The object of this investigation is to improve the flux pinning and critical current density (Jc) of bulk MgB2 materials for daily applications including superconducting permanent magnets. We prepared two sets of bulk MgB2 materials employing commercial high-purity powders of Mg metal and carbon-coated amorphous B using a single-step solid-state reaction process. The first set of samples was produced by a single-step solid-state reaction at various temperatures between 794 °C and 806 °C in steps of 3 °C in pure argon atmosphere to optimize the sintering temperature. Further, the second set of samples was produced from Mg-rich MgB2 material adding 1.5 wt% carbon-coated amorphous B powder to it, combined with 4 wt% of silver. X-ray diffraction analysis showed that samples were single-phase MgB2 with minor trace of impurities. In all samples, sharp superconducting transition temperatures were observed around 38 K, which was decreased around 1 K in MgB2 material produced with 1.5 wt% of carbon encapsulated boron. The critical current densities in Mg-rich MgB2 material with 4 wt% of Ag were lower than in silver-free MgB 2 bulks. The sample with 1.5 wt% of carbon-coated B exhibited the highest Jc of 460 kA/cm2 at 20 K and self-field. Our results demonstrate a strong correlation between the microstructure achieved and the resulting pinning performance.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering