Synthesis of High Critical Current Density MgB 2 Bulks by an Improved Mg-diffusion Method

Abstract MgB 2 bulks with a density of 1.95 g/cm 3 , were prepared by an improved Mg-diffusion method. The effects of different heat treatments on superconducting transitions temperature T c and critical current density J c of MgB 2 were investigated. The MgB 2 synthesized by the optimal heat treatment has the T c of 38.1 K and J c of 0.53 MA/cm 2 at 10 K, self-field. In order to improve poor high field properties in a diffusion method, nano-Pr 6 O 11 and C doping effects on J c and the irreversible field, H irr of MgB 2 were also studied. The results show that at 10 K and 6 T the J c for 15 at% C-doped MgB 2 reaches 10 4 A/cm 2 , which is almost two orders of magnitude higher than that of the undoped one, and better than that of the nano-C doped MgB 2 prepared by solid-state reaction. For the nano-Pr 6 O 11 -doped MgB 2 , the J c also increases by a factor of 9.4 than that of the pure sample at 10 K and 2 T. According to a lot of experimental results and theoretic analyses, we propose that the combination of the improved Mg-diffusion method and chemical doping of nanoparticles or C, may be an efficient approach to make the MgB 2 have excellent J c and H irr capability in whole magnetic field.