Abstract: 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 Bi2Sr2Ca2Cu3Oz, or (Bi, Pb) 2Sr2Ca2Cu3Oz, 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.

Abstract: Methods for implementing production of an oxide superconductor joined member, excellent in electric current transmission performance, without a need of going through particularly complex steps, are provided. When joining together oxide superconductors by use of a solder composed of an oxide superconducting material, a finally solidified portion of the solder is positioned in a region where a transmission path of electric current flowing between oxide superconductor base materials as joined together is not obstructed by, for example, disposing the solder on a face of the oxide superconductor base materials, other than butting surfaces of the oxide superconductor base materials, so as to straddle both the base materials like bridge-building. Current flow is also not obstructed by, for example, shaping junction faces of the oxide superconductor base materials such that at least portions of the butting surfaces thereof are in the shape of sloped open faces, parting from each other.

Abstract: There is provided a method for preparing a large and perfect oxide crystal useful for oxide superconductors and laser transmitting elements. In the present method for preparing a large oxide single crystalline material such as superconductive crystals of RE123, a crystal precursor material is supercooled prior to the solidification thereof in the course of crystal growth of the oxide by a supercooling solidification process, followed by subjecting said precursor material to continuous slow heating while keeping the supercooled condition to promote crystal growth, as shown in FIG. 7. Seed crystals may be added to the crystal precursor material prior to solidification, if necessary, as also shown in FIG. 7.

Abstract: There is provided RE-Ba-Cu-O oxide bulk superconductors in which considerably high critical current density is obtained at relatively high temperature. In the present RE-Ba-Cu-O bulk superconductors, RE is a combination of two or more elements selected from La, Nd, Sm, Eu and Gd, at least one of them being La, Nd and Sm and the remainder being Eu or Gd, in which a parent phase thereof comprises a RE.sub.1+x Ba.sub.2-x Cu.sub.3 O.sub.y crystal wherein -0.1<x<0.2 and 6.7<y<7.1, and 5 to 50% by volume of a RE.sub.2 Ba.sub.2 CuO.sub.5 fine dispersed phase having partide size of 0.01 to 0.5 .mu.m. Preferably, a total amount of Eu and Gd in the RE site is 40% by weight or less, while a slight amount of Pt may be added. As a result, the critical current density at liquid nitrogen temperature can be improved to 10,000 A/cm.sup.2 or more under a condition where a magnetic field of 3T is impressed parallel to c axis of the crystal.

Abstract: There is provided a method for stably preparing rare earth (RE) 123 type oxide superconductors exhibiting outstanding superconductive properties in the atmosphere. In the method for preparing RE 123-type oxide superconductors by melting, cooling and solidifying a starting composition containing one or more than two kinds of RE such as Y, Sm, Nd, etc., and Ba, Cu and O as constituent elements to crystallize the RE 123-type oxide superconductors, the quantity of replacement between RE and Ba in "RE 123 crystals to be formed" is controlled by changing the initial constitution of the starting composition, for example, by changing the initial constitution to a more Ba-rich side than a composition on a 123-211 (or 422) tie line on a phase diagram to yield RE 123-type oxide superconductors in the atmosphere, which exhibits a critical temperature of 90 K or above and higher critical current density (Jc) in a magnetic field. A trace amount of Pt or CeO.sub.