Development of advanced MgB_2 superconducting tapes by controlling microstructure

点击翻译按钮获取中文摘要

We have improved critical current density (Jc) of MgB_2 superconducting tapes by the refinement of MgB_2 powder Ex-situ processed tapes using commercially available MgB_2 powders soaked in organic acid solutions show the improvement in transport Jc. This improvement is attributed to the grain pulverization and carbon substitution. The former is probably associated with the dissolution of MgO layers attaching to the MgB_2 grains. On the other hand, the latter originates from the remnant organic solvent adsorbing to the surface of MgB_2. The grain refinement increases the area of grain boundaries that acts as pinning centers. The carbon substitution increases upper critical field (Bc_2) Therefore, these effects successfully improve the Jc values of the tapes. The Jc values at 4.2 K and 10 T reach 4kA/cm^2 by the chemical treatment. This value corresponds to the tenfold increase, compared with the values of tapes using pristine MgB2 powders without treatment.This process is easy and low-cost which is suitable for the fabrication of long wires and tapes. Furthermore, this is applicable to other processes, such as ball-milled powders, and further improvement in Jc can expected.