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

Abstract

Moderate critical current density (Jc) has been a long‐lasting problem in bulk MgB2 superconductors. We show a certain increment in Jc 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 (Tc) 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 Jc 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.