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  • 1990-1994  (3)
  • 1991  (3)
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  • 1990-1994  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    Synthesis of superconducting La2−xSrxCaCu2O6 using O2-hot-isostatic-pressing techniques (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 3190-3193 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Superconducting 326 samples, La2−xSrxCaCu2Oz with x=0.2 and 0.4, which exhibited superconducting onsets at temperatures (Tonc's) higher than 40 K were successfully synthesized using hot-isostatic-pressing (HIP) techniques. As starting materials, powders of conventional carbonates (SrCO3 and CaCO3) and oxides (La2O3 and CuO) were employed. Sintering of the samples was made at a variety of temperatures (Ts) for 72 h in flowing O2 gas (of 1 atm). The sintered samples were post-annealed at various temperatures (Ta) for 6 h in a mixture of 80% Ar gas and 20% O2 gas of the total pressure of 1000 atm by means of HIP techniques. Optimum combinations of Ts and Ta were determined for obtaining superconducting samples. Single-phase samples were obtained only for the composition La1.8Sr0.2CaCu2Oz for which the oxygen content, z, was determined to be 6.01±0.01 by coulometric titration. It was concluded that Ta was a crucially important factor for obtaining superconducting 326 phase with Tonc (approximately-greater-than) 40 K, that is, Ta (approximately-greater-than) 970 °C was required (for 6-h HIP annealing). It was demonstrated that a long HIP annealing was necessary to obtain a significant volume fraction for the superconducting 326 phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348560
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic properties of the Y1−xGdxCo3B2 system : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6540-6542 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic properties of Y1−xGdxCo3B2 with x=0, 0.2, 0.4, 0.6, 0.8, and 1.0 have been studied in a wide temperature range from 4.2 to 1250 K. All compounds studied here have the CeCo3B2-type structure which is a derivative of the RCo5 type one. In this system, the Co atom is nonmagnetic down to 4.2 K and the Curie temperature decreases almost linearly with increasing composition x and is expected to vanish at around x=0 (YCo3B2). For the sample with x=0.2, a spin-glass freezing point has been found in addition to the usual ferromagnetic Curie temperature. Gd magnetic moments obtained from the saturation magnetizations at T=4.2 K are generally smaller than those obtained from the Curie–Weiss constants in the high-temperature paramagnetic region, which suggests a slight polarization of the Co atoms antiparallel to the Gd moment in the ferromagnetic region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349900
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Critical current density and microstructure of YBa2Cu4O8 (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 384-389 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigated the intragranular critical current density Jc in YBa2Cu4O8 prepared by two routes with different oxygen pressures at various temperatures and applied fields. A relationship between the Jc's and the microstructures observed by transmission electron microscopy is discussed. The magnitude of Jc for the low oxygen processed sample is higher by a factor of 5 than that for the high oxygen pressure sample. Transmission electron microscopy reveals that the sample prepared at high oxygen pressure shows an almost perfect stacking sequence, but the low oxygen pressure prepared one has a severely distorted structure. We conclude that the difference in Jc(H) for the samples must be related to the different microstructures. Jc at a fixed magnetic field shows an exponential temperature dependence similar to that seen in other high-Tc superconductors. The field dependence is Jc∝H−n with n between 0.5 and 1.5, and with the n value becoming larger at higher temperatures. This type of the behavior may arise from the two-dimensional character of YBa2Cu4O8.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347726
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    Paper (German National Licenses)
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