Enhancing Critical Current Density of Bulk MgB₂ via Nanoscale Boron and Dy₂O₃ Doping

Moderate critical current density (J_c) has been a long-lasting problem in bulk MgB₂ superconductors. We show a certain increment in J_c of bulk MgB₂ via the use of amorphous boron precursor together with Dy₂O₃ doping. Dy₂O₃ dopant concentration varies from 0 to 2 wt%. X-Ray diffraction (XRD) shows the formation of DyB₄ particles. The critical temperature (T_c) is not affected by Dy₂O₃ doping and stands close to 38 K, showing that there is no Dy interaction with the MgB₂ lattice. Microstructural studies show nanometer-sized MgB₂ grains. A high self-field J_c of around 380 kA cm⁻² is achieved at 20 K within the Dy₂O₃ doping range of 0.5–1.5 wt%. At around 1 wt% Dy₂O₃ doping an improved high-field performance, 90 kA cm⁻² at 2 T, 20 K, is observed. In the flux pinning diagram, 1 wt% Dy₂O₃ doping caused a peak shift from 0.19 (0 wt%) to 0.23. This indicates secondary pinning by DyB₄ and lattice strains. Raman studies show the increase in the phonon density of states (PDOS) with increasing Dy₂O₃ doping.