Superior critical current density obtained in MgB2 bulks via employing carbon-coated boron and minor Cu addition.

High performance Cu doped MgB 2 bulks were prepared by an in-situ method with carbon-coated amorphous boron as precursor. It was found that the usage of carbon-coated boron in present work leads to the formation of uniformly refined MgB 2 grains, as well as a high level of homogeneous carbon doping in the MgB 2 samples, which significantly enhance the J c in both Cu doped and undoped bulks compared to MgB 2 bulks with normal amorphous boron precursor. Moreover, minor Cu can service as activator, and thus facilitates the growth of MgB 2 grains and improves crystallinity and grain connectivity, which can bring about the excellent critical current density ( J c ) at self fields and low fields (the best values are 7 × 10 5 A/cm 2 at self fields, and 1 × 10 5 A/cm 2 at 2 T, 20 K, respectively). Simultaneously, minor Cu addition can reduce the amount of MgO impurity significantly, also contributing to the improvement of J c at low fields. Our work suggests that Cu-activated sintering combined with employment of carbon-coated amorphous boron as precursor could be a promising technique to produce practical MgB 2 bulks or wires with excellent J c on an industrial scale. [ABSTRACT FROM AUTHOR]