适合于强磁场环境应用的REBCO超导带材研制及磁通钉扎机理研究

The REBa2Cu3O7-δ (REBCO, RE=rare metal elements) second generation high temperature superconducting tape (represented by YBCO), has the characteristics of high Tc, Jc, and Hc2. It has a great market prospect in the field of strong electric power applications, such as electric cables, motors, and high field magnets. REBCO tape has become the first choice of high temperature superconducting applications. At present, great progress has been made in the development of REBCO second generation high temperature superconducting tapes. However, the economic benefit is a bottleneck for the broad application of REBCO high temperature superconducting tape. REBCO superconducting tape has a higher critical magnetic field, and has a high performance price ratio for applications at low temperature and strong magnetic field. It is especially suitable for the applications in the field of superconducting magnets under very strong magnetic fields. Due to the limitation of experimental conditions, the physical properties of REBCO superconducting tapes under strong magnetic field are relatively few. The research of performance under low temperature and high field is a new challenge and hot spot. In the view of the applications of REBCO tape under strong magnetic field, the method of introducing nano-scale artificial flux pinning centers are introduced into REBCO superconducting layer in order to improve the superconducting performance of REBCO superconducting tapes under strong magnetic field. The high field superconducting properties of REBCO tapes and their magnetic flux pinning mechanism will be investigated by using the advanced scientific equipment at High Magnetic Field Laboratory, Chinese Academic of Science (CHMFL). Through the interface microstructure engineering, BaMO3 （BMO,M=Zr，Sn，Hf) and Y2O3 nano-particle doping, as well as combined 1D+2D+3D controllable artificial pinning centers addition, the transport properties of REBCO superconducting thin films under strong magnetic field will be systematically measured and analyzed by using the Steady High Magnetic Field Facilities (SHMFF) at CHMFL. We will clarify the relationship between microstructure and superconducting properties, and the flux pinning mechanism. By improving the performance of doped REBCO film under high magnetic field, its application fields will be expanded. This project not only benefits the better understanding of flux pinning mechanism in REBCO tapes, but also is important for the development of REBCO fabrication process for the applications under strong magnetic fields.

REBCO第二代高温超导带材具有较高的临界转变温度、临界磁场和临界电流密度等特性已成为高温超导应用领域首选材料，其研制已取得很大进展，然而性价比仍是制约其应用的瓶颈。REBCO超导带材在低温强磁场应用领域具有较高的性价比，尤其适合强磁场环境下应用。由于实验条件限制，REBCO超导带材在强磁场下的物性研究还比较少，低温高场下性能研究是一个新的挑战和热点。为此，本项目采用引入人工钉扎中心提高REBCO超导带材在强场下的性能，开展磁通钉扎机理研究。通过BaMO3(BMO,M=Zr，Hf等)掺杂、界面工程和Y2O3掺杂复合1D+2D+3D钉扎中心，人工调制REBCO超导薄膜的微结构，依托合肥稳态强磁场实验装置测试分析REBCO薄膜在强场下的输运性质，研究微结构和输运性质之间的关系，阐明磁通钉扎机制，提高REBCO薄膜在高场下的性能，为大规模制备适合于强磁场环境应用的REBCO超导带材提供依据。

第二代高温超导带材具有较高的临界转变温度、临界磁场和临界电流密度等特性已成为高温超导应用领域首选材料，且其研制已取得很大进展，然而性价比仍是制约其应用的瓶颈。REBCO超导带材在低温强磁场应用领域具有较高的性价比，尤其适合于制作超导磁体等强磁场环境下应用。为此，本项目通过对BHO掺杂YGBCO薄膜、YGBCO/CeO2/YGBCO三层膜和YGBCO/YGBCO+BHO/YGBCO薄膜的结构、形貌和性能的研究，阐明了钉扎机制，探明了提高REBCO超导薄膜在磁场下性能的方法，为大规模制备适合于强磁场环境应用的REBCO超导带材提供依据。本项目确定了BHO掺杂含量为3%-5%，通过优化将200 nm厚度的BHO掺杂YGBCO薄膜临界电流密度从1.25 MA/cm2 提高到4.5 MA/cm2。进一步，通过分步法减弱了厚度效应，制备出微米级厚BHO掺杂YGBCO厚膜，在77 K，自场下临界电流大于150 A。BHO掺杂成功在基质中形成了沿c轴分布的纳米柱缺陷和大量层错，从而能有效提升磁场下性能，在4.2 K和高达30 T的磁场下，临界电流密度超过了1 MA/cm2。其次，通过将稀土元素Gd掺入CeO2薄膜用作中间层，使薄膜内部存在一定量的金属Gd颗粒，促使电流顺利通过该中间层。进一步，通过利用In掺杂CeO2薄膜作中间层，In-CeO2中间层的加入成功抑制YGBCO晶粒的生长，有效抑制厚度效应，进而将样品的Ic提高，样品的临界电流密度最大可以达到7.75 MA/cm2。最后，通过BHO掺杂YGBCO薄膜作为中间层，样品的Tc和77K下的Jc,self相比未掺杂样品的降低程度远小于掺杂样品，这是由于BHO掺杂只存在于薄膜的夹层中，在4.2 K和77 K下都可以提升超导薄膜在磁场下的性能。