| 简介 |
Described is a superconducting composition comprising a metal oxide of the formulaT d M* e Cu f O g wherein "T" is a trivalent transition metal such as Bi, Tl, In, Sb, or mixtures thereof; "M*" is a mixture of alkaline earth metals such as Sr and Ca, Sr and Mg, and Ca and Mg in ratio of the alkaline earth metal of larger atomic radius (M L) to the alkaline earth metal of smaller atomic radius (M S) of from about 1 : 1 to about 3 : 1; "d" is a number from about 1 to about 3; "e" is a number from about 1 to about 6; "f" is a number from about 1 to about 6; "g" is a number between from about (3d + 2e + 2f)/2 to about (3d + 2e + 3f)/2 that provides the metal oxide with zero electrical resistance at a temperature of 77°K or higher. Preferably "T" is bismuth; "M*" is Ca and Sr at ratio of 1 : 2; "d" is 2; "e" is 3; "f" is 2 and "g" is a number between about 8 to about 9 which provides said composition with zero electrical resistance at a temperature of 77°K or higher. |
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