 3776 - 3779
    Cited by:  Papers (2)
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    We study the transport critical current of c-axis YBCO films grown on low angle [001] tilt bicrystals of 2.5°, 5°, and 7.5°. The influence of low magnetic fields on each single grain boundary has been studied at different temperatures by varying the field direction in the plane of the boundary with the magnetic field always perpendicular to the bias current. The tilt angle, θ, between the magnetic field direction and the normal to the film surface has been varied from -110° to +110°, where 0° corresponds to the field direction parallel to the c-axis of the film. We find that the angular dependence of the critical current density Jc shows a hysteretic behavior for applied magnetic fields below 1 T. Maxima of Jc are observed at different angles depending on the rotation direction of the applied magnetic field. We notice that the angular difference between the critical current peaks is a function of the external magnetic field, so that for strong fields only the ±90° maxima are observed. We relate these observations to the intrinsic pinning between CuO layers, and to trapped flux in the superconducting film View full abstract»

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  • Investigation of the formation of the Bi-2223 phase in multifilamentary Bi-2223/Ag tapes by in situ high temperature neutron diffraction

    Publication Year: 2001 , Page(s): 3399 - 3402
    Cited by:  Papers (2)
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    Results of in-situ diffraction experiments in the investigation of multifilamentary Bi-2223/Ag tape superconductors with neutron radiation are reported. The aim is to characterise the formation reaction of the Bi-2223 phase and the changes in the secondary phases assemblage under real reaction conditions without removing of the silver sheath of the composite. Furthermore, the mechanism of the evolution of a fibre texture of the superconducting phases Bi-2212 and Bi-2223 are discussed. Additionally, the results of the in-situ diffraction experiments will be related to the characterisation of the microstructure of quenched specimens done by scanning electron microscopy. Finally, a reaction model of the formation of the Bi-2223 phase within the composite conductor will be discussed View full abstract»

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  • Suppression of flux jumps in marginally stable niobium-tin superconductors

    Publication Year: 2001 , Page(s): 3679 - 3682
    Cited by:  Papers (7)
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    Niobium-tin superconductor wires with coalesced filaments may have reduced adiabatic stability. Magnetization measurements on such marginally stable conductors exhibit flux jumps, which appear as a sudden decrease in magnetization as the applied field is changed, caused by the unpinning of flux vortices and resistive heat generation. Flux jumps preclude estimation of the hysteresis loss from the area of the magnetization-versus-field loop. Here, we show that flux jumps can be minimized or suppressed during the measurement of hysteresis loss by immersing the specimen in helium liquid instead of helium gas. The better thermal conductivity of the liquid affords additional dynamic stability against flux jumps. This allows one to determine the loss upon field cycling and to calculate an effective filament diameter, often used to gauge losses and the extent of metallurgical interfilament coupling View full abstract»

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  • Overpressure processing Bi2223/Ag tapes

    Publication Year: 2001 , Page(s): 3026 - 3029
    Cited by:  Papers (6)  |  Patents (1)
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    We report on the effect of overpressure processing on the electromagnetic properties and microstructure of monocore and multifilamentary Bi2223/Ag tapes. Samples at various stages of the usual thermo-mechanical processing for Bi2223/Ag tapes (from as-rolled to fully processed) were subjected to annealing at 815-820°C for 18-108 h in a static Ar+O2 atmosphere at the overall pressure 17.5±0.5 MPa (pO2= 0.003-0.02 MPa). Density measurements, microhardness tests, and SEM examination of polished sections reveal a notable densification of overpressure-processed samples. For partly reacted (so called HT1) samples, we found that overpressure processing for 36 h is sufficient to densify the Bi2223 core from 70±5 to 87±4% theoretical density and increase self-field Jc(77 K) from 8±1 to 30±5 kA/cm2 The results show that one-step processing of Bi2223/Ag tapes is possible View full abstract»

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  • Parallel and perpendicular field dependence of JC of NbTi-Cu multilayer films

