Mechanical grinding of precursor powder and its effect on the microstructure and critical current density of Ag/Bi-2223 tapes

The effects of the particle size of precursor powder on the microstructure and critical current density, J(c), of Ag-Sheathed Bi-2223 tapes were investigated. The calcined powder with a nominal composition of Bi1.89Pb0.41Sr2.01Ca2.23Cu3.03Oy was milled for various times using a planetary ball mill. The transport property of the tapes was found to depend strongly on the particle size of the precursor powder. Enhanced reactivity of the milled powder facilitated the formation of 2223 phase and resulted in an increase of J(c). Excessive milling, however, led to the amorphization of the powder. The heavily deformed powder was decomposed into 2201 and second phases during degassing treatment, which retarded the transformation of 2223 phase and hence significantly degraded the electrical property of the tapes. (C) 1998 Elsevier Science B.V.