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.