Materials Research Express, cilt.6, sa.10, 2019 (SCI-Expanded)
In the present study, undoped and coumarin doped bulk MgB2 superconductors were successfully fabricated by using the wet-mixing method and conventional solid-state reaction method. It was found that grain size of the MgB2 samples decreases from 24.3 to 20.5 nm with increasing coumarin content. Actual carbon substitution level in the MgB2 lattice is calculated to be from 0.70% to 1.75% for different coumarin contents. The critical current density and flux pinning force of MgB2 were enhanced by coumarin doping. Among the all MgB2 samples, the highest critical current density value was achieved to be 1 105 A cm-2 in the self field at 5 K. It was obtained that coumarin additive did not reduce superconducting transition temperatures of the MgB2 samples. The results show that coumarin assisted production of MgB2 is a promising way to improve its superconducting properties.