Improved uniformity of microstructure and electrical properties of Bi-2223/Ag superconducting tapes

A special mechanical deformation technique, 'sandwich' rolling (SR), togeth er with the conventional rolling technique, normal rolling (NR), was used t o intermediately deform Bi-2223/Ag superconducting tapes. The tapes process ed by these two techniques were compared in terms of phase composition, mic rostructure, critical temperature (T,) and critical current density (J(c)). It was found that while there was no difference in phase composition betwe en the two types of tapes, density, degree of grain alignment and J(c) were considerably higher in the SR tapes than in the NR tapes. In particular, t he uniformity of microstructure, T-c, and J(c) between the filaments across the width of the tapes were significantly improved by the SR compared to t he NR technique. The results show that in terms of mechanical effects on Bi -2223/Ag tapes SR is more like uniaxial pressing, rather than conventional rolling. (C) 2001 Elsevier Science B.V. All rights reserved.