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  • 1
    Electronic Resource
    Electronic Resource
    Transport and magnetic properties of high-Tc YBa2Cu3O7−x films (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3772-3774 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin superconducting films of YBa2Cu3O7−x were deposited onto (100) SrTiO3 substrates at 750 °C in 100 and 200 mTorr of O2, by ArF excimer laser ablation. The as-deposited films were strongly oriented with the c axis perpendicular to the surface when they were cooled to room temperature in oxygen. The highest values of transport critical current density (Jc(approximately-greater-than)105 A/cm2 below 80 K) were observed in films cooled in flowing O2. We find that, in all films, Jc follows a power law (1−T/Tc)n with n≈2, near the critical temperature, Tc, when Tc is defined as the temperature at which Jc=0. It appears that this behavior is governed by the short coherence lengths in this high-Tc material, as suggested by G. Deutscher and K. A. Müller [Phys. Rev. Lett. 59, 1745 (1987)], and not by the specific nature of the large-scale structure of the films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346301
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  • 2
    Electronic Resource
    Electronic Resource
    Preparation and characterization of superconducting phases in the Bi(Pb)-Sr-Ca-Cu-O system (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 3717-3722 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The superconductive properties in the Bi(Pb)-Sr-Ca-Cu-O system with nominal composition of Bi2−x Pbx Sr2 Ca2 Cu3 Oy (x=0, 0.2, 0.4, and 0.6) and annealed at 860 °C for 240 h were studied using dc resistivity and ac susceptibility measurements. For x=0.2 and 0.4, the bulk zero resistivity temperatures were found to be ∼103 K. For x=0 and 0.6, these temperatures were found to be ∼73–75 K. The ac susceptibility data show enrichment of the volume fraction of the high-Tc phase in compositions with x=0.2 and 0.4. Tc of this phase is constant at 107 K for all values of x. The enhancement of the bulk zero resistivity temperature for x=0.2 and 0.4 is due to the improved intergranular coupling of the high-Tc phase, although the resulting weak-link behavior reflects a low current carrying capacity in these materials. The presence of the low-Tc phase (∼65 K) is still visible in the susceptibility data. For x=0.6, the intergranular coupling of the high-Tc phase is almost destroyed; however, the coupling of the low-Tc phase is better than when x=0. Powder x-ray diffraction and scanning electron microscopy data show the formation of large grains of the calcium plumbate, Ca2PbO4 phase with increasing Pb up to x=0.6. The large grains of the Ca2 PbO4 phase may incorporate other impurity phases within it when x=0.6, cleaning up the remaining grain boundaries, thereby improving the intergranular coupling within this material. Energy dispersive x-ray analysis indicates that some Pb is incorporated into the structure of both superconducting phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344056
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  • 3
    Electronic Resource
    Electronic Resource
    Dependence of transport critical current density on sample size for ceramic RBa2Cu3O7−x (R≡Y, Ho, Gd) (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 5510-5513 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements of the transport critical current density Jc were carried out on sintered and partially melted samples of YBa2Cu3O7−x , YBa2Cu3O7−x +Ag, HoBa2Cu3O7−x, and GdBa2Cu3O7−x using a four-probe method and a contactless magnetic induction method. Results obtained by the two methods were in agreement. A pronounced dependence of Jc on sample cross-sectional area was observed for all samples: Jc increased with decreasing cross-sectional area. Values of Jc ranging from about 30 to 800 A/cm2 were measured depending on the preparation method and sample geometry. It is concluded that in view of the cross-sectional area dependence, comparison of Jc for different preparations should always be made for samples of similar geometry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343703
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  • 4
    Electronic Resource
    Electronic Resource
    The effects of long-term annealing on superconducting properties in the Bi-Sr-Ca-Cu-O system (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 2392-2397 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of long-term annealing on the relative proportions of the low- and high-Tc phases present in the Bi-Sr-Ca-Cu-O system was examined by resistivity and ac susceptibility measurements. The zero-resistivity offset was found to increase from 50 to 68 K and the susceptibility measurements showed the disappearance of the low-Tc , 63-K phase with the enrichment of the high-Tc , 110-K phase as a result of the annealing treatment. Also, the onset of diamagnetism of the high-Tc phase was enhanced by 3 K due to prolonged annealing. The high-Tc phase thus formed is poorly crystallized as determined by the x-ray diffraction patterns. Some impurities are observed in both x-ray diffraction patterns and scanning electron microscopy pictures and are assigned to the low-Tc , Sr, and Bi-doped Ca2CuO3 phases. This study shows that a complex ac susceptibility measurement technique can be a very powerful tool for studying the equilibrium superconducting phases present at a particular temperature in a multicomponent system such as Bi-Sr-Ca-Cu-O.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342806
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  • 5
    Electronic Resource
    Electronic Resource
    Influence of nickel substrate grain structure on YBa2Cu3O7−x supercurrent connectivity in deformation-textured coated conductors (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 2906-2908 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Coupled magneto-optical imaging and local misorientation angle mapping have been used to demonstrate the percolative nature of supercurrent flow in YBa2Cu3O7−x(YBCO) coated conductors grown on deformation-textured Ni substrates. Barriers to current flow occur at many YBCO grain boundaries (GBs) which have propagated through the buffer layers from the underlying Ni substrate, and all Ni GBs with misorientation angles 〉4° initiate percolative current flow. This type of current barrier is characteristic of the conductor form and has been found to exist in samples with Jc(0 T,77 K) values 〉2 MA/cm2. Sharpening of the local substrate texture or improving in low-angle GB properties should lead to higher Jc values. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1315631
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  • 6
    Electronic Resource
    Electronic Resource
    Fabrication and electrical properties of ceramic superconductor/polymer composites (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 305-309 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Superconductor/polymer composites were prepared by mixing powders representing the Y-Ba-Cu-O and Bi(Pb)-Sr-Ca-Cu-O systems with high-density polyethylene. Their electrical resistivities were measured as a function of temperature. By controlling the powder preparation techniques, it was possible to fabricate composites with superconductive transition to zero resistivity in the Bi(Pb)-Sr-Ca-Cu-O system. These composites can be fabricated in certain desired shapes.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320502
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