DEVELOPMENT OF MICROSTRUCTURE AND SUPERCONDUCTIVITY OF SILVER-CLAD BI(2223) COMPOSITE TAPES IN THE PROCESS OF HEAT-TREATMENT

A systematic study on the development of phase composition, microstructure and superconducting properties (critical temperature T-c and critical current density J(c)) in silver-clad (Bi,Pb)(2)Sr2Ca2Cu3O10 composite tapes during the process of heat treatment has been conducted using X-ray diffraction, scanning electron microscopy and electrical measurements. The correlation between the tape's high T-c phase purity, microstructure and superconducting properties at different heat treatment stages has been carefully analysed and explained. The results indicate that pure high T-c phase, high degree of grain alignment, high mass density and good connection between grains are all essential for superconducting tapes to carry a large current. With the optimized process parameters, a critical current density J(c) up to 32 665 A cm(-2) (corresponding critical current, 42.3 A) at 77 K and self-magnetic field for silver-clad (Bi,Pb)(2)Sr2Ca2Cu3O10 superconducting composite tapes has been achieved.