Processing and characterization of Ag-clad Bi-2223 superconductors

Practical applications of high-temperature superconductors will be governed by their current transport and mechanical characteristics. With careful control of the processing parameters high-quality long-length mono- and multifilament Bi-2223 conductors have been fabricated by the powder-in-tube technique. A critical current density (J/sub c/) of up to 1.2/spl times/10/sup 4/ A cm/sup -2/ has been observed at 77 K in a 1260-m-long multifilament conductor containing 37 monocore filaments. A high-temperature superconducting magnet and a prototype transformer were fabricated and characterized from such long-length conductors. Extensive studies on the in-situ strain characteristics of the mono- and multifilament conductors have been conducted. Multilayer silver/superconductor composite tapes, fabricated by a novel chemical etching technique, were also observed to exhibit improved strain tolerance characteristics. To further improve the current characteristics of the Bi-2223 tapes the wire-in-tube technique was adopted. A J/sub c/ value >10/sup 5/ A cm/sup -2/ at 77 K and in self field have been obtained in a Bi-2223 tape fabricated by the wire-in-tube method.