Abstract: This invention relates to an oxide superconducting wire comprising (1) oxide superconducting filaments, (2) a high-density ceramic layer uniformly surrounding each of the filaments, and (3) a silver sheath that directly covers the ceramic layer. The ceramic layer becomes non-superconducting when the filaments are cooled to an operating temperature of oxide superconductors. The oxide superconductors can be isolated by the ceramic that acts as a highly resistive material or an insulator. A high normal resistance is achieved, and thereby AC loss is reduced remarkably.

Abstract: The diameter of a first metal tube charged with raw material powder is reduced for obtaining an elementary wire. A plurality of such elementary wires are charged into a second metal tube, which in turn is reduced in diameter for obtaining a round first wire having a plurality of first filaments. The first wire is uniaxially compressed thereby obtaining a tape-like second wire having a plurality of second filaments. The second wire is heat treated thereby obtaining an oxide superconducting wire including a plurality of superconductor filaments. The maximum grain size of the raw material powder is smaller than the minor diameter of the first or second filaments.

Abstract: An Nb.sub.3 Al multi-filamentary superconducting wire capable of realizing both stabilization of a superconducting state and increase in capacity is provided. The Nb.sub.3 Al multi-filamentary superconducting wire includes a core formed of copper or copper alloy and located at the center of the wire; a multi-filamentary superconductor layer located around the core and having filaments containing Nb and Al as constituent elements embedded in a matrix formed of copper or copper alloy; and a high resistance layer located around the multi-filamentary superconductor layer, and is characterized in that a sectional area of the core is at least 15% of the total sectional area of the core and the matrix and that the core and the matrix are formed of copper or copper alloy of at least 99.9% purity.

Abstract: The method of preparing an NB.sub.3 Al superconducting wire comprises the steps of passing an Nb/Al composite wire consisting of an Nb metal or an Nb alloy and an Al metal or an Al alloy through a furnace for heating the same from the room temperature to a prescribed temperature, subsequently passing the same through the furnace for holding the same at the prescribed temperature, and subsequently passing the same through a cooling part for cooling the same from the prescribed temperature to the room temperature, and these steps are continuously carried out by continuously moving the wire. According to the present invention, it is possible to obtain an Nb.sub.3 Al superconducting wire having homogeneous characteristics along its overall width with a high critical current density.

Abstract: Disclosed herein is a wire for an Nb.sub.3 X superconducting wire, which is improved in workability and soundness of a diffusion barrier layer without increasing the diffusion barrier layer in thickness. This wire for an Nb.sub.3 X superconducting wire comprises a wire which is prepared by superposing and winding up a first sheet consisting of pure Nb or an Nb alloy and a second sheet consisting of metal atoms X, reacting with Nb for forming a compound exhibiting superconductivity, or an X alloy, a stabilizing material layer which is provided to enclose the wire, and a diffusion barrier layer which is provided between an outer surface of the wire and an inner surface of the stabilizing material layer for preventing the metal atoms X from being diffused in the stabilizing material layer, and the diffusion barrier layer is made of a metal material having larger tensile strength than that of the first sheet. It is possible to obtain a high-performance Nb.sub.