Transport and magnetisation measurements of Tl-1223 tapes-thenature of current paths and the role of grain boundaries at highmagnetic fields

摘要

The key factors that make the thallium-based 1223 phase conductors attractive candidates for high field applications are a high transition temperature (~ 115 K), and an irreversibility line comparable to YBa2Cu3O7. However, a third important factor is the grain boundary behaviour. We have made detailed transport current-voltage (I-V) and magnetic studies of a Ag-0.1%Hf sheathed Tl-1223 tape. For low fields (B<100 mT) its critical current density Jc performance displays the “weak-link” signatures well-known for polycrystalline YBa2Cu3O 7. At high fields however (B>100 mT) there is a plateau region in its Jc(B) characteristics. Possible scenarios for inter-granular transport current conduction and dissipation in this region are discussed