Optimization of tape width and powder packing density in the powder-in-tube processing of (Bi,Pb)-2223 tapes

The influence of starting packing density (SPD) and tape width on the final core density and J(c)of PIT processed (Bi,Pb)-2223/Ag tapes was studied. T welve sets of tapes with varying SPD (2.3 to 3.3 g cm(-3)) and wire diamete r prior to flat rolling (1 to 3 mm) were fabricated using silver tubes of O D 10.0 mm and ID 7.5 mm keeping the other parameters identical. The highly packed samples (SPD 3.3 g cm(-3), i.e., powder fraction 40 wt.%) yielded pu nctured tapes with significantly low values of core density (84-89% of rho( th)) and J(c)(4.6-10.5 kA cm(-2)). SPD in the range 2.3-2.8 g cm(-3) (i.e., powder fraction 27-33.5 wt.%) yielded good quality tapes with core density varying from 92.5-97% of rho(th) and J(c) from 8.1 to 18.7 kA cm(-2) depen ding on their width. Best results were obtained for tapes with SPD around 2 .8 g cm(-3) and width around 4.2 mm corresponding to a wire diameter of 2 m m. Possible reasons for the observed variations of core density and J(c) ar e explained. (C) 1998 Elsevier Science B.V. All rights reserved.