Fabrication of Bi-2223 Ag–Au–Mg alloy sheathed tapes with a controlled melting process

Bi-2223 Ag-Au-Mg alloy sheathed tapes with J, (77 K, 0 T) up to 28.5 kA/cm(2) were fabricated by a controlled melting (CM) process. It was found that the CM process is effective for eliminating weak links and improving the transport properties of Bi-2223 Ag-Au-Mg alloy sheathed tapes. The compressive stress in the Ag alloy/oxide interface induced by the fast cooling is decreased due to the low thermal conductivity of the Ag-Au-Mg alloy sheath. There is no microcracking observed at the interface of the fast-cooled sample. The microstructure analysis demonstrates that the Bi-2223 phase decomposition is accelerated with the increase of the melting temperature. Too high melting temperature may cause severe phase segregation, which is unrecoverable in the subsequent heat treatments. (C) 1999 Elsevier Science B.V. All rights reserved.