| 摘要 |
PURPOSE:To prevent the generation of crack caused by the absorption of excess oxygen and thermal strain and to improve the critical current density of a superconductor by heat-treating a formed article of a Bi-based oxide superconducting substance (precursor) and cooling or heat-treating the product under specific condition. CONSTITUTION:A formed article of a Bi-based oxide superconductor composed of Bi, an alkaline-earth metal, Cu and 0 or its precursor substance is sintered within a temperature range between TM-20 deg.C and TM+40 deg.C (TM is melt-initiation temperature), i.e. 890-950 deg.C to form a superconducting phase and obtain a heated material. The heated material is cooled from 700 deg.C to 200 deg.C at a cooling rate of >=10 deg.C/min in an atmosphere having an oxygen partial pressure of >=0.1atm or cooled from 700 deg.C at a cooling rate of <10 deg.C/min in an atmosphere having an oxygen partial pressure of <0.1atm to effect the absorption of oxygen and, as necessary, the cooled product is heat-treated at 700-200 deg.C in an atmosphere having an oxygen partial pressure of <0.1atm to remove the oxygen absorbed in excess. |
