Currently, powder-in-tube Bi-2223 superconductor is the most promising candidate for fabricating long-length conductors. Intensive investigations have shown that the critical current density of fully processed tapes is affected by a large variety of processing parameters. Among these are the thermomechanical processing schedule and the extent of Bi-2223 phase conversion. In this study, a powder precursor was prepared using an aerosol pyrolysis technique, which has been shown to have the advantage of reduced processing time. Powder-in-tube conductors were fabricated using the aerosol precursor powder, and the thermomechanical processing steps were varied. Different schedules were correlated with the amount of Bi-2223 phase as well as the critical current density. The number of pressings and the length of sintering time between pressings were found to be closely related to the critical current density at various stages of the thermomechanical treatment.
Powder-in-tube Bi-2223 is currently the most promising high-temperature superconductor that can be fabricated in long lengths by industrial processes, and is likely to be used as the conductor component in first-generation applications. Intensive investigations of these conductors have revealed that the critical current density of fully processed tapes is influenced by a large number of processing parameters. Among these are the thermomechanical processing schedule and the extent of Bi-2223 phase conversion. These parameters are, in turn, affected by the precursor stoichiometry. In this study, powder precursors with varying Cu content were prepared using an aerosol pyrolysis technique, and powder-in-tube conductors were fabricated using these precursors. Both fast and slow cooling rates were employed during thermomechanical processing, and different treatment schedules are correlated to the critical current density. The results indicate that the effect of excess Cu on is minor compared to the large enhancements obtained by employing one or more slow-cooling steps in the thermomechanical processing schedule.
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