International Superconductivity Technology Center

Other

International Superconductivity Technology Center, the Juridicial Foundation

International Superconductivity Technology Center, the Juridical Foundation

Setsuko Tajima

Ayako Yamamoto

Wei-Zhi Hu

Lee Sergey Romonovich

Sergey Lee

Sergey Romanovich Lee

The invention is intended to establish means for manufacturing MB single crystals and to provide a useful superconductive material (wire rod and so forth) taking advantage of anisotropic superconductive properties thereof. A mixed raw material of Mg and B or a precursor containing MgB crystallites, obtained by causing reaction of the mixed raw material of Mg and B, kept in contact with hexagonal boron nitride (hBN), is held at a high temperature in the range of 1300 to 1700&deg; C. and under a high pressure in the range of 3 to 6 GPa to cause reaction for forming an intermediate product, thereby growing the MB single crystals having anisotropic superconductive properties via the intermediate product. The single crystals have features such that, depending on a direction in which a magnetic field is applied thereto, an irreversible magnetic field strength becomes equivalent to not less than 95% of a second magnetic field strength, so that adjustment of crystal orientation thereof results in production of a superconductive material excellent in property. Further, it is useful in effecting growth of the single crystals to cause a reducing agent such as Mg and so forth to coexist at the time of the reaction, or to provide a temperature gradient in melt occurring in the course of the reaction.

Mgb2 single crystal and its production method, and superconductive material containing mgb2 single crystal

An Hg- or Nd-based oxide superconductor comprises Ba as a constituent element and has a content of carbon as an impurity at a level of not greater than 2.0 atomic % whereby the oxide superconductor stably shows high superconducting characteristics without causing degradation with time. For its production, BaO, which has a reduced content of carbon impurity of 0.5% or below, is provided as a feed stock for Ba, and the starting materials are mixed and processed in a dry atmosphere wherein an amount of a carbon-containing gas is suppressed to a certain level, thereby obtaining the oxide superconductor.

Oxide superconductor and method for producing same

The invention provides a method for stably preparing a bismuth-based high temperature superconductor of a Bi-2223 single-phase or a Bi/Pb-2223 single phase, wherein a second phase is not allowed to reside, at a low cost and efficiently. With the method described above, mixed powders of raw materials (mixed powders of oxides and carbonates), obtained by mixing the raw materials such that a mixing ratio of constituents, Bi:Sr:Ca:Cu or (Bi, Pb):Sr:Ca:Cu, becomes identical to the stoichiometric ratio of a crystal of the superconductor Bi Sr Ca Cu O , or (Bi, Pb) Sr Ca Cu O , respectively, are used as raw material for sintering, and the sintering is applied thereto, using KCl as a flux. In this case, the raw material for the sintering as calcinated is preferably used, and the sintering is preferably applied at a sintering temperature kept at a constant level.

Method for preparing bismuth-based high temperature superconductors

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Tokyo, Japan

Setsuko Tajima