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  • 1
    ISSN: 1572-9605
    Keywords: Epitaxy ; Thin Film ; Superconductor ; Critical Current Density ; RABiTS ; Buffer Layers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Epitaxial film growth of Tl0.78Bi0.22Sr1.6Ba0.4Ca2Cu3O9 ((Tl,Bi)-1223) on rolling assisted biaxially textured substrates with YSZ and CeO2 buffer layers (RABiTS) has been successfully demonstrated by laser ablation and post-deposition annealing in flowing argon. X-ray diffraction (XRD) θ-2θ spectra showed that the films consisted mainly of c-axis aligned 1223 phase with some intergrown 1212 phase, while XRD Φ-scans of (102) pole figure revealed that the films are also a- and b-axes aligned, with an epitaxy of the «100» of (Tl,Bi)-1223 film on the «110» of the top YSZ buffer layer. Four-terminal electrical transport measurements showed that the zero-resistance transition temperature (Tc) was in the range of 106 - 110 K, and the critical current density (Jc) at 77 K and zero field was about 105 A/cm2 for the entire film width (3 mm) of a longer film (14 mm) which was processed differently from the shorter films (7 mm). For a shorter film (7 mm) that showed better ab-in-plane alignment, the magnetization Jc, at 77 K and extrapolated to zero field, calculated from Bean's model using the full film width (3.5 mm) as the appropriate lateral dimension, was 2 × 105 A/cm2.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-9605
    Keywords: YBa2Cu3O x tapes ; RABiTS ; high critical current density
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Progress in the fabrication of epitaxial, high-J c, biaxially aligned YBCO thick films on Rolling-assisted biaxially textured substrates (RABiTs) is reported. RABiT substrates comprise a biaxially textured metal substrate with epitaxial oxide buffer layers suitable for growth of superconductors. Oxide buffer layers have been deposited using three techniques: laser ablation, electron-beam evaporation, and sputtering. Epitaxial YBCO films grown using laser ablation on such substrates have critical current densities approaching 3 × 106 A/cm2 at 77 K in zero field and have field dependences similar to epitaxial films on single crystal ceramic substrates. Critical current densities in excess of 0.2 MA/cm2 have been obtained on stronger, nonmagnetic substrates. In addition, samples with J e of 12.5 kA/cm2 at 77 K have been fabricated. The highest strain tolerence obtained so far is 0.7% in compression and 0.25% in tension. Deposited conductors made using this technique offer a potential route for the fabrication of long lengths of high-J c wire capable of carrying high currents in high magnetic fields and at elevated temperatures.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of superconductivity 6 (1993), S. 185-189 
    ISSN: 1572-9605
    Keywords: Thallium cuprates ; superconductivity ; magnetic hysteresis ; irreversibility ; flux pinning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract dc magnetic hysteresis as well as flux penetration and flux expulsion were investigated in Tl2−y Ba2CaCu2O8−x polycrystals and monocrystals. All measurements were performed at 35 K and in the 0–5 T field range. Hysteresis measurements revealed an irreversibility field of about 2 T. Existing models predict identical field-cooled (fc) and zero-field-cooled (zfc) magnetizations and vanishing time dependence above this field. Although the identical fc and zfc magnetizations are in fact observed, the time dependence vanishes only for flux penetration after zero-field cooling; a remanence is preserved after field cooling and decays with a finite relaxation rate. Activation energies calculated on the basis of the thermal activation model display a pronounced field dependence, and arelower for flux penetration than for flux expulsion in high fields (H≥3 T) for all orientations. This behavior of extreme layered superconductors contradicts classical theoretical models and questions the original definition of the irreversibility line as well. All of our results are consistent with the recent theory of lock-in transition, and can be well interpreted by using those principles.
    Type of Medium: Electronic Resource
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