The effect of core density on the formation of the 2223 phase in (Pb/Bi)(2)Sr2Ca2Cu3Ox superconducting tapes

The effect of core density on the processing of superconducting tapes has been investigated. Tapes were prepared with different 'as-rolled' densities, but all other mechanical and thermal parameters remained the same. The precursor powder used had a nominal stoichiometry of Bi1.84Pb0.34Sr1.91Ca2.03Cu3.06Ox, doped with 15% Ag by weight prepared by Merck Ltd. The 'as-rolled' tapes had Vickers' microhardness numbers, H-v, of 90 and 180 kg mm(-2). The local 2223 phase formation across the thickness of the core was studied in tapes of these core densities by sintering them at 818 degrees C for various times In an atmosphere of 7.5% O-2. XRD analysis revealed that low density tapes formed the 2223 phase considerably faster than high density tapes. For example, after 10 h of sintering, the low and high density tapes had a 45% and 3% 2223 phase content at the centre of the core, respectively. (C) 1997 Published by Elsevier Science Ltd.