Directional crystallization of the 2223 phase prepared by melt-quench methods

Three superconducting phases in the Bi-Sr-Ca-Cu-O system have been discovered. In this investigation, emphasis was placed on optimizing conditions for the directional growth of the high Tc phase (2223, with a Tc ∼ 107K). A systematic study of factors favorable for the promotion of the high Tc phase (e.g., starting composition, chemical modification, heat-treatment, etc.) was carried out. Small amounts of Pb and Sb additives, coupled with heat-treatment in reduced oxygen atmospheres, resulted in a significant improvement in properties. Development of the high Tc phase will be discussed with respect to XRD, SEM, TEM, SQUID, and resistivity data. The use of thermal gradients (stationary and moving zones) as well as mechanical methods (rolling, swaging) will be discussed in the context of grain alignment and critical current densities