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  • 1
    Electronic Resource
    Electronic Resource
    Transport critical current density and microstructure in extruded YBa2Cu3O7−x wires processed by zone melting (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 228-232 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: YBa2Cu3O7−x compounds were extruded into long wires with the diameter of 1 mm after sintering. The sintered wires were subsequently zone melted to develop a highly textured microstructure. Magnetization experiments at 77 K indicated a Jc value of 1×105 A/cm2 at 1 T. Transport measurements at 77 K showed a greatly enhanced field dependence of the critical current density. Transmission electron microscopy revealed an important grain-boundary feature which eliminated the weak-link behavior. Large amounts of dislocations have also been found in the zone-melted sample which may contribute to flux pinning in the system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347122
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  • 2
    Electronic Resource
    Electronic Resource
    Properties and chemical stability of hot-rolled Ag(7 at. % Cu)-sheathed Bi2Sr2Ca0.64Cu1.64Ox powder-in-tube tapes (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 4596-4607 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Bi2Sr2Ca0.64Cu1.64Ox (nominally Bi2212) powders were fabricated into powder-in-tube Ag- and Ag(7 at. % Cu)-sheathed tapes by cold and hot rolling to investigate the effects of sheath composition and rolling conditions on their microstructural development and superconducting properties. Bi2212 tapes with Ag(Cu) sheaths exhibited improved grain alignment and interfacial uniformity, as well as enhanced formation of the Bi-free phase (≈Sr7.5Ca6.5Cu14Ox), relative to the Ag-sheathed specimens. The hot-rolled Ag(Cu)-sheathed tapes displayed superior critical current densities (Jc), where magnetization Jcm=1.5×106 (H(parallel)c) and 4.6×105 A/cm2 (H⊥c) at T=5 K, H=1 T. Correspondingly, these specimens had transport critical current densities (Jct) of 6.7×104 A/cm2 (H(parallel)c) and 5.4×104 A/cm2 (H⊥c) at T=4.2 K, H=0 T and 2.2×104 A/cm2 (H(parallel)c) and 3.0×104 A/cm2 (H⊥c) at T=4.2 K, H=14 T. The chemical stability of the Ag(Cu) sheath regions during the partial melting process was also studied. Rapid oxidation of copper produced Cu2O precipitates in the sheath at 885 °C, and subsequently a Cu2O-free zone developed near the core/sheath interface. A theoretical analysis of Cu2O precipitate formation and decomposition during thermal processing is presented. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359805
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  • 3
    Electronic Resource
    Electronic Resource
    Reactivity and passivation for Bi adatoms on YBa2Cu3O6.9 and Bi2Ca1+xSr2−xCu2O8+y (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1004-1006 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: X-ray photoemission spectroscopy was used to examine the reactivity of clean YBa2Cu3O6.9 and Bi2Ca1+xSr2−xCu2O8+y surfaces with adatoms of vapor-deposited bismuth. For YBa2Cu3O6.9, depositions ≤8 A(ring) of Bi induce O 1s, Cu 2p3/2, and Bi 4f line-shape changes due to BiO bonding, limited oxygen loss from the substrate, partial conversion of Cu2+ to Cu1+, and growth of Bi metal. For coverages greater than 8 A(ring), there is no reaction and only Bi metal growth is observed. For Bi deposition onto Bi1Ca1+xSr2−xCu2O8+y, there is minimal reaction with only subtle O 1s and Cu 2p3/2 line-shape changes and the nucleation and growth of Bi metal starting at low coverages (≥2 A(ring)). Comparison shows that Bi is less reactive than other metals, except Ag and Au, and that Bi2Ca1+xSr2−xCu2O8+y is more stable toward Bi deposition than YBa2Cu3O6.9.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100650
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  • 4
    Electronic Resource
    Electronic Resource
    rf properties of an oxide-superconductor half-wave resonant line (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 930-932 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Cylindrical rods of YBa2Cu3O7−δ from 0.6 to 1.9 mm in diameter and up to 565 mm long have been used as the center conductor of a half-wave resonant coaxial line. The resonant line can be immersed in liquid nitrogen, which provides excellent cooling of the current-carrying superconducting surface, even in the presence of substantial rf losses. Such superconducting resonant lines have been operated at frequencies of a few hundred MHz and at rf surface magnetic fields up to 150 G at 77 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99277
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  • 5
    Electronic Resource
    Electronic Resource
