Many studies have shown that the phase assemblage of starting powders influences
the phase evolution of the 2223 phase;
but it is quite difficult to control the phase balance in
precursor powders using a singlepowder process. In this study, (Bi,Pb)2212 and CaCuO2 are
formed as separate intermediate phases, then mixed and processed together within a silver
sheath. The
phase transformation kinetics, microstructure and transport properties of the
resulting tapes are strongly dependence on the phase content of the precursor powders. Nearly
pure 2223 can been produced when sintering for as little as 40 h, using (Bi, Pb)2212 and
CaCuO2 presursors, and the fraction of nonsuperconducting phases seem to become minimum
at the boundary of the oxide core. The effects of mechanical deformation and heat treatment
cycles on silvercore interfaces and critical current densities in 37,61 and 85 filament tapes
have been studied for the tapes fabricated using the
twopowder process. A smooth Agoxide
interface has been obtained through accurate control of the pass reduction ratios. This
experiment demonstrates that the existence of large platelike 2212 grains in the presursors can
accelerate the diffusion of Ca, Cu during sintering stage and increase the degree of texture of
2223 grains.Tapes with a thickness of 024 mm can be made using flat rolling without any
sausaging effect. Jc values of 30104 A/cm2(Ic=53 A) and 17104 A/cm2(Ic=35 A) at 77 K and self
field are achieved for rolled short samples and tapes 20 m long, respectively.