Ž . Physica C 335 2000 129–133 www.elsevier.nlrlocaterphysc Flux pinning of Bi Sr CaCu O rAg superconductors utilizing 2 2 2 8qd ž / Sr,Ca Cu O defects and nanophase Al O and Au particles 14 24 41 2 3 T. Haugan a, ) , W. Wong-Ng a , L.P. Cook a , H.J. Brown a , L. Swartzendruber a , D.T. Shaw b a Materials Science and Engineering Laboratory, National Institute of Standards and Technology, 100 Bureau Dr. Stop 8520, Gaithersburg, MD 20899-8520, USA b Department of Electrical Engineering, State UniÕersity of New York at Buffalo, Amherst, NY 14260-1900, USA Abstract Ž . Investigations into flux-pinning of Bi Sr CaCu O rAg Bi-2212rAg thick film conductors utilizing micron-sized 2 2 2 8qd Ž . Sr,Ca Cu O and nanophase Al O and Au particles are described. Addition of defect particles delayed and reduced 14 24 41 2 3 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 Al O 2 3 Ž . Ž . Ž . reacted rapidly -4 min with 2212-type melts Sr:Ca s1.33–2.07 to form solid–solution Sr,Ca Al O with Sr:Ca ratio 3 2 6 Ž . close to the Sr:Ca composition of the precursor matrix. Addition of nanophase Al O improved the J 1 T over the range 2 3 c Ž . Ž . Ž . 20–30 K, e.g. J 30 K, 1 T rJ 5K,0T s -0.001 , 0.005, and 0.065 for 0%, 10% and 46% molar addition, c c respectively. The addition of nanophase or micron-sized Au completely suppressed 2212 c-axis orientation for the processing temperatures tested. q 2000 Elsevier Science B.V. All rights reserved. PACS: 74.52.D; 74.62.Dh; 74.72.Hs Ž . Ž . Keywords: Bi Sr CaCu O ; Sr,Ca Al O ; Sr,Ca Cu O ; Nanophase Al O ; Nanophase Au; Critical current density; Flux-pin- 2 2 2 8qd 3 2 6 14 24 41 2 3 ning 1. Introduction The practical conductors of Bi Sr CaCu O r 2 2 2 8qd Ž . Ag Bi-2212rAg are of interest for long-length power applications because they can be fabricated by wx low-cost methods such as thick film deposition 1. In addition, they have achieved high transport J in c wx reasonable magnetic fields 2 . The intrinsic flux-pin- ning of Bi-2212 conductors, however, is among the ) Corresponding author. Tel.:q 1-301-975-4954; fax:q 1-301- 975-5334. Ž . E-mail address: timh@nist.gov T. Haugan . worst of the known high temperature superconduc- tors, and is related to their micaceous microstructure wx 2 . The operation temperature of Bi-2212 conductors is limited to - 30 and - 50 K for perpendicular and w x parallel applied magnetic fields, respectively 2,3 . The introduction of artificial flux-pinning defects in Bi-2212 by irradiation shifted the irreversibility line w x f 20 K higher in tapes or crystals 2,4 , and im- proved the magnetic J at all temperatures and mag- c wx netic fields tested 4 . While irradiation gives im- proved flux-pinning, it is considered more costly than chemical methods for the large-scale production of wire conductors. 0921-4534r00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S0921-4534 00 00157-X