    Publication Year: 2001 , Page(s): 3840 - 3843
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    The critical current density, JC, of NbTi-Cu multilayer films has been measured in parallel fields and in perpendicular fields at 4.2 K, as a parameter of thickness of the NbTi monolayer, ds . The thicknesses ns are 100 nm, 200 nm, 300 nm, and 500 nm, while the thickness of the Cu monolayer is 200 nm. It is found that the cross field B* where JC in perpendicular fields exceeds that in parallel fields clearly decreases as ds increases. As a result of analyses of scaling parameters, the pinning force density of NbTi-Cu multilayer films in both parallel fields and perpendicular fields may be explained by the scaling law as a parameter of thickness d s with different values of scaling parameters View full abstract»

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  • Test station for magnetization measurements on large quantities of superconducting strands

    Publication Year: 2001 , Page(s): 3086 - 3089
    Cited by:  Papers (6)
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    In the superconducting main magnets of the Large Hadron Collider (LHC), persistent currents in the superconductor determine the field quality at injection field. For this reason it is necessary to check the magnetization of the cable strands during their production. During four gears, this requires measurements of the width of the strand magnetization hysteresis loop at 0.5 T, 1.9 K, at a rate of up to eight samples per day. This paper describes the design, construction and the first results of a magnetization test station built for this purpose. The samples are cooled in a cryostat, with a 2-m long elliptic tail. This tail is inserted in a normal conducting dipole magnet with a field between ±1.5 T. Racetrack pick-up coils, integrated in the cryostat, detect the voltage due to flux change, which is then integrated numerically. The sample holder can contain eight strand samples, each 20 cm long. The test station operates in two modes: either the sample is fixed while the external field is changed, or the sample is moved while the field remains constant, First results of calibration measurements with nickel and niobium are reported View full abstract»

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  • Effect of oxygen content on flux pinning in Nd-Ba-Cu-O single crystals

    Publication Year: 2001 , Page(s): 3639 - 3642
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    The magnetization of NdBa2Cu3Oy single crystals with various oxygen contents was investigated by superconducting quantum interference device (SQUID) magnetometer over a wide range of temperature and field. The results clearly indicate that the peak effect and flux pinning can be easily adjusted by changing the oxygen content in this material. Although the peak field decreases with increasing the amount of oxygen vacancies, Jc is significantly improved in the low fields and the peak effect becomes more pronounced. The oxygen vacancy clusters are very effective pinning centers and dominate the flux pinning in the sample subjected to the annealing and quenching process at 400°C View full abstract»

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  • Cu-added Nb3Al multifilamentary superconductors having high Jc in high fields

    Publication Year: 2001 , Page(s): 3976 - 3979
    Cited by:  Papers (5)
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    The RHQT (rapid heating, quenching and transforming)-processed Nb 3Al multifilamentary wire shows not only excellent strain tolerance but also 2-5 time higher Jc than those of the commercialized Nb3Sn multifilamentary wires, and is being developed as a new practical superconductor. When the Nb/Al-2at%Cu microcomposite wire was rapidly heated and quenched, disordered A15 phase filaments were formed directly in stead of Nb-Al bcc supersaturated phase filament formation in the normal RHQT-process. With annealing at 700-800°C, its superconducting properties were improved drastically. The Cu-added Nb3Al multifilamentary wire showed the maximum values of Tc=18.6 K and Hc2(4.2 K)=28.7 T, which are higher than the maximum values of Tc=17.9 K and Hc2(4.2 K)=25.8 T for the RHQT-processed Nb3Al wire without Cu addition. In addition the new Nb3Al superconductor showed higher Jc than that of the RHQT-processed Nb3Al wire in high fields above 18 T. The maximum Jc is 360 A/mm2 at 4.2 K and 21 T View full abstract»

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  • Growth of Hg0.8Pb0.2Ba2Ca2 Cu3O8+δ thick films on Ag using a modified process route

