【摘要】 较详细地研究了银包套Bi（2223）带材在低温强磁场下的传输临界电流密度（J_c）特性,实验结果表明,Bi（2223）带材在一定的磁场下J_c随温度的变化有两个不同的区域,在低于某一温度T_cm（H）后,J_c（T）由零开始按J_c∞（I-T/T_cm）^?指数形式增加;而温度远低于T_cm后,J_c（T）则随温度的降低线性增加,J_c（T）的线性关系可由传统磁通蠕动理论理解,而在T_cm附近的J_c（T）指数变化机制仍不清楚,本文采用点阵熔化概念和磁场引起的颗粒超导电性对这一结果进行了很好的解释,并进一步推论出,Bi（2223）带材之所以能获得较高的J_c是由于其晶粒间的连接形成Josephson邻近效应结的结果,在一定温度以下,这些结可能形成强耦合甚至转变成邻近效应超导体.更多还原

【Abstract】 Transport critical current density Jc of a silver-sheathed Bi-2223 tape was studied at low temperature and high magnetic field ranges. It was found that for a fixed field JC(T) contains two different parts: Jc(T) first increased exponentially from zero in a form of Jcoc(l - T/Tcm)n after temperature was reduced to a value of Tcm and then at temperatures well below Tcm Jc(T) dependence becomes linear. This linear Jc(T) nature may be interpreted from conventional flux creep theory. However, mechanism of nonlinear Jc(T) dependence near Tcm is still not clear. In this paper, we offer an explanation of this effect by using the concept of flux lattice melting and field-induced granularity. It is concluded that the field-induced Josephson junctions are dominated by SNS proximity-effect junctions. At low temperatures, this type of junctions may be well coupled or even become proximity-effect superconductor, which may be a reason why silver-sheathed Bi-system tapes have higher Jc values.更多还原