磁性纳米粒子掺杂对YBCO超导块材性能的影响及其磁通钉扎机理

Addition of nanoparticles is a practical method to introduce effective flux pinning centers in REBCO high temperature superconductors, while the magnetic nanoparticles, which form much deeper potential wells than the other nanophase inclusions, can exhibit much enhanced flux pinning force in superconductors. In this project, we propose to conduct a study on the addition of magnetic nanoparticles (NiFe2O4 and BiFeO3) in single-domain YBCO bulk superconductors by employing a top-seeded infiltration and growth (TSIG) technique. The interactions of the magnetic dopants with the phases in YBCO and the final distribution of the magnetic particles in Y123 matrix will be identified for elucidating the composite mechanism of the magnetic nanoparticles with the single-domain YBCO bulk. The influence of the magnetic nanoparticle doping on the microstructure, trapped field, levitation force, superconducting transition temperature and critical current density of the YBCO bulk superconductors will be investigated, and the pinning mechanism of the magnetic nanoparticles in YBCO samples will be elucidated for further understanding of the flux pinning mechanism in high temperature superconductors. Moreover, a novel method for introducing multi-source pinning centers of magnetic and YBi2411 nanoparticles will be explored by using the addition of BiFeO3 nanoparticles, which provides a new idea for fabricating high quality bulk superconductors. The study of this project is important for enhancing the flux pinning force of REBCO bulk superconductors and promoting their applications in the fields of superconducting magnet and maglev systems.

纳米粒子掺杂是在REBCO高温超导体内引入有效磁通钉扎中心的实用方法，而磁性纳米粒子可以在超导体内表现出更深的磁通势阱和更强的磁通钉扎能力。本研究拟利用顶部籽晶熔渗生长（TSIG）方法制备NiFe2O4和BiFeO3磁性纳米粒子掺杂的单畴YBCO超导块材。研究磁性掺杂相与YBCO中物相的作用规律、磁性粒子在Y123基体中的分布规律，阐明磁性纳米粒子与YBCO单畴块材的复合机制。研究磁性纳米粒子掺杂对YBCO超导块材的显微结构、捕获磁通、磁悬浮力、超导转变温度及临界电流密度的影响规律，阐明磁性钉扎中心的作用机制，为进一步揭示高温超导体的磁通钉扎机理奠定基础。同时利用BiFeO3掺杂探索一种在YBCO超导体内引入磁性及YBi2411多源纳米钉扎中心的新方法，为发展制备高质量超导块材提供新思路。本研究对提高REBCO超导块材的磁通钉扎能力，推动其在超导磁体、磁悬浮系统等领域中的应用有重要的意义。

单畴YBCO超导块材具有很强的捕获磁通能力和良好的磁悬浮性能，在超导强磁体、磁悬浮轴承和磁悬浮列车等方面具有广阔的应用前景。本项目中，我们一方面进行了对传统制备方法的改进研究，发展出了制备纳米Y-211复合的YBCO超导块材的可靠工艺；另一方面，在纳米复合的超导块材内进行了磁性纳米粒子（NiFe2O4和BiFeO3）掺杂改性的研究工作。使用纳米Y2O3（平均粒径50nm）和BaCuO2的混合物充当固相源，并使用了一种新的液相源成分（Y2O3＋10BaO＋16CuO）成功制备单畴YBCO超导块材，结果表明，Y-123基体中捕获了大量的纳米级Y-211粒子，平均尺寸约为100nm。在此方法中我们进行了纳米NiFe2O4粒子的掺杂研究，发现在最佳掺杂量下，样品（Φ16mm）的磁悬浮力达33.93N，对应力密度约为16.88N/cm2，永磁体充磁下捕获磁通达0.36T。后续工作中，我们又发明了一种新型固相源成分：纳米Y2O3＋BaO＋CuO，同时以纳米Y2O3＋10BaO＋16CuO为液相源，成功制备出纳米复合YBCO单畴块材。由于前驱块都是由初始粉末按比例混合后直接压制，该工艺无需再预制任何前驱粉，这使得整个工艺流程大大简化，制备效率得到极大提高。将纳米BiFeO3粒子掺杂到该方法制备的YBCO超导块材中，发现在最佳掺杂量下，样品（Φ16mm）的磁悬浮力达31.33N，对应力密度约为15.56N/cm2，永磁体充磁下捕获磁通达0.38T。因此，我们的工作对提高单畴YBCO超导块材的制备效率、推动超导体的批量化生产，以及优化样品的性能、提高其实用价值方面有重要的意义。