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

Abstract

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 T_c-onset from 35.9 K (pure MgB₂) to 38.4 K and narrowed transition width, ΔT_c. 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.