Title :
Formation and growth mechanisms of Bi-2212/Ag composite tapes
Author :
Matsumoto, A. ; Kitaguchi, H. ; Kumakura, H. ; Togano, K.
Author_Institution :
Nat. Res. Inst. for Metals, Tsukuba, Japan
fDate :
3/1/2001 12:00:00 AM
Abstract :
The microstructure changes during the solidification process of Bi-2212 tapes with several nominal compositions of Sr and Ca were investigated using an oil-quenching technique. The formation mechanism was almost the same in all composition tapes. Non-superconducting phases such as Bi-free and Cu-free solid phases exist in the liquid at Tmax. The quantity of the non-superconducting phases of Sr/Ca=1.8/1.2 and 2.2/0.8 tapes was larger than those of the 2.0/1.0 tape. With the solidification of the Bi-2212 phase near the oxide/silver interface, the non-superconducting phases melted into the liquid phase and shrank. Bi-2212 grains grew along the silver interfaces. The high J c enhancement of the Bi-2212/Ag tape was explained by the excellent grain alignments at the oxide/silver interfaces. Locally, biaxially aligned Bi-2212 was observed at the oxide/silver interface for tapes fabricated using melt-solidification under a temperature gradient
Keywords :
bismuth compounds; calcium compounds; critical current density (superconductivity); crystal microstructure; high-temperature superconductors; phase equilibrium; quenching (thermal); silver; solidification; strontium compounds; superconducting tapes; Bi-2212 grains; Bi-2212 phase; Bi-2212/Ag composite tapes; Bi2Sr2CaCu2O8-Ag; biaxially aligned Bi-2212; formation; grain alignment; growth mechanisms; high Jc enhancement; liquid phase; melt-solidification; microstructure; nonsuperconducting phases; oil-quenching technique; oxide/silver interface; solidification process; temperature gradient; Critical current density; Grain boundaries; Heat treatment; Heating; High temperature superconductors; Microstructure; Petroleum; Silver; Solids; Strontium;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
