Wire Development: Oxide Powders
The Oxide-Powder-in-Tube (OPIT) Approach for HTS Conductors
The superconductors in the Bi(Pb)-Sr-Ca-Cu-O (BSCCO) system, namely (Bi,Pb)2Sr2Ca2Cu3Oy (Bi-2223) and Bi2Sr2CaCu2Oy (Bi-2212), are formed into conductors using the OPIT approach. Oxide powders of these superconductors are loaded into silver or sliver alloy tubes, sealed, and then drawn or extruded into round wire. The round wire is then thermally processed to form a superconducting composite, or it is further rolled to produce a flat tape which is then thermally processed to produce a HTS conductor. Most of the conductors produced with the BSCCO materials are made in the tape form. To date, the only practical, long lengths (> 1 km) of HTS conductors have been made with the BSCCO materials. These conductors are closer to commercialization than are the YBa2Cu3Oy (YBCO) coated conductors. Examples of potential commercial products are transmission lines, industrial motors, fault-current limiters, and transformers. American Superconductor is currently building a new production facility with the goal of producing 10,000 kilometers of Bi-2223 tape per year for commercial applications.
(Photo at right: One of the first commercial uses of BSCCO tape will be in transmission lines. Shown at right is a schematic of the type of cable to be used in the Detroit Edison Superconductor Partnership Initiative. Bi-2223 tape is the HTS wire used in the cable.)
(Photo at left: The formation of the Bi-2223 phase takes place in the presence of a lead-rich liquid phase, the Bi-2212 phase, and some alkaline-earth cuprates. Understanding and controlling the fine details of how these phases interact, align, and transform into the Bi-2223 phase would aid in the development of better processing routes which result in higher critical current densities.)
Although the BSCCO HTS conductors are on the verge of commercialization, there is still a need to improve performance and reduce the costs of production in order for the technology to gain a broad acceptance in the commercial marketplace. Recent work at Los Alamos has centered on characterizing the phase development of the superconductor within the composite, developing new processing approaches for increasing the critical current densities ,, and characterizing the microstructure of fully processed BSCCO conductors ,. This work is designed to identify the primary current limiting mechanisms within the conductors, find their origin during the processing of the HTS conductor, and develop new processing technologies that overcome these obstacles and increase the critical current density.
 T. G. Holesinger, A. Ayala, M. B. Ruxandra, and V. A. Maroni, "Investigation of the Initial Stages of Processing Bi-2223 Multifilamentary Tapes by Analytical Electron Microscopy," to be published in IEEE Transactions on Applied Superconductivity, 2001.
 T. G. Holesinger, P. S. Baldonado, N. Van Vo, W. Dai, K. R. Marken, and S. Hong, "Isothermal melt processing of Bi-2212 tapes," IEEE Transactions on Applied Superconductivity, vol. 9, pp. 1800-1803, 1999.
 T. G. Holesinger, J. F. Bingert, J. O. Willis, V. A. Maroni, A. K. Fischer, and K. T. Wu, "The effects of variable oxygen partial pressures during Bi-2223 tape processing," Journal of Materials Research, vol. 12, pp. 3046-3054, 1997.
 T. G. Holesinger, J. F. Bingert, M. Teplitsky, Q. Li, R. D. Parrella, M. P. Rupich, and G. N. Riley Jr., "Spatial variations in composition in high-Jc Bi-2223 tapes," Journal of Materials Research, vol. 15, pp. 285-295, 2000.
 T. G. Holesinger, J. F. Bingert, J. O. Willis, Q. Li, R. D. Parrella, M. D. Teplitsky, M. W. Rupich, and G. N. Riley Jr., "Structural and Compositional Defects in High-Jc Bi-2223 Tapes," IEEE Transactions on Applied Superconductivity, vol. 9, pp. 2440-2446, 1999.