International Superconductivity Technology Center

Sumitomo Electric Industries, Limited

Matsushita Electric Industrial Co., Ltd.

Tohoku Electric Power Company, Inc.

International Superconductivity Technology Center, the Juridicial Foundation

Tohoku Electric Power Copany, Incorporated

International Superconductivity Technology Center, the Juridical Foundation

Ayako Yamamoto

Seiji Adachi

Makoto Itoh

Kazuyuki Isawa

Setsuko Tajima

Shoji Tanaka

Hisao Yamauchi

Wei-Zhi Hu

Lee Sergey Romonovich

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

A method of manufacturing an oxide superconductor, including the steps of mixing oxide materials of the metals contained in an oxide superconductor represented by HgBa.sub.2 Ca.sub.2 Cu.sub.3 O.sub.8+y to prepare a powder mixture of the composition noted above, molding the powder mixture to prepare a molded body of a desired shape, and applying a heat treatment to the molded body within a hermetic container at a temperature sufficient for bringing about a solid phase reaction of the oxide materials for at least 20 hours. Also provided is a method of manufacturing an oxide superconductor, including the steps of mixing at least one additive element selected from the group consisting of Pb, Bi, Tl, Au, Pt, Ag, Cd and In with oxide materials of the metals contained in a Hg-series 1223 type oxide superconductor to prepare a powder mixture, molding the powder mixture to prepare a molded body of a desired shape, and applying a heat treatment to the molded body within a hermetic container at a temperature sufficient for bringing about a solid phase reaction of the oxide materials for at least 10 hours.

Method of manufacturing oxide superconductor

Provided is an Hg--Ba--Ca--Cu--O oxide superconductor having a high superconductivity transition temperature Tc and a method which can prepare the same in excellent reproducibility. This oxide superconductor consists essentially of Hg, Ba, Ca, Cu and O, and is expressed in a chemical formula (Hg.sub.1-X Cu.sub.X)Ba.sub.2 Ca.sub.2 Cu.sub.3 O.sub.y, wherein X=0.05 to 0.7 and Y=8 to 8.75. A method of preparing the oxide superconductor comprises a step of mixing raw materials of Hg, Ba, Ca and Cu with each other so that (Hg+Ba):Ca:Cu =b:1:C and Hg:Ba=(1-a):a, wherein 0.625.ltoreq.a.ltoreq.0.714, 1.ltoreq.b.ltoreq.3 and 1.667.ltoreq.c.ltoreq.3.444, in mole ratio, and compression-molding the mixture, and a step of heat treating a compact obtained by the compression molding. This oxide superconductor has a superconductivity transition temperature Tc of 134 K, which is the highest at present.

(Hg Cu)Bg.sub.2 Ca.sub.2 Cu.sub.3 Oy oxide superconductor and method of

Provided is an Hg-Ba-Ca-Cu-O oxide superconductor having a high superconductivity transition temperature Tc and a method which can prepare the same in excellent reproducibility. This oxide superconductor consists essentially of Hg, Ba, Ca, Cu and O, and is expressed in a chemical formula (Hg.sub.1-X Cu.sub.X)Ba.sub.2 Ca.sub.2 Cu.sub.3 O.sub.Y, wherein X=0.05 to 0.7 and Y=8 to 8.75. A method of preparing the oxide superconductor comprises a step of mixing raw materials of Hg, Ba, Ca and Cu with each other so that (Hg+Ba):Ca:Cu=b:1:C and Hg:Ba=(1-a):a, wherein 0.625.ltoreq.a.ltoreq.0.714, 1.ltoreq.b.ltoreq.3 and 1.667.ltoreq.c.ltoreq.3.444, in mole ratio, and compression-molding the mixture, and a step of heat treating a compact obtained by the compression molding. This oxide superconductor has a superconductivity transition temperature Tc of 134 K., which is the highest at present.

(Hg,Cu)Ba.sub.2 Ca.sub.2 Cu.sub.3 O.sub.y oxide superconductor and

The oxide superconductor according to the present invention is represented by (Hg.sub.1-x Pb.sub.x)Ba.sub.2 Ca.sub.2 Cu.sub.3 O.sub..delta. (0.08.ltoreq.x.ltoreq.0.41, 7.625.ltoreq..delta..ltoreq.9.15), and has a crystal structure in which a lamination unit of (Hg, Pb)O.sub.z -BaO-CuO.sub.2 -Ca-CuO.sub.2 -Ca-CuO.sub.2 -BaO is laminated in a c-axial direction of the crystal structure (0.625.ltoreq.z.ltoreq.2.15). Further, the method of manufacturing an oxide superconductor, according to the present invention, includes the steps of: mixing material powders of HgO, PbO, BaO, CaO and CuO at a mole ratio of (Hg.sub.1-x Pb.sub.x):Ba:Ca:Cu=a:2:b:c (1.ltoreq.a.ltoreq.2.5, 2.ltoreq.b.ltoreq.3, 2.5.ltoreq.c.ltoreq.4) and compression-molding the mixture powder into a compact; and subjecting the compact to a thermal treatment at 600.degree.-750.degree. C.

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Tokyo, Japan

Ayako Yamamoto