The grain alignment of Bi2223, Bi2212 and Bi2223+Bi2212 phases in mechanical deformation and annealing processes

It is believed that the grain alignment of oxide superconductors plays an important role in improving the critical current density, Although mechanical deformation and thermal treatment are widely used to produce grain alignment in the BSCCO system, the alignment mechanisms have not been well understood. The present work studies the grain alignment behaviours of Bi2223, Bi2212 and Bi2223 + Bi2212 compounds by using X-ray diffraction. Results indicate that the effects of mechanical deformation on the grain alignment of Bi2212 and Bi2223 phases during the fabricating process of Bi2223 superconductors are quite different. Heavy deformation produces a high degree of grain alignment for Bi2212 in the early stage of Bi2223 fabrication but not for the Bi2223 phase in the later processing stages. The subsequent annealing clearly improves the grain alignment for Bi2223, Bi2212 and Bi2223 + Bi2212. Based on these experimental results, optimal mechanical-thermal processes were suggested for BSCCO superconductor fabrication. (C) 1997 Elsevier Science B.V.