提高YBCO高温超导带材各向同性磁通钉扎的研究

Tremendous progress has been made in the scale-up of YBa2Cu3O7-x(YBCO) second-generation (2G) high temperature superconductors (HTS) in recent years. More than one kilometers of 2G HTS tape have now been successfully manufactured.And some of 2G HTS electrical power equipments have been designed and investigated.However, on the one hand, the superconducting properties of YBCO tapes in parallel field and vertical field is different. The anisotropy of YBCO coated conductors is very strong. On the other hand,the superconducting properties of YBCO coated conductors reduce drastically with the applied magnetic field increases. This limits the utility of high-temperature superconductors in electric power applications. Therefore, the enhancement of isotropic flux pinning of YBCO coated conductors is very important for commercialization application and comprehending the flux pinning mechanism of YBCO coated conductors.In this project, YBCO coated conductors will be prepared by chemical solution deposition. And the angular of magnetic field, magnetic field and temperature dependence of critical current density of YBCO films with different defects will be investigated. We will understand the flux pinning mechanism of YBCO films with various defects and establish mathematical model. And on this basis,we will combine different defects to enhance the isotropic critical current density of YBCO coated conductors. And the YBCO conducted conductors exceeding 1000 A cm−1 width at 77 K will be prepared.

近年来，以YBCO为代表的第二代高温超导带材的研究取得了突破性进展，千米级带材已经研制成功，基于YBCO涂层导体的超导电力装置也已经展开设计和实验研究。然而，YBCO超导带材在平行场和垂直场下的超导性能差别很大，存在强烈的各向异性。并且YBCO涂层导体随外加磁场强度增大超导性能急剧下降，大大阻碍了其规模化应用。因此，提高YBCO涂层导体各向同性超导性能的研究不仅具有重大应用需求，同时对理解其磁通钉扎机理也具有重要理论意义。为此，本课题拟在前期工作的基础上，采用化学溶液法制备YBCO涂层导体,研究引入不同类型纳米缺陷对YBCO涂层导体超导性能的影响。通过系统分析临界电流密度（JC）与外加磁场角度、临界磁场强度和温度的依赖关系，理解各种缺陷在YBCO薄膜内部的磁通钉扎机制，建立数学模型。并在此基础上，优化工艺参数制备出临界电流高于1000A/cm、JC在垂直场和平行场相近的YBCO涂层导体。

本项目按照计划首先系统研究了掺杂不同的纳米颗粒（钛酸钡、锆酸钡、锰酸钡以及Gd元素替代）来提高YBCO薄膜的超导性能，优选出能够在YBCO薄膜内作为有效磁通钉扎中心的物质。在此基础上， 根据不同掺杂相在YBCO基体中的微观结构以及提高其超导性能的机制，协同不同形状的纳米柱钛酸钡和纳米点锆酸钡来提高YBCO超导带材的临界电流密度，并系统研究了不同角度下YBCO超导带材的磁通钉扎作用。.通过研究制备掺杂钛酸钡、锆酸钡、锰酸钡以及Gd元素替代的YBCO带材的工艺参数--微观结构—超导性能的依赖关系，明确了确定掺杂纳米异质相的YBCO复合薄膜的主要缺陷类型、尺寸、晶体学特征，理解了掺杂纳米异质相的YBCO复合薄膜的磁通钉扎机理，探索出可以有效改善YBCO超导带材各向异性的途径，掌握了YBCO涂层导体微结构和生长模式的人工调制技术；所制备的协同掺杂纳米BaTiO3和BaZrO3的YBCO带材的临界电流密度在垂直场和平行场下基本一致，均为5.9 MA/cm2，超导层的厚度为2μm，临界电流达到1180A/cm。我们按计划完成了任务，并实现了预期目标。

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