Oxide high-temperature superconducting material, method of preparing same and superconducting wires

A method of producing a high-temperature oxide superconducting material, which comprises the steps of:

• a) preparing a mixture of materials corresponding to an oxide superconductor of the perovskite type structure comprising a first member selected from the group consisting of a yttrium compound, a lanthanoid compound, a thallium compound and a bismuth compound;
• at least one alkaline earth metal compound and a copper compound, and an alkali metal compound selected from the group consisting of a potassium compound, a sodium compound, a rubidium compound and a cesium compound in such an amount that the alkali metal compound is in the range of 0.01 to 10 mols;
• and
• b) heating the mixture to a temperature so as to convert the mixture into the superconductor of the perovskite type structure consisting essentially of the first member, the at least one alkaline earth metal and copper for a time sufficient to effect grain growth in the superconductor material, thereby to produce the superconductor containing the alkali metal in an amount not larger than 4 mole % based on the first member of the superconductor.