Enhanced magnetic field dependent critical current density of MWCNT doped magnesium diboride superconductor

MgB2 bulk samples added with multiwall carbon nanotube (MWCNT) were synthesized by powder–in–sealed tube (PIST) method. The effect of MWCNT doping on the structural and superconducting properties of MgB2 superconductor were investigated. The XRD analysis reveals the hexagonal structure of MgB2 in all the samples. FESEM, TEM and Raman analysis indicate the microstructural changes due to MWCNT doping. Raman spectra show the shifting of the E2g peak is more for lightly doped samples. DC magnetization measurement shows a sharp superconducting transition in all the samples and a slight reduction in critical temperature (Tc) for the doped samples. The Jc(B) characteristics of doped samples show a significant enhancement of Jc compared with pristine MgB2 at 10 and 20 K. MgB2 doped with 1 and 2 wt% MWCNT show maximum enhancement in Jc i.e., 1.3 ×105 and 1.1 ×105 A/cm2 at 5 T and 10 K, respectively, while heavily doped (5 wt%) sample shows lower Jc(B) characteristics. The flux–pinning properties of MWCNT doped MgB2 have been enhanced due to the formation of point pinning centers.