Magnetic Field Dependence of Jc in A T1-1223 Wire; Presence of Pinning and Good Grain Boundary Connectivity.

The existence of effective pinning in single T1-layer 1223 superconductors has been reported [1-3], as opposed to lower values in T1- and Bi-double layer systems, which is intimately related to their crystal structures. In order to investigate the possibility of T1-1223 being applied as a practical superconductor, tape shaped wires of the chemical composition (T10.5Pb0.51 (Sr0.8Ba0.2Ca2Cu3O9were prepared. Transport Jc of T1-1223 was measured to be 1.8 x 104 A/cm2 at 77K in the absence of a magnetic field. These results seem to imply that T1-1223 has, not only effective pinning because of having a more 3-dimensional vortex line lattice like YBa2Cu3O7, but also better grain boundary weak-link performance than YBa2Cu3O7. PresenT1y it appears that T1-1223 may be a superior choice to make better superconducting wire, because of these considerations and of the higher Tc of 120K. p](T10.5Pb0.5)1Sr2CaCu2O7 (T1-1212) also seems to have effective pinning, as well as T1-1223, supporting the idea that shorter Cu-O plane spacing, or absence of thicker insulating region such as T12O2 or Bi2O2 double layer, are beneficial for effective pinning through facilitating a better 3D-like vortex line lattice [4,5]. Our “1212” and “1223” samples are good counter examples to the 2D pancake-like vortex theory [6,7].