Abstract: The hole density of an oxide superconductor having holes as carriers is higher than the hole density to bring the highest value of the superconductivity critical temperature Tc thereof, and it can be made higher than the optimal density to bring the highest Tc value by treating the oxide superconductor with heat in an oxidizing gas atmosphere, or by replacing positive ions constituting the oxide superconductor except for copper with ions of a low valence number. Accordingly, it is possible to substantially reduce the rate of decrease of the critical current density owing to an applied magnetic field when the magnetic field is applied parallel to the crystal c axis, and to allow a current conductor produced by using the oxide superconductor to have high critical current density.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.