    Publication Year: 2001 , Page(s): 3118 - 3121
    Cited by:  Papers (1)
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    Thick films of Hg0.8Pb0.2Ba2Ca 2Cu3O8+δ (HgPb1223) superconductor were fabricated by dip-coating Pb0.2Ba2 Ca2Cu3O7+δ precursor onto Ag and subsequently reacting in Hg vapor to form the superconducting phase. It was found that by “burying” the films in precursor powder during the reaction, increased HgPb1223 phase purity and increased size of aligned grain colonies were obtained. Such microstructural improvements lead to wider magnetization hysteresis. The optimum superconducting transition temperatures of 133 K were observed in these films. The results showed that this process has a positive influence on the formation and growth of HgPb1223. A pre-pressing process enabled the growth of HgPb1223 grains with relatively dense microstructure and improved connectivity. The resulting films exhibited a transport Jc value of at least 1.5×103 A/cm2 at 4.2 K in a zero magnetic field View full abstract»

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  • Texture development in IBAD MgO films as a function of deposition thickness and rate

    Publication Year: 2001 , Page(s): 2822 - 2825
    Cited by:  Papers (25)  |  Patents (1)
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    We have examined the effect of film thickness on in-plane texture for ion-beam assisted deposition (IBAD) of MgO films. Plan-view dark-field transmission electron microscopy (TEM) has revealed that texture develops rapidly, reaching its best value at a critical thickness of~10 nm. These results have been confirmed by quantifying the in-plane texture of these samples at each thickness with X-ray diffraction φ-scans. We have also examined the effects of variable deposition rate on texture formation. X-ray diffraction shows that the optimum in-plane texture is achieved at the critical thickness with a rate of 0.2 nm/s. However, TEM imaging has shown that the distribution of well-aligned grains decreases with an increase in rate. As such, deposition at 0.1 nm/s was found to be sufficient for achieving good in-plane distribution values and good surface coverage for subsequent depositions. By combining the results of both of these experiments, we were then able to optimize our deposition process and apply them to the growth of IBAD MgO on metal substrates View full abstract»

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  • Influence of dynamic and static stresses to mechanical and transport properties of Ag/Bi2223 composite superconductors

    Publication Year: 2001 , Page(s): 3022 - 3025
    Cited by:  Papers (12)
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    Mechanical properties under static stress of Bi2223 monofilamentary tapes are characterized. The narrow true elastic region (stage I) is followed by the stage II, where a gradual decrease of the slope of stress-strain curve was observed, accompanied by voltage increase. This suggests that a number of microcracks are generated over the whole specimen and a few of them grow in macroscopic scale. The macroscopic yielding and the multiple fracture take place in the oxide layer (stage III). During the fatigue test, the V-I curves were measured at zero load and the n-value was determined. For stage II, the critical current decreased greatly after one cycle and decreased gradually over several hundred cycles, then reached to a non-zero constant value depending on the applied maximum stress. Applying the two phase model, the change of stress level induced in each component has been assessed View full abstract»

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  • Current density distribution in BSCCO-2223 tapes in overload conditions

    Publication Year: 2001 , Page(s): 2749 - 2752
    Cited by:  Papers (3)
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    The current density distribution in HTS tapes for power transmission applications plays a key role for the determination of the conductor dissipation both in normal and in overload conditions, as occurring for example during transmission lines faults. We have tested the response of Ag/Bi2223 tapes in dc and ac self field transport current in order to determine the repartition of current between the superconducting material and the silver sheath, in particular in the high current range. The experimental results are compared with the results of a numerical calculation model able to determine the tapes self-field current density distribution both above and below Ic. The same model is also used to calculate the tape's AC losses. The results are compared with the measured values View full abstract»

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  • Relation between texture and critical current density of textured YBa2Cu3Ox plates

    Publication Year: 2001 , Page(s): 3513 - 3516
    Cited by:  Papers (1)
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    Textured YBa2Cu3Ox plates show a significant spread in the critical current density up to 12.000 A/cm2 measured by direct transport current at 77 K. This spread is related to the crystalline texture of the material. Optical polarization microscopy is used for initial examination of crystal alignment and texture. We use synchrotron radiation at 100 keV to perform x-ray diffraction measurements to obtain quantitative information about the texture. The crystallographic (110)-direction is found to be preferentially along the slab and the c-axis is parallel to the largest face. DC-magnetization is used to measure the magnetization critical current density of pieces cut around each x-ray measurement point. The results from x-ray diffraction, optical microscopy and magnetization critical current density are compared to the transport critical current density. The magnetization critical current is found to decrease exponentially with the in-plane texture View full abstract»

