Critical current density and microstructure of iron sheathed multifilamentary Sr1-xKxFe2As2/Ag composite conductors

Abstract

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 Sr0.6K0.4Fe2As2 (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 (Jc) 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 microns was achieved by drawing into round wires of 2.0 mm in diameter, the transport Jc can be significantly enhanced by flat rolling, as for the 7- and 19-filament conductors. The highest transport Jc of the 7-,19- and 114-filament Sr-122/Ag/Fe tapes reached 1.4x10^4, 8.4x10^3 and 6.3x10^3 A cm-2 (4.2 K, 10 T), respectively, showing a Jc degradation with the increase of filament number. This Jc degradation can be ascribed to the sausage effect for filaments in longitudinal direction and the grain refinement in these very fine filaments.

27 pages, 8 figures

References in corpus (13)

• Superconductivity at 38 K in the iron arsenide (Ba1-xKx)Fe2As2
• Superconductivity up to 37 K in (A1-xSrx)Fe2As2 with A=K and Cs
• Nearly Isotropic superconductivity in (Ba,K)Fe2As2
• Anisotropic thermodynamic and transport properties of single crystalline (Ba${}_{1-x}$K${}_x$)Fe${}_2$As${}_2$ (x = 0 and 0.45)
• Small anisotropy, weak thermal fluctuations, and high field superconductivity in Co-doped iron pnictide Ba(Fe1-xCox)2As2
• Advantageous grain boundaries in iron pnictide superconductors
• High intergrain critical current density in fine-grain (Ba0.6K0.4)Fe2As2 wires and bulks
• Realization of practical level current densities in Sr0.6K0.4Fe2As2 tape conductors for high-field applications
• Biaxially textured cobalt-doped BaFe2As2 films with high critical current density over 1 MA/cm2 on MgO-buffered metal-tape flexible substrates
• High Critical Current Density 4 MA/cm2 in Co-Doped BaFe2As2 Epitaxial Films Grown on (La, Sr)(Al, Ta)O3 Substrates without Buffer Layers
• Hot pressing to enhance the transport Jc of Sr0.6K0.4Fe2As2 superconducting tapes
• Effect of grain refinement on enhancing critical current density and upper critical field in undoped MgB2 ex-situ tapes
• High transport Jc in magnetic fields up to 28 T of stainless steel/Ag double sheathed Ba122 tapes fabricated by scalable rolling process

Cited by in corpus (5)

• Recent advances in iron-based superconductors toward applications
• Superconducting materials: Challenges and opportunities for large-scale applications
• Fabrication and Transport Properties of 100 m Class Sr0.6K0.4Fe2As2 Wires and Pancake Coils
• Fabrication of small superconducting coils using (Ba,A)Fe2As2 (A: Na, K) round wires with large critical current densities
• Enhancement of critical current density in (Ba,Na)Fe2As2 round wires using high-pressure sintering