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 microstruc ture and critical current density, J(c), of Ag-Sheathed Bi-2223 tapes were investigated. The calcined powder with a nominal composition of B i1.89Pb0.41Sr2.01Ca2.23Cu3.03Oy was milled for various times using a p lanetary ball mill. The transport property of the tapes was found to d epend strongly on the particle size of the precursor powder. Enhanced reactivity of the milled powder facilitated the formation of 2223 phas e and resulted in an increase of J(c). Excessive milling, however, led to the amorphization of the powder. The heavily deformed powder was d ecomposed into 2201 and second phases during degassing treatment, whic h retarded the transformation of 2223 phase and hence significantly de graded the electrical property of the tapes. (C) 1998 Elsevier Science B.V.