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  • Construction of the magnetic phase diagram in small-volume HTS by an OFC magnetometer

    Publication Year: 2001 , Page(s): 3931 - 3934
    Cited by:  Papers (1)
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    We applied the OFC magnetometer for studies of vortex dynamics in small-volume HTS. The substitution of the solenoid coil by a flat one in a tunnel diode oscillator made the coil's filling factor maximal for flat specimens enabling to reach 1-3 Å absolute and 10-6 relative changes of the penetration depth, λ, of RF magnetic field into HTS films. Our technique operates in high magnetic fields and measures linear changes of λ in 1 mm range with high resolution. It is also an excellent Q-meter for detection of changes ~10-9 W of the absorption in HTS samples. Such abilities allow it to be applied in many fields of science and technology. In particular, detection of the magnetic field-dependent changes of the frequency and amplitude of a 23 MHz oscillator enabled lines on the magnetic phase diagram for Y-Ba-Cu-O film to be constructed. It seems to have many similarities as compared to the diagrams defined for bulk HTS by other methods. However, how close the relation is in fact, may be revealed after additional tests on the same quality specimens View full abstract»

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  • Development of nickel alloy substrates for Y-Ba-Cu-O coated conductor applications

    Publication Year: 2001 , Page(s): 3321 - 3324
    Cited by:  Papers (10)
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    Fabrication of long-length, textured substrates constitute a critical step in the successful application of coated High Temperature Superconductors (HTS). Substrate materials stronger than nickel are needed for robust applications, while substrates with non-magnetic characteristics are preferred for AC applications. The present work is thus focused on development of texture in high strength, non-magnetic substrate materials. As the development of cube texture is easier in medium to high stacking fault energy materials, binary alloys based on nickel were evaluated for the present application. High purity alloys were melted and hot/cold worked to obtain thin tapes. The development of texture in these alloys as a function of processing parameters was studied by X-ray diffraction and metallographic techniques. Orientation Imaging Microscopy (OIM) was used to quantify the extent of texture development in these substrates. Results to date on the development of texture by thermo-mechanical processing of these alloys are presented View full abstract»

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  • Growth of large area YBa2Cu3O7-x thin film by cylindrical hollow cathode sputtering

    Publication Year: 2001 , Page(s): 3844 - 3847
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    We have deposited large area YBa2Cu3O7-x thin films by cylindrical hollow cathode sputtering using a 9 cm diameter hollow cathode sputtering gun. The zero resistance temperature of the films at the center and edge were in the range from 86 K to 83 K. X-ray diffraction analysis and scanning electron micrographs showed that the films are completely c-axis oriented. The variation of the thickness was less than 5% over the whole substrate. The values of microwave surface resistance were 1 mΩ at 25 K and 40 mΩ at 77 K and 19.6 GHz View full abstract»

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  • Current and temperature controlled variable inductance in superconducting microstrip lines

    Publication Year: 2001 , Page(s): 3090 - 3093
    Cited by:  Papers (1)  |  Patents (1)
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    The inductance of superconducting microstrip lines is measured both as a function of current and temperature. The measurements are performed at 10 MHz for both meander and straight lines by using a multi-frequency LCR meter. The normal state resistance is observed to follow a linear temperature dependence with a slope of 3.59×10-3/K for the straight line and with a slope of 2.96×10-3/K for the meander line. The change in inductance is well described by a quadratic dependence on temperature. This result is consistent with an unconventional pairing state. As for the dependence on the bias current, the inductance shows a squared dependence on the bias current. The results for the current- and temperature-controlled inductance are in good agreement with an equation derived using the Ginzburg-Landau theory for the case of thin films View full abstract»

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  • High performance superconducting Y-Ba-Cu-O tapes produced by oxidation of metallic precursors

