Flux pinning of Bi2Sr2CaCu2O8+δ/Ag superconductors utilizing (Sr,Ca)14Cu24O41 defects and nanophase Al2O3 and Au particles

Investigations into flux-pinning of Bi2Sr2CaCu2O8+delta/Ag (Bi-2212/Ag) thick film conductors utilizing micron-sized (Sr,Ca)(14)Cu24O41 and nanophase Al2O3 and Au particles are described. Addition of defect particles delayed and reduced formation of 2212 c-axis texture, while improving film quality by inhibiting Sr:Ca:Cu:O defect formation. Oxide defects were observed to rapidly coarsen in the melt simultaneously with beneficial increase of 2212 texture. Nanophase Al2O3, reacted rapidly (< 4 min) with 2212-type melts (Sr:Ca = 1.33-2.07) to form solid-solution (Sr,Ca)(3)Al2O6 with Sr:Ca ratio close to the Sr:Ca composition of the precursor matrix. Addition of nanophase Al2O3 improved the J(c) (1 T) over the range 20-30 K, e.g. J(c) (30 K, 1 T)/J(c) (5 K, 0 T) = (< 0.001), 0.005, and 0.065 for 0%, 10% and 46% molar addition, respectively. The addition of nanophase or micron-sized Au completely suppressed 2212 c-axis orientation for the processing temperatures tested. (C) 2000 Elsevier Science B.V. All rights reserved.