Enhancing Critical Current Density of Bulk MgB<sub>2</sub> via Nanoscale Boron and Dy<sub>2</sub>O<sub>3</sub> Doping
M. Muralidhar, Kotaro Kitamoto, Sai Srikanth Arvapalli, Dhruba Das, M. Jirsa, M. Murakami, Sri Ramachandra Rao Mamidanna
Abstract
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.