Transport current density at temperatures up to 25 K of Cu/Ag composite sheathed 122-type tapes and wires

Abstract

The fabrication of iron-based superconductors with high transport critical current density (J c ) and low cost is a crucial determinant of whether they can be used for practical applications. In this paper, Cu/Ag composite sheathed Sr 0.6 K 0.4 Fe 2 As 2 (Sr122) tapes and Ba 0.6 K 0.4 Fe 2 As 2 (Ba122) round wires were fabricated via an ex situ powder-in-tube method and heat-treated by the hot pressing and hot isostatic pressing process respectively. In order to thoroughly reveal the application potential of Cu/Ag composite sheathed '122' iron pnictide superconductors, transport J c of tapes and wires in high fields at temperatures up to 25 K was measured. High transport J c of 4.4×10 4 A cm −2 at 4.2 K and 3.6×10 3 A cm −2 at 20 K in 10 T was achieved in Cu/Ag composite sheathed Sr122 tapes. Transport J c of Ba122 wires is 9.4×10 3 A cm −2 at 4.2 K and 1.9×10 3 A cm −2 at 20 K in 10 T. These results demonstrate the great potential of Cu/Ag composite sheathed '122' iron pnictide superconducting tapes and wires for high-field applications at intermediate temperatures around 20 K, which can be easily obtained by using cryocoolers.

High-performance Ba1−xKxFe2As2 superconducting tapes with grain texture engineered via a scalable fabrication

“…Vickers hardness of the Ba122 cores was measured on the cross sections of the tapes. The average values for these tapes are 202, 197, 203 and 212 respectively, which are comparable to that of the previously reported HIP samples [27,30]. The high Vickers hardness usually indicates a high mass density of the superconducting cores.…”

“…The data points can be fitted by the equation f=Ah p (1-h) q with p=0.47, q=1.87. The fitting curve peaks at h0=0.20, indicating that the pinning mechanism is more close to the grain boundary pinning when compared with our previous hot pressed tape whose h0 locates at 0.22 [25,27,41]. This is in accordance with the fact that large amount of small grains caused by low temperature sintering exist in the high-performance tape.…”

“…As an alternative to uniaxial pressing for densification, the hot isostatic pressing (HIP) process utilizing highpressure argon gas as media can effectively reduce the pores and cracks in superconducting cores. The J c values of~10 4 A cm −2 at 4.2 K and 10 T were measured in HIP round wires with randomly oriented grains [26,27]. The mass density of iron-pnictide cores of wires and tapes can be indicated with Vickers hardness.…”

“…The mass density of iron-pnictide cores of wires and tapes can be indicated with Vickers hardness. It is reported that the mass density of Ba122 cores in HIP processed wires can be significantly enhanced to nearly 100%, showing Vickers hardness even higher than that in uniaxially pressed tapes [24,[26][27][28][29]. Compared with uniaxial pressing, HIP technique is much more flexible and economic for large-scale producing, since long length wires and tapes can be processed in winding state in space-limited furnaces.…”

Significant enhancement of transport Jc in Cu/Ag-sheathed (Ba,K)Fe2As2 superconducting tapes by pre-composite technique

“…Since the Cu/Ag composite tapes will melt in a wide range at 770°C and above, the sintering temperature should be selected below 770°C. The previous studies show that the optimal sintering temperature for Cu/Ag tapes is above 740°C [39]. Therefore, the sintering temperature is optimized between 740 and 770°C.…”