Fabrication of Ag/Bi{sub 2}Sr{sub 2}Ca{sub 1}Cu{sub 2}O{sub 8{+-}}{sub x} superconducting tapes by the oxidation and postoxidation (partial melt) annealing of malleable, metal-bearing precursors

A solid metal-bearing precursor route has been used to fabricate Ag-sheathed Bi{sub 2}Sr{sub 2}Ca{sub 1}Cu{sub 2}O{sub 8{+-}}{sub x}(2212) superconducting tapes. Intimately mixed Bi{sub 2}O{sub 3}-Sr-Ca-Cu-bearing powder was first synthesized by a two-stage, high-energy/low-energy mechanical alloying process. The powder was then packed into silver tubes and formed into tapes by drawing and biaxial (Turk's-head) rolling. The precursor tapes were oxidized and converted into Ag-sheathed 2212 by heat treatment at 350-860 degree sign C in oxygen. Subsequent annealing at 897 degree sign C, followed by slow cooling and subsolidus annealing at 850 degree sign C, yielded 2212 grains with enhanced c-axis alignment. The resulting tapes exhibited average and maximum transport J{sub c} (4.2 K, self-field) values of 3.2x10{sup 4} and 6.8x10{sup 4} A/cm{sup 2}, respectively. (c) 2000 Materials Research Society.