Large transport J(c) in Cu-sheathed Sr(0.6)K(0.4)Fe2As2 superconducting tape conductors.

He Lin,Qianjun Zhang,Chao Yao,Chiheng Dong,Yanwei Ma,Xianping Zhang,Dongliang Wang,Haitao Zhang

doi:10.1038/srep11506

He Lin, Qianjun Zhang + Show 6 more

Open Access

https://doi.org/10.1038/srep11506

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Abstract

Copper sheath is the first choice for manufacturing high-Tc superconducting wires and tapes because of its high electrical and thermal conductivities, low-cost and good mechanical properties. However, Cu can easily react with superconducting cores, such as BSCCO, MgB2 and pnictides, and therefore drastically decrease the transport Jc. Here, we report the fabrication of Cu-sheathed Sr1−xKxFe2As2 tapes with superior Jc performance using a simple hot pressing method that is capable of eliminating the lengthy high-temperature sintering. We obtained high-quality Sr1−xKxFe2As2 tapes with processing at 800 oC for 30 minutes and measured high Tc and sharp transition. By this rapid fabrication, Cu sheath does not give rise to apparent reaction layer, and only slightly diffuses into Sr-122 core. As a consequence, we achieved high transport Jc of 3.1 × 104 A/cm2 in 10 T and 2.7 × 104 A/cm2 in 14 T at 4.2 K. The in-field Jc performance is by far the highest reported for Cu-sheathed high-Tc conductors. More importantly, Cu-sheathed Sr-122 tapes also showed a high Je value of 1.0 × 104 A/cm2 in 10 T at 4.2 K, which has reached the widely accepted practical level for applications. These results demonstrate that Cu is a very promising sheath for the practical application of pnictide conductors.

Highlights

Cu can react with superconducting cores, such as BSCCO, MgB2 and pnictides, and drastically decrease the transport Jc
Zhang et al systematically studied the effect of various sheath materials (Nb, Ta and Fe/Ti) on the microstructure and superconducting properties of SmFeAsO1−xFx wires and reported consistent formation of a thick reaction layer between the core and metal sheath, which hinders the performance of transport Jc9
Ag-sheathed Ba-122 and Sr-122 conductors have been investigated intensively, and high Jc exceeding A/cm[2] (Maximum Jc = 1.2 × A/cm2) at 4.2 K and 10 T has been reported by applying uniaxial pressing, such as hot pressing (HP) and cold pressing (CP)[15,16,17,18,19]

Summary

Introduction

Cu can react with superconducting cores, such as BSCCO, MgB2 and pnictides, and drastically decrease the transport Jc. Here, we report the fabrication of Cu-sheathed Sr1−xKxFe2As2 tapes with superior Jc performance using a simple hot pressing method that is capable of eliminating the lengthy high-temperature sintering. During the final heat treatment, we introduce a hot pressing process with combination of short-time sintering (800 °C/30 min or 700 °C/60 min) and low external pressure (~20 MPa) This rapid fabrication can effectively avert the formation of reaction layer, and result in a high transport Jc of 3.1 × 104 A/cm[2] at 4.2 K and 10 T

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