Origin of J(c) lateral spatial distribution in Ag-sheathed Bi-2212 HTSC tapes

• Published in: IEEE transactions on applied superconductivity Vol. 7; no. 2; pp. 1331 - 1334
• Main Authors: Pan, A V, Ionescu, M H, Dou, S X
• Format: Journal Article
• Language: English
• Published: 01.06.1997
• ISSN: 1051-8223
• DOI: 10.1109/77.620773

Critical current density (J(c)) spatial distribution in the superconducting core of the Ag-sheathed Bi-2212 tapes prepared by "powder in tube" technique has been measured by means of tape cutting along the rolling direction to a few narrow strips and separate J(c) measurements each of them. The J(c) value on the edges of tapes has been found to be higher by a factor of about 3 in comparison with the central area. Unexpectedly, the measured oxide core density is shown to be in contrary the lowest in the edge regions. The thin interface layer (about 10 mum thick) with no secondary phase has been observed by SEM on the whole circumference of Ag-sheath/core boundary. This interface layer is assumed to be responsible for the dominant contribution to the supercurrent-carrying ability of a tape. However, in fact the J(c)-values on the very edge of the core still are twice as high as J(c) in the central region (3.6x10(4) against 1.8x10(4) A/cm (2)). Thus, an optimal structure formation can be promoted by the core edge geometry