| 摘要 |
There is disxlosed a process for preparing a novel superconducting material. This material has the formula YBa2Cu3O7-x wherin x is equal to or less than 0.3, the material has a bulk density of from about 90 to about 96 percent, and the hardness of the material is in excess of 5.0 GigaPascals. In the first step of the process, there is provided a pure powder comprised of barium, yttrium, and copper in a mole ratio of 2/1/3. Such powder is comprised of less than 1.0 mole percent of impurity. In the second step of the process, the powder is compacted. Thereafter, the compacted powder is fired at a temperature of from about 1,000 to about 1,300 degrees Clesius for a period not exceeding 12 hours. In the third step of the process, the temperature of the fired powder is reduced at least 20 degrees Celsius to a first reduced temperature within the range of from about 960 to about 990 degrees Celsius, and the powder is than held within this reduced temperature range for at least 1 hour. In the fourth step of the process, the powder is cooled to a second reduced temperature within the range of from about 400 to about 700 degrees Celsius, and the powder is then held within the second reduced temperature range for from about 1 to about 24 hours. During the firing and heat-treating steps, an oxygen-containing gas is flowed over the compacted powder at a flow rate of from about 0.25 to about 2.0 liters per minute.
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