THE FORMATION MECHANISM AND THE DEVELOPMENT OF GRAIN TEXTURE IN THE PREPARATION OF AG-SHEATHED BI-2223 SUPERCONDUCTING TAPES

The mechanism and development of cold-working and grain-growth texture of Bi-2212 and the corresponding inheritance of texture by Bi-2223 in Ag-sheathed tapes has been investigated. Precursor powder in the Ag t ube was found to flow, rotate and fracture along the crystallites. Thi s together with sliding among crystallites forms the basis of the defo rmation process in Bi-2212 texturing during the cold-working process. Bi-2212 was formed via a rapid melting process, yielding a strong epit axial melt-textured microstructure from a subsequent heat treatment Bi -2223 was found to form on Bi-2212, with the Bi-2223 texture being inh erited from the Bi-2212 texture. This is best explained by an intercal ation mechanism for Bi-2223 phase formation.