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A comparative study of the addition of Pb to polycrystalline Ba0.6K0.4Fe2As2 has revealed that the Pb should be added after the Ba0.6K0.4Fe2As2 phase has formed. The uniformly dispersed Pb can ameliorate the Ba0.6K0.4Fe2As2 grain linkages. In contrast, pre-added Pb in the raw powder congregates to form large particles and has hardly any positive effect on the Jc enhancement. To conglutinate at the grain surface and avoid contamination of the Ba0.6K0.4Fe2As2, the material added should have a low melting point and inertia to the superconducting phase. This model also enables us to predict desirable dopants for enhancing superconducting properties of Ba0.6K0.4Fe2As2. [ABSTRACT FROM AUTHOR]

In this paper we report the superconductivity above 40 K in the electron doping single crystals Ca1-xRxFe2As2 (R D La, Ce, Pr). The x-ray diffraction patterns indicate high crystalline quality and c-axis orientation. The resistivity anomaly in the parent compound CaFe2As2 is completely suppressed by partial replacement of Ca with rare-earth elements and the superconducting transition reaches as high as 46 K, which is higher than the value in electron doping FeAs-122 compounds formed by substituting Fe ions with transition metal, and even surpasses the highest value observed in hole doping systems with a transition temperature up to 38 K. The upper critical fields have been determined with the magnetic field along the ab-plane and c-axis, yielding an anisotropy of 2-3. Hall effect measurements indicate that the conduction in this material is dominated by electron-like charge carriers. Our results confirm the feasibility of inducing superconductivity in Ca122 compounds via electron doping using aliovalent rare-earth substitution into the alkaline earth site, which should add more ingredients to the underlying physics of the iron-based superconductors. [ABSTRACT FROM AUTHOR]

Fe-clad BaxK1-xFe2As2 superconducting tapes were fabricated by the ex situ powder-in-tube method combined with a short high-temperature annealing technique. The effects of annealing time and different dopants on the transport properties of BaxK1-xFe2As2 tapes were systematically studied. By co-doping with Ag and Pb, the transport critical current densities Jc of BaxK1-xFe2As2 tapes were significantly improved in the whole field region and the highest transport Jc was up to 1.4 × 10x A cm-2 (Ic D 100 A) at 4.2 K in self-field. It is proposed that the superior Jc values in the co-doped samples are due to the combined effects of Pb doping at low fields and Ag doping at high fields. [ABSTRACT FROM AUTHOR]

Polycrystalline Ba0.6K0.44Fe2As2.2 was fabricated using a two-step solid reaction method by two different sintering processes. Although different microstructures were observed between these samples, similar superconducting properties were obtained. It seems that the sequence for high temperature with short annealing time and low temperature with long sintering time has little effect on the superconducting properties of the Ba0.6K0.44Fe2As2.2 sample. But, for the Ag-added samples, the Jc value was significantly affected by the sintering process, indicating a different mechanism to pure Ba0.6K0.44Fe2As2.2. [ABSTRACT FROM AUTHOR]

We have successfully reached the world record 32.35 T direct-current magnetic field by using a homemade all-superconducting magnet. The magnet has consisted of a 15 T low temperature superconductor outsert coil and two high temperature superconductor no-insulation (NI) insert coils using a conductor tape coated of REBCO (REBa2Cu3Ox, where RE = Y, Gd). This result proves the feasibility of reaching a strong magnetic field up to 32 T by using the NI process as well as the superconductor magnet with insulation. This magnet is one of the essential parts of the 'Synergetic Extreme Condition User Facility' project, which provides expertize, instrumentation, and infrastructure for investigating matter science under extreme physical conditions. We thought that such a strong superconductor magnet would bring the possibility to explore more mystery in physics, medicine, pharmacy, etc. [ABSTRACT FROM AUTHOR]

Second-generation (2G) high-temperature superconducting coated conductors are playing an increasingly important role in power applications due to their large current density under high magnetic fields. In this paper, we conclude and explore the ability and possible potential of J formulation from the mathematical modeling point of view. An equivalent matrix form of J formulation has been presented and a relation between electromagnetic quantities and Karush–Kuhn–Tucker (KKT) conditions in optimization theory has been discovered. The use of the latest formulae to calculate inductance in a coil system and the primal-dual interior-point method algorithm is a trial to make the process of modeling stylized and build a bridge to commercial optimization solvers. Two different dependences of the critical current density on the magnetic field have been used in order to make a comparison with those published papers. [ABSTRACT FROM AUTHOR]

In this paper, the effect of viscous flux flow velocity (u0) on the radial and hoop stresses in a type-II bulk superconductor shaped as a long circular cylinder is discussed for two magnetization processes: the decreasing field after zero-field cooling (ZFC) and field cooling (FC). With increasing u0/R, i.e. u0, as R is the radius of the cylindrical superconductor, the radial and hoop stresses increase and the remagnetization region is reduced. With different values of u0/R, the maximum radial stress is equal to or greater than the maximum hoop stress for the ZFC case, and the maximum radial stress is equal to the maximum hoop stress for the FC case. [ABSTRACT FROM AUTHOR]

We report the fabrication of Ta-sheathed superconducting SmFeAsO1[?]xFx wires by the powder-in-tube method for the first time. The transition temperature of the SmFeAsO0.65F0.35 wires was confirmed to be as high as 52 K. High critical fields Hc2(0)[?]120 T as well as current density Jc of 3900 A cm[?]2 at 5 K were also demonstrated. It should be noted that the Jc exhibits a very weak field dependence behavior, indicating a very encouraging prospect for application of the new superconductors. [ABSTRACT FROM AUTHOR]

Polycrystalline Ba0.6K0.44Fe2As2.2 was fabricated using a two-step solid reaction method by two different sintering processes. Although different microstructures were observed between these samples, similar superconducting properties were obtained. It seems that the sequence for high temperature with short annealing time and low temperature with long sintering time has little effect on the superconducting properties of the Ba0.6K0.44Fe2As2.2 sample. But, for the Ag-added samples, the Jc value was significantly affected by the sintering process, indicating a different mechanism to pure Ba0.6K0.44Fe2As2.2. [ABSTRACT FROM AUTHOR]