Compressive anneal processing (CAP) of Bi2223 superconducting tapes

The conventional processing of oxide powder-in-tube Bi2223 superconductor tapes involves iterative cycles of mechanical deformation to develop texture and reduce porosity, followed by thermal annealing to react components, relieve stress and heal cracks. However, texture and deformation hardening and cracking may limit the ability to obtain the desired grain texture through deformation alone. In addition, desintering of the oxide core occurs during annealing. We have developed a compressive anneal processing (CAP) technique in which a continuous uniaxial pressure is applied during the annealing. The new process is found to promote texture formation, enhance reaction kinetics and prevent desintering and bloating. Our initial results show that the CAP technique significantly improves the critical current density.