Iron-clad MgB2 superconducting tapes with a MgB2 core cross-section area of 1.07×10−3 cm2 were fabricated using the standard powder-in-tube method. The starting precursor was ultrafine Mg and B mixture powder prepared by high-energy ball milling. Very good grain connections as well as grain refinement were obtained in tapes annealed at 850 °C. Under a 1.5-T external magnetic field, Jc is 1.07×105 and 6.54×103 A/cm2 at 20 and 30 K, respectively. An extrapolation to zero field at 20 K gives a Jc of 3.0×105 A/cm2.

A fabrication process of iron-clad MgB2 superconducting tapes was developed by using a nano-sized precursor and highly deformed iron sheath. Quenching experiments demonstrate that the precursor fully reacts and forms MgB2 under a high pressure of 600 MPa provided by the deformed iron sheath. Very good grain connections as well as a high core density of 2.55 g cm−3 were therefore obtained. High 20 K Jc of 3.1 × 105, 1.6 × 105 and 4.9 × 104 A cm−2 at self-field, 1 and 2 T, respectively, were acquired. The results suggest that using a nano-sized precursor approach to fabricate MgB2 superconducting tape is a very promising process.

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A significant research effort has been made worldwide to introduce nanometre-scale weak superconducting regions into seeded melt-textured superconductors to enhance their critical current density, trapped magnetic field and levitation force. The enhancement in these properties is dependent on the pinning forces exerted on the magnetic flux lines. In this paper we present a substantial improvement in the transport properties of these materials by optimizing the fabrication conditions, controlling the oxygen deficiency, as well as adjusting the doping level of Zn in YBa2(Cu1−xZnx)3O7−δ large grains. The enhancement is found to be as much as 30% by doping between about x = 0.001 25 and 0.002 53. The results strongly indicate that the introduction of local nanometre-scale weak superconducting regions by Zn substitution for Cu in the CuO2 plane enhances the transport properties. Due to the simplicity of the processing conditions, these doping techniques can have a significant potential for a variety of engineering applications.