Enhancing critical current density in ex-situ MgB2 via high-temperature sintering with SiC and MgH2 additives

In this study, ex-situ magnesium diboride (MgB2) powders were co-added with 5 wt% silicon carbide (SiC) and varying amounts of magnesium hydride, MgH2 (x = 0, 3, 6 mol.%). All samples were sintered at 900 °C and 1000 °C. X-ray diffraction analysis revealed that sintering undoped samples at 1000 °C reduced MgB2 phase due to the formation of MgB4 and MgO secondary phases. However, the addition of 6 mol.% MgH2 in samples sintered at 1000 °C increased the MgB2 phase fraction to 43.0 %. Scanning Electron Microscopy showed enhanced grain connectivity and smaller grain size, which greatly improved the critical current density to 22517 A/cm2 at 20 K under self-field. The co-addition of MgH2 also improved the Tc-onset from 35.9 K (pure MgB2) to 38.4 K and narrowed transition width, ΔTc. This study shows that the co-addition of MgH2 and SiC to ex-situ MgB2, especially at high sintering temperatures, improved the superconducting properties of the samples.

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