Enhancing critical current density of bulk MgB${}_2$ via nanoscale boron and Dy${}_2$O${}_3$ doping

Moderate critical current density (J${}_c$) has been a long-lasting problem in bulk MgB${}_2$ superconductors. We show a certain increment in J${}_c$ of bulk MgB${}_2$ via the use of amorphous boron precursor together with Dy${}_2$O${}_3$ doping. Dy${}_2$O${}_3$ dopant concentration varies from 0 to 2 wt%. X-Ray diffraction (XRD) shows the formation of DyB${}_4$ particles. The critical temperature (T${}_c$) is not affected by Dy${}_2$O${}_3$ doping and stands close to 38 K, showing that there is no Dy interaction with the MgB${}_2$ lattice. Microstructural studies show nanometer-sized MgB${}_2$ grains. A high self-field J${}_c$ of around 380 kA cm${}^{-2}$ is achieved at 20 K within the Dy${}_2$O${}_3$ doping range of 0.5-1.5 wt%. At around 1 wt% Dy${}_2$O${}_3$ doping an improved high-field performance, 90 kA cm${}^{-2}$ at 2 T, 20 K, is observed. In the flux pinning diagram, 1 wt% Dy${}_2$O${}_3$ doping caused a peak shift from 0.19 (0 wt%) to 0.23. This indicates secondary pinning by DyB${}_4$ and lattice strains. Raman studies show the increase in the phonon density of states (PDOS) with increasing Dy${}_2$O${}_3$ doping. (© 2022 The Authors. Advanced Engineering Materials published by Wiley‐VCH GmbH)