arXiv subjects

Zhongtang Xu

Publications and source records attributed to Zhongtang Xu.

4 recordsLinked to original sources

arXiv2018

Superconducting joint between iron-based superconductor tapes

Superconducting joints are essential for iron-based superconductor's applications in future. In this study, a process for fabricating superconducting joints between Sr1-xKxFe2As2 (Sr-122) tapes is developed for the first time. The Ag sheath was peeled off from one side of each sample. The exposed superconducting parts of the two tapes were joined and wrapped again with Ag foil. The diffusion bonding of the iron-based superconducting joint was achieved by hot-pressing process in Argon atmosphere. The superconducting properties, microstructures and the elements distribution of the joint regions had been investigated. The pressure and pressing times were optimized in order to enhance the transport current of the joints. At 4.2 K and 10 T, a transport critical current Ic of 57 A for the joint was obtained, which is approximately 63.3% of the current capacity of the tapes themselves. Furthermore, the joint resistances dV/dI were estimated from the V-I curve of the joints and the calculated joint resistances values are below 10^-9 Ohm. These results demonstrate that the hot pressing was useful for fabricating the superconducting joint samples.

cond-mat.supr-con↗

arXiv2017

Transport properties of ultrathin BaFe1.84Co0.16As2 superconducting nanowires

Superconducting nanowire single-photon detectors (SNSPDs) have an absolute advantage over other types of single photon detectors except the low operating temperature. Therefore, many efforts have been devoted to find high-temperature superconducting materials that are suitable for preparing SNSPDs. Copper-based and MgB2 ultra-thin superconducting nanowires have been already reported. However, the transport properties of iron-based ultra-thin superconducting nanowires have not been studied. In this work, a 10 nm thick 200 nm wide 30 μm long high quality superconducting nanowire was fabricated from ultrathin BaFe1.84Co0.16As2 films by a lift-off process. The precursor BaFe1.84Co0.16As2 film with a thickness of 10 nm and root-mean-square roughness of 1 nm was grown on CaF2 substrates by pulsed laser deposition. The nanowire shows a high superconducting critical temperature Tzero c=20 K with a narrow transition width of Delta T=2.5 K and exhibits a high critical current density Jc of 1.8E7 A/cm2 at 10 K. These results of ultrathin BaFe1.84Co0.16As2 nanowire will attract interest in electronic applications, including SNSPDs

cond-mat.supr-con↗

arXiv2017

Fabrication and Transport Properties of 100 m Class Sr0.6K0.4Fe2As2 Wires and Pancake Coils

Iron-pnictides are hotly studied since 2008 in the superconducting materials research area, due to their special properties and unclear mechanism. Big achievement has been made in the pnictide research during the past years. For practical uses, pnictide superconductor should be fabricated in a long wire form which can be used for different devices. In this work, 100 m class 7-core Sr0.6K0.4Fe2As2 (Sr122) tapes have been made using the powder-in-tube technique, which is reported for the first time. Clearly, an average Jc of 1.3x10^4 A/cm^2 at 10 T was reached over the 115 meter length, showing a high property and good uniformity of 100 meter level Sr122 tapes. Using the 10 m long Sr122 tapes, two double-pancake coils were fabricated by a wind and reaction technique. No transport current could be measured for the coil made from the mono-filamentary tape. However, transport Ic was obtained in the coil made from the 7-filamentary tape. The factors which affect the superconducting property of the coil were discussed in this work.

cond-mat.supr-con↗

arXiv2015

High performance FeSe0.5Te0.5 thin films grown at low temperature by pulsed laser deposition

We report on fully epitaxial FeSe0.5Te0.5 (FST) thin films with high-quality grown on CaF2 (00l) substrate at a low temperature of 300°C by pulsed laser deposition. The transport Jc of thin films is up to 1.36 MA/cm2 in self-field and 0.97 MA/cm2 in 9 T at 4.2 K, indicating very weak field dependence. A nearly isotropy of Jc (γ= Jc(H//ab)/Jc(H//c) as low as 1.09 at 9 T is achieved in the FST thin films. Moreover, no clear amorphous interfacial layer presents between the film and the substrate probably ascribing to low temperature and low laser repetition rate grown, while the thickness of reaction layer is approximate 5 nm in many other works. The evidences of transmission electron microscopy show some lattices with lateral size of < 5 nm x 20 nm seem to be disturbed. Those location defects are thought to be responsible for nearly isotropic behavior of superconductivity.

cond-mat.supr-con↗