Growth of the Bi-2223 phase after a short nucleation stage at high temperature

A new two-step annealing procedure is investigated in order to accelerate t he kinetics of transformation and reaction: a short stage at high temperatu re (870 degreesC), to induce nucleation of the high-transition temperature phase "2223", is followed by a second stage at lower temperature (830 degre esC) to promote its growth. Magnetic susceptibility measurements on fibres submitted to this heat treatment cycle show a transition onset to supercond uctivity state at temperatures higher than that observed for samples anneal ed without nucleation stage. The increase of T-c values are due to the earl y development of the "2223" phase. Electrical resistance measurements corro borate that this new two-step procedure is an alternative process to develo p the "2223" phase without the detrimental effect of liquid-phase formation . (C) 2001 Elsevier Science B.V. All rights reserved.