Fabrication of Ag/Bi2Sr2Ca1Cu2O8±x superconducting tapes by the oxidation and postoxidation (partial melt) annealing of malleable, metal-bearing precursors

Abstract

A solid metal-bearing precursor route has been used to fabricate Ag-sheathed Bi2Sr2Ca1Cu2O8±x (2212) superconducting tapes. Intimately mixed Bi2O3–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 °C in oxygen. Subsequent annealing at 897 °C, followed by slow cooling and subsolidus annealing at 850 °C, yielded 2212 grains with enhanced c-axis alignment. The resulting tapes exhibited average and maximum transport Jc (4.2 K, self-field) values of 3.2 × 104 and 6.8 × 104 A/cm2, respectively.