Effect of Ti_3SiC_2 doping on critical current density and flux pinning in MgB_2

摘要

Ti_3SiC_2 is used as the dopant, which not only provides C source for C substitution for B in the MgB_2 lattice, but also produces more non-superconducting precipitates locating in MgB_2 grain boundaries acting as the pinning centers. Carbon substitution of boron can be confirmed by the (100) peak of MgB_2 shift behavior with increasing Ti_3SiC_2 doping level. The critical current density (Jc) values are determined by M-H hysteresis loops. In low magnetic fields, the J_c values for the undoped sample are higher than that for the doped samples. However, with increasing magnetic fields, the J_c values for the doped samples are found to be enhanced for MgB_(1.9)(Ti_3SiC_2)_(0.05) and MgB_(1.85)(Ti_3SiC_2)_(0.075). The flux pinning behavior has been investigated and it reveals that the flux pinning force can be improved by Ti_3SiC_2 doping, when the non-superconducting phases uniformly distribute in MgB_2 matrix and they do not depress the intergrain connectivity.