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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3122-3132 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structural properties of superconducting (Bi,Pb)2Sr2Ca2Cu3O10–Ag (2223) tapes have been measured using synchrotron x-ray scattering techniques. The x-ray photon energy was tuned just below the silver K absorption edge so the penetration depth was large, which allowed the measurements to be performed in a transmission geometry without removing the silver cladding. Analysis of the peaks in 2θ scans indicates that residual (Bi,Pb)2Sr2CaCu2O8 (2212) superconductor starting material is present in all samples studied. The amount of 2212 varied widely among the tapes, and was not homogeneous along the length of each individual tape. Residual 2212 content increased near the ends of most samples, suggesting that 2223 phase development is sensitive to whether the superconducting material is encased in silver or not. The bulk c-axis alignment was measured in ∼100 mono- and multifilament samples, and correlations between c-axis alignment and current carrying capacity at 77 K were found. Multifilament samples generally had better alignment than monofilament samples. The c-axis alignment along the length of the tapes was uniform, and the superconducting material within ∼1 μm of the Ag was better textured than the bulk of the sample. Intermediate pressings were directly shown to have an adverse affect on c-axis alignment. Finally, the evolution of texture and phase development was examined in a series of samples annealed for varying times. The 2212 starting material acquired the final c-axis alignment state after brief heating times, and only after much longer heating times did the 2212 transform into the 2223 phase. These results and their implications for improving processing procedures are discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 4584-4590 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Alternating current (ac) losses in silver sheathed mono- and multicored (Bi,Pb)2Sr2Ca2Cu3O10 superconducting tapes were investigated at liquid neon temperature (27 K) under various direct current (dc) background magnetic fields. The loss behavior was well accounted for by the Bean critical state model with the inclusion of eddy current loss in the silver sheath. The interfilamentary coupling loss was found to be negligibly small for the present orientation of the tape. In addition, a severe distortion of the loss signal and the B-H hysteresis curve was observed at 27 K when a high dc magnetic field was applied simultaneously with ac fields. The losses of the tapes were also measured at 77 K and compared with the 27 K values. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 331-335 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Effects of oxygen partial pressure PO2 during low temperature postheat treatments on the superconducting properties of silver-sheathed Bi2Sr2CaCu2Oy tapes were investigated. The critical temperature Tc of the resulting tapes changes systematically with PO2. This variation of Tc is attributed to the change of electronic carrier (hole) concentration by the observation of oxygen K-edge absorption spectra. The intragranular critical current density Jc is essentially unaffected by the heat treatment, while deterioration in grain connectivity is observed in the specimens treated in reduced-oxygen atmospheres. The change of anisotropy in Jc with respect to crystallographic orientations is also quite small for the variation of PO2. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 2709-2717 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Alternating current losses in stacks of powder-in-tube-processed Bi2Sr2Ca2Cu3O10/Ag tapes were measured in perpendicular magnetic fields and compared with calculated hysteresis losses based on the critical-state model. Four main factors had to be taken into account for the calculations of the losses: (1) the inclusion of the area of the Ag sheath in determining the critical-current densities of the stacks, (2) the zero-applied-field critical currents Ic⊥(0) with truly perpendicular fields only, not the standard self-field critical current IcS(0), and (3) the field-dependent critical current Ic(H), e.g., the Kim's model, and (4) the subtraction of the frequency-dependent losses at very high fields. With these considerations, the agreement between the calculated and the measured values of the losses is excellent for fields beyond the full-penetration fields. However, these factors did not totally account for the low-field losses. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 3407-3410 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the effects of ozone oxygenation of YBa2Cu3O7−δ thin crystals for eliminating local fluctuation in oxygen content, which is known to exist even in normal δ≈0 samples. An optimum ozone annealing condition was determined based on the microstructure and the uniformity of oxygen content of the samples. We observed the formation of fine-spacing twins running perpendicular to the original twins at thin areas and attributed this to accommodating the local strain due to oxygen uptake during ozone annealing.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 4409-4414 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A magneto-optic imaging technique was used to examine the flux distributions at 50, 60, and 70 K in a single-crystal platelet of YBa2Cu3O7. The superconducting sample was covered with a layer of iron garnet film, and a polarization microscope was used to examine the magnetic domains in this imaging film. Since the spacing of these domains was proportional to the local magnetic field in the underlying superconductor, it was possible to determine field profiles directly from the optical density of the image. Field profiles indicated that the distributions of remnant flux in the sample were well described by the critical state model. It was also possible, through the use of simple linear models of initial flux penetration, to measure the flux trapped in the sample as a function of time. The flux creep data derived from analysis of the digitized images showed a logarithmic decrease of magnetization with time, in good agreement with SQUID magnetometer measurements performed on the sample. There was no evidence of an axial critical state.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5461-5462 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dc hysteresis behavior of the magnetization and the 60-Hz ac loss characteristics were both measured at 4.2 K as a function of applied field to 2000 Oe on Yba2Cu3O7 and on iron-substituted YBa2(Cu1−xFex)3O7 samples with x=0.04 and 0.10. From the dc hysteresis behavior, energy loss per cycle was found to decrease with increasing Fe content. On the other hand, replacing copper with iron up to 4% did not change the 60-Hz loss, but increasing the iron content up to 10% was found to increase the loss by a significant amount.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3180-3182 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: ac losses at 60 Hz have been measured for silver-sheathed (Bi,Pb)2Sr2Ca2Cu3O10 multifilamentary tapes at 27 and 77 K to investigate the role of interfilamentary coupling. The results are qualitatively well described by the use of the concept of the critical coupling length lc. Further, it is shown that to obtain effective reduction of the coupling loss, a very small twist pitch length ((very-much-less-than)1 cm) as well as a substantial reduction in the filament thickness are required for an applied ac field of, for example, 100 rms A/cm at 77 K. © 1995 American Institute of Physics. [S0003-6951(95)02147-5]
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3025-3027 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Improved strain sensitivity of critical currents Ic of the multicored over the monocored (Bi,Pb)2Sr2Ca2Cu3O10–Ag tapes is shown for bending strains, but not for axial tensile strains. The improved mechanical tolerance is due, in part, to a better alignment of the Bi-cuprate platelets achieved in the multicored tapes. Furthermore, the difference in the response to these tapes to axial tensile and bending strains is due to the difference in the precise manner in which the strains are applied to the tapes. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 2653-2655 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Plasma-sprayed YBa2CU3Oy coatings consist of a nonsuperconducting tetragonal phase with an a/c ratio of 1/3 (c=11.61) in the as-sprayed condition. This phase is tentatively assigned to the solid solution Y1(Ba2−xYx) Cu3O7+δ. Heat treatment of this phase at 930 °C/24 h in oxygen results in orthorhombic symmetry, an expansion of the c axis (11.66 A(ring)), and the appearance of superconductivity. In this study it is shown that heat treatment in argon at 850 °C prior to the oxygen heat-treatment leads to a crystal structure which closely matches the desired YBa2Cu3Oy (c=11.68), raises Tc, and narrows the transition width.
    Type of Medium: Electronic Resource
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