Fabrication of Ag/Bi2Sr2Ca1Cu2O8 +/- 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-sheathe d Bi2Sr2Ca1Cu2O8+/-x (2212) superconducting tapes. Intimately mixed Bi2O3-S r-Ca-Cu-bearing powder was first synthesized by a two-stage, high-energy/lo w-energy mechanical alloying process. The powder was then packed into silve r 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 h eat treatment at 350-860 degrees C in oxygen. Subsequent annealing at 897 d egrees C, followed by slow cooling and subsolidus annealing at 850 degrees C, yielded 2212 grains with enhanced c-axis alignment. The resulting tapes exhibited average and maximum transport J(c) (4.2 K, self-field) values of 3.2 x 10(4) and 6.8 x 10(4) A/cm(2), respectively.