    Single-crystal YBa2Cu3O7−x and Bi2Ca1+xSr2−xCu2O8+y surfaces and Ag adatom-induced modification (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 3130-3135 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Comparison of x-ray photoemission results for single crystal and polycrystalline YBa2Cu3O7−x allows us to identify oxygen vacancies in the Cu-O chains and determine their effects on the Cu, Ba, and Y core level line shapes. The deposition of adatoms of Ag onto single crystals of YBa2Cu3O7−x and Bi2Ca1+xSr2−xCu2O8+y leads to changes in the Cu 2p3/2 emission indicative of slight Cu2+ to Cu1+ surface reduction, with greater modification for the 1-2-3's than the 2-1-2-2's. O 1s core level results show Ag-induced broadening because of these surface effects. The Ba 3d and Y 3d structures showed minimal changes for the 1-2-3 surface. Ag deposition onto the 2-1-2-2 samples also leads to Bi dissociation and subsequent surface segregation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342709
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  • 6
    Electronic Resource
    Electronic Resource
    A time-temperature-transformation diagram for the orthorhombic to tetragonal phase transition in YBa2Cu3O7−∂ (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 5411-5414 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An isothermal transformation curve marking the orthorhombic (O) to tetragonal (T) phase transition boundary has been established over a wide temperature range. There exists within the time-temperature-transformation diagram two distinct and separate regions containing superconducting samples with narrow 90- and 60-K transition temperatures, respectively. An oxygen diffusion coefficient at 300 °C in these materials is estimated based on isothermal data. The kinetic process of the T-O transformation is studied. It is found, at all temperatures investigated, that extended annealing reduces the normal-state conductivity of the material and that the best samples are produced for intermediate annealing times.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340360
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  • 7
    Electronic Resource
    Electronic Resource
    Flux pinning in hot isostatically pressed Bi2Sr2CaCu2Ox (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 2823-2825 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic hysteresis data were taken from 4.2 to 35 K on Bi2Sr2CaCu2Ox samples that were hot isostatically pressed at 105 MPa in an inert atmosphere at 825 °C. One set of samples was pressed for only 15 min while the other was pressed for 120 min. The samples pressed for 15 min contained a high density of dislocations and planar faults, while the samples pressed for 120 min contained fewer dislocations and faults, with most dislocations present within subgrain boundaries. The samples with the complex dislocation/planar fault structures exhibited substantially larger hysteresis loops, suggesting enhanced flux pinning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108049
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  • 8
    Electronic Resource
    Electronic Resource
    Tracer diffusion of 110Ag in Bi2Sr2CaCu2Ox (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 2291-2293 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Tracer diffusion of 110Ag in dense polycrystalline Bi2Sr2CaCu2Ox has been measured at temperatures from 600 to 800 °C at an oxygen pressure of 105 Pa, and in oxygen partial pressures from 103 to 105 Pa at 700 °C. The diffusivity of Ag in Bi2Sr2CaCu2Ox is given by D=(8.9−4.2+7.9)exp[−(181.4±4.8 kJ/mol)/RT] cm2/s, and is not a sensitive function of oxygen partial pressure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107033
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  • 9
    Electronic Resource
    Electronic Resource
    Flux creep and pinning potential distribution in zone-melted YBa2Cu3Ox (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 225-227 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic relaxation data have been taken on zone-melted and sintered YBa2Cu3Ox samples over wide temperature and magnetic field ranges. We have found that magnetic relaxation varies greatly in the samples with different microstructures and crystallographic orientations. Flux-creep rates have been found to be reduced in the zone-melted samples owing to large amounts of intragranular crystal defects such as edge dislocations and stacking faults. An important flux-pinning behavior related to the pinning potential distributions has been observed in the samples. The relationship between microstructural orientation and pinning potential distributions in YBa2Cu3Ox is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105973
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  • 10
    Electronic Resource
    Electronic Resource
    Influence of oxygen concentration on processing YBa2Cu3O7−x (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 2485-2488 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The sintering kinetics of YBa2Cu3O7−x have been studied from 870 to 930 °C in oxygen/argon mixtures ranging from 0.2% to 100% oxygen. For sintering at temperatures below that required for formation of any liquid phase, densification rates increased with decreasing oxygen concentration, and transport critical current densities increased with increasing density. The activation energy for sintering was 190±30 kJ/mol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344260
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