改进型镁扩散法制备高临界电流密度MgB_2超导体性能研究（英文）

Synthesis of High Critical Current Density MgB_2 Bulks by an Improved Mg-diffusion Method

采用一种改进型镁扩散法成功制备出密度达到1.95g/cm^3的MgB_2超导块材。研究了不同的热处理条件对MgB_2块材的超导转变温度和临界电流密度性能的影响。采用最佳热处理条件制备的MgB_2超导体T_c和J_c分别达到了38.1K和0.53MA/cm^2(10K,自场)。为了改进镁扩散法MgB_2超导体中弱的高场磁通钉扎性能,还研究了nanao-Pr_6O_(11)和C掺杂对MgB_2超导体的临界电流密度和不可逆场的影响。结果表明C掺杂的MgB_2超导体临界电流密度在10K,6T下达到了104A/cm^2,该结果比未掺杂MgB_2超导体在同样条件下性能提高了2个量级,甚至比固态反应法制备的nano-C掺杂MgB_2超导体性能更好。利用该方法制备的nanao-Pr_6O_(11)掺杂的MgB_2超导体在10K,2T下也比未掺杂样品Jc提高达9.4倍。根据大量的实验结果和理论分析作者提出基于改进型镁扩散法和化学掺杂,包括纳米粒子和C掺杂,很有可能是一种制备高性能MgB_2超导体非常有效的途径。

MgB2 bulks with a density of 1.95 g/cm3, were prepared by an improved Mg-diffusion method. The effects of different heat treatments on superconducting transitions temperature Tc and critical current density Jc of MgB2 were investigated. The MgB2 synthesized by the optimal heat treatment has the Tc of 38.1 K and Jc of 0.53 MA/cm2 at 10 K, self-field. In order to improve poor high field properties in a diffusion method, nano-Pr6O11 and C doping effects on Jc and the irreversible field, Hirr of MgB2 were also studied. The results show that at l0 K and 6 T the Jc for 15 at% C-doped MgB2 reaches 10^4A/cm2, which is almost two orders of magnitude higher than that of the undoped one, and better than that of the nano-C doped MgB2 prepared by solid-state reaction. For the nano-Pr6OH-doped MgB2, the Jc also increases by a factor of 9.4 than that of the pure sample at l0 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 MgB2 have excellent Jc and Hirr capability in whole magnetic field.