    Publication Year: 2001 , Page(s): 2901 - 2904
    Cited by:  Papers (3)
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    A metallic precursor fabrication route has been developed for the production of multifilamentary tapes of textured YBa2Cu3 O7-δ in a silver matrix. The number of filaments in prototype tapes ranged from 10 to 1024 with filament thickness from 1 to 40 microns. Following low temperature oxidation of the metallic precursor, we explored conditions for YBa2Cu3O7-δ formation similar to those used in the growth of epitaxial thin films. The YBa2Cu 3O7-δ phase was observed to grow near the Cu I/CuII boundary. The growth step was followed by a low temperature anneal in one atm of oxygen. Jc and Tc values were found to depend strongly on processing conditions. With optimum processing, a Tc of 90 K and a Jc of 20kA/cm2 at 65 K, were measured. XRD patterns of chemically etched surfaces of the processed tapes gave some evidence for epitaxial alignment of the YBa2Cu3O7-δ with the pre-textured silver matrix View full abstract»

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  • Growth mechanism of YBa2Cu3O7-y thin films on the metallic tapes by MOCVD

    Publication Year: 2001 , Page(s): 3453 - 3456
    Cited by:  Papers (2)
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    We fabricated a YBa2Cu3O7-y (YBCO) thin film on an MgO single crystalline substrate and cube textured (CUTE-Ag)-tapes using metal organic chemical vapor deposition (MOCVD). It was confirmed that a c-axis oriented YBCO film grew on these substrates. The terraced surface and spiral growth pattern are clearly visible. Many Ag particles were observed on the terrace surface of the spiral steps. After heat treatment these particles concentrated at the edge of the spiral steps. The dependence of the terrace width on the substrate temperature is drastically changed at the certain temperature range between 750 and 800°C. At high temperatures, the terrace width of the films on MgO increases and reaches about 90 nm at 800°C, whereas those on CUTE-Ag tape have a terrace width of about 160 nm at the same temperature. The values of the supersaturation ratios are estimated as 50 and 15 from the terrace widths on MgO and CUTE-Ag. The results from the surface morphology and the microstructure suggest that there is a difference in the growth mechanism between the YBCO films on MgO and those on CUTE-Ag in the higher temperature region. We speculate that the quasi-liquid layer is more stable on the CUTE-Ag at higher temperatures than 750°C, and the growth mechanism of the YBCO films on the CUTE-Ag is mixed with the Vapor-Liquid-Solid (VLS) growth mode and the surface-active species (Surfactants) growth mode View full abstract»

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  • Reel to reel continuous formation of Y-123 coated conductors by IBAD and PLD method

    Publication Year: 2001 , Page(s): 2816 - 2821
    Cited by:  Papers (22)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    Continuous deposition of Y-123 tapes was performed by ion-beam-assisted deposition (IBAD) and pulsed laser deposition (PLD) method. YSZ template films were deposited by IBAD on Ni-based alloy tapes with tape shifting speeds of 0.1-0.3 m/h. They were uniformly coated with an in-plane mosaic spread of 12-13 degrees in 5 m length. In order to overcome the low deposition rate of the IBAD process, large area ion sources with inductively coupled discharge plasma were applied. Y-123 films were deposited by PLD on the YSZ templates with a tape shifting speed of 1.0 m/h. The degradation of Y-123 targets for the PLD process was effectively restricted by combined motion of rapid rotation and linear shifting. Ic of 84.0 A and Jc of 0.76MA/cm2 were obtained at 77 K, 0 T in the length of 1.0 m when the in-plane mosaic spread for the Y-123 film was 7 degrees. Ic of 35.0 A and Jc of 0.25MA/cm2 were obtained in a 4.6 m long sample at the length of 4.0 m, when the in-plane mosaic spread for the Y-123 film was 11 degrees View full abstract»

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IEEE Transactions on Applied Superconductivity contains articles on the applications of superconductivity and other relevant technology.

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Editor-in-Chief
Britton L. T. Plourde
Syracuse University
bplourde@syr.edu
http://www.phy.syr.edu/~bplourde