Publication Date:
2015-12-01
Description:
Iron-based superconductors have been considered to be very promising in high-field applications for which multifilamentary wire and tape conductors with high mechanical strength are essential. In this work, 7-,19-, and 114-filament Sr 0.6 K 0.4 Fe 2 As 2 (Sr-122) superconducting wires and tapes with silver as matrix and iron as outer reinforcing sheath were produced by the ex situ powder-in-tube method. The mass densities of Sr-122 phase in 7- and 19-filament conductors were investigated by microhardness characterization, which revealed a positive correlation between hardness and transport critical current density ( J c ) in round wires and flat tapes with various thicknesses. For Sr-122/Ag/Fe 114-filament conductors, in which an average cross-sectional filament size smaller than 50 μ m was achieved by drawing into round wires of 2.0 mm in diameter, the transport J c can be significantly enhanced by flat rolling, as for the 7- and 19-filament conductors. The highest transport J c for Sr-122 filaments in the 7-, 19-, and 114-filament Sr-122/Ag/Fe tapes reached 1.4 × 10 4 , 8.4 × 10 3 , and 6.3 × 10 3 A cm −2 (4.2 K, 10 T), respectively, showing a J c degradation with the increase of filament number. This J c degradation can be ascribed to the sausage effect for SR-122 filaments in longitudinal direction and the grain refinement in these very fine filaments.
Print ISSN:
0021-8979
Electronic ISSN:
1089-7550
Topics:
Physics
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