| 摘要 |
There is disclosed an improved process for preparing a superconducting composition having the formula MwAzCuvOx, wherein M is selected from the group consisting of Bi, Tl, Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu; A is at least one alkaline earth metal selected from the group consisting of Ba, Ca and Sr; x is at least 6; w is at least 1; z is at least 2 and v is at least 1; said composition having a superconducting transition temperature of above 77 K, preferably above about 90 K; said process consisting essentially of (a) forming a suspension having an M:A:Cu atomic ratio of w:z:v by mixing A(OH)2, AO or AO2 and M2O3 with an aqueous solution of cupric carboxylate or cupric nitrate at a temperature from about 50 DEG C to about 100 DEG C, or mixing A(OH)2 with an aqueous solution of Cu carboxylate, nitrate or a mixture thereof and M carboxylate, nitrate or a mixture thereof at a temperature from about 50 DEG C to about 100 DEG C; (b) drying the suspension formed in step (a) to obtain a precursor powder; and (c) heating and cooling the powder under specified conditions to form the desired superconducting composition. Shaped articles thereof are also disclosed. |
