Optimal composition and intergranular contact in thallium containing superconducting tapes

The structures and properties of Y‐based, Bi‐based, and Tl‐based CuO superconductors are compared. In the Tl2Ba2Ca2Cu3O10, TlBa2Ca2Cu3O8.5, and TlBa2CaCu2O6.5 types of superconductors, flux‐pinning is stronger when the thickness of the insulating layer is decreased as expected from 2‐dimensional model of interacting superconducting layers. The transport Jc is limited by weak links which can be strengthened by various types of granular reorientation processes such as melt‐texturing and compressive deformation. The data on a 24‐meter uniform and flexible tape of silver‐sheathed Tl0.5Pb0.5Ba0.4Sr1.6Ca2Cu3O8.25 are presented.