IMPROVEMENT OF TRANSPORT CRITICAL-CURRENT DENSITY IN IN-SITU SYNTHESIZED SILVER-SHEATHED SUPERCONDUCTING TAPE OF TL0.78BI0.22SR1.6BA0.4CA2CU3O9-DELTA BY INTERMEDIATE ANNEALING AND PRESSING

Intermediate thermal annealing and static hydraulic pressing were applied to process in-situ synthesized silver-sheathed superconducting Tl0.78Bi0.22Sr1.6Ba0.4Ca2Cu3O9-delta tapes. It was found that this intermediate processing improved the tape performance as indicated by a 65% increase of transport critical current density (J(c)) at zero field and an even greater increase of 340% at 5.5 T. Scanning and transmission electron microscopy (SEM and TEM, respectively) and X-ray diffraction (XRD) were used to characterize the microstructural differences and phase formation of the tapes prepared by three different methods. It was found that a higher core density and more favorable pore distribution due to the intermediate processing were the main reasons for the improvement in J(c). Field-cooled (FC, B = 50 G) magnetization measurements using a Superconducting Quantum Interference Device (SQUID) demonstrated a better flux pinning for the tape subjected to the intermediate processing, which is consistent with the greater improvement of the transport J(c) at 5.5 T than at zero field.