| 摘要 |
There is disclosed an improved process for preparing a superconducting composition having the formula MBa2Cu3Ox wherein M is selected from the group consisting of Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu; x is from about 6.5 to about 7.0; said composition having a superconducting transition temperature of about 90 K; said process consisting essentially of heating a precursor powder in an oxygen-containing atmosphere at a temperature from about 875 DEG C to about 950 DEG C for a time sufficient to form MBa2Cu3Oy, where y is from about 6.0 to about 6.4; and maintaining the MBa2Cu3Oy in an oxygen-containing atmosphere while cooling for a time sufficient to obtain the desired product; said precursor powder being prepared by (a) mixing M2O3, Ba(OH)2.8H2O and CuO powders in an atomic ratio of M:Ba:Cu of about 1:2:3, or (b) forming an aqueous solution of M(NO3)3, Ba(NO3)2 and Cu(NO3)2 in an atomic ratio of M:Ba:Cu of about 1:2:3, adding to the resulting solution sufficient citric acid monohydrate to convert the metals present to their corresponding citrates, and spray drying the resulting solution to obtain the precursor powder. |
