改进型镁扩散法制备高临界电流密度MgB2超导体性能研究

本文采用一种改进型镁扩散法成功制备出密度达到1.95g/cm₃的MgB₂超导块材。论文研究了不同的热处理条件对MgB₂块材的超导转变温度(T_c)和临界电流密度(J_c)性能的影响。采用最佳热处理条件制备的MgB₂超导体T_c和J_c分别达到了38.1K和0.53MA/cm₂(10K,自场)。为了改进镁扩散法MgB₂超导体中弱的高场磁通钉扎性能,本文还研究了nano-Pr₆O₁₁和C掺杂对MgB₂超导体的临界电流密度和不可逆场(H_irr)的影响。结果表明C掺杂的MgB₂超导体临界电流密度在10K,6T下达到了10₄A/cm₂,该结果比未掺杂MgB₂超导体在同样条件下性能提高了两个量级,甚至比固态反应法制备的nano-C掺杂MgB₂超导体性能更好。利用该方法制备的nano-Pr₆O₁₁掺杂的MgB₂超导体在10K,2T下也比未掺杂样品J_c提高达9.4倍。根据大量的实验结果和理论分析我们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MgB₂超导体非常有效的途径。

High critical current density on MgB2 bulks synthesized by an improved Mg-diffusion method

MgB2 bulks with a density, 1.95g/cm3, have been successfully prepared by an improved Mg-diffusion method. The effects of different heat treatment conditions on superconducting transitions temperature, Tc and critical current density, Jc of MgB2 have been discussed. The MgB2 synthesized by optimal heat treatment conditions has the Tc, 38.1K and Jc at 10K, self-field, 0.53MA/cm2. In order to improve poor high field properties in diffusion method, nano-Pr6O11 and C doping effects on Jc and the irreversible field, Hirr of MgB2 have also been studied. The results show that at 10K and 6T the Jc for 15 at.% C-doped MgB2 reaches 104 A/cm2, which is almost two orders of magnitude higher than the undoped one, and better than the nano-C doped MgB2 prepared by solid-state reaction. For the nano-Pr6O11-doped MgB2, the Jc also increases by a factor of 9.4 than the pure sample at 10K and 2T. According to a great of experimental results and theoretic analyses, we propose that the combination of the improved Mg-diffusion method and chemical doing, nanoparticles or C doping, may be an efficient approach to make the MgB2 have excellent Jc and Hirr capability in whole magnetic field.