Microstructure and superconducting properties of MgB2 bulks prepared from Mg + B + Mg(BH4)2 composites.

Practical applications of the MgB2 prepared by the in situ method are usually limited because of the pores formed by the volatility of Mg. In order to improve the performance of MgB2 bulks, MgB2 bulks were fabricated through an in situ synthesis method with composites of B powder, Mg powder, and 10–100 wt% Mg(BH4)2 powder. The superconducting properties and grains structure of these MgB2 bulks were investigated, such as onset superconducting transition temperature (Tc), critical current density (Jc), porosity, resistivity (ρ), and grain connectivity. For the MgB2 bulk prepared from 80 wt% Mg(BH4)2 powder added composites, the Jc (1 T) value at 5 K was 4.1 × 105 A cm−2 and the onset Tc value was 37.5 K. Moreover, the microstructure of these MgB2 bulks was also analyzed using scanning electron microscope (SEM). The MgB2 bulk with less pores can be prepared with moderate Mg(BH4)2 powder added composite as precursor. The composites also provide raw materials for preparing high-quality in situ MgB2 superconducting wires. [ABSTRACT FROM AUTHOR]