A 2-POWDER PROCESS FOR BI-2223 PRECURSORS

A two-powder process is described for the production of uniform, fine- grained Bi2Sr2Ca2Cu3Oy (Bi-2223) powders. One powder is the Bi2.1-xPbx Sr1.9-yCayOz (2:2 Cu-free) phase. The other is a multi-phase powder of approximate overall composition SrCaCu3Oy. The 2:2 Cu-free is one of the first Bi-containing phases to form from a nominal Bi-2223 mixture of oxides and carbonates. This precursor route was chosen for investig ation because (1) the powders have very similar particle morphologies and (2) the mixing volumes are closely matched. Both of these characte ristics facilitate the milling and blending process. This precursor mi x was found to be stable in that explosive grain growth of undesirable phases was not observed during sintering. Critical current densities up to 26,900 A/cm(2) in self field at 75 K were obtained in tapes.