YBCO超导涂层厚度与其临界电流密度的关系研究

Second generation high temperature superconducting (2G HTS) wire, YBa2Cu3O7-δ (YBCO) coated conductor namely, is a potential material for the superconducting power devices at the liquid nitrogen temperature of 77K and has been rapidly scaled up to routine pilot-scale manufacturing. However, the high price of 2G HTS wire in the range of $300 and $500 for every kA-m (Ic×length value) is a severe challenge for its large-scale practical applications at present. In order to enhance carrying capacity and achieve further market penetration, besides improving critical current performance in magnetic fields and the production throughput to reduce the cost/performance ratio, increasing thickness of YBCO film is also another important route. However, the plenty of experiments show that the critical current density (Jc) will usually decrease with the film thickness exceeding 0.6 micrometer. To our knowledge, there are less systematic studies on the relationship between Jc and thickness of film up to date. .Based on our previous works on the YBCO coating conductors, the YBCO film with thickness ranging from 0.5 to 10 micrometer will be prepared by the solution-based metal organic deposition (MOD) and magnetron sputtering methods respectively in this proposal. By comparing the microstructure and superconducting performance of YBCO film with various thickness and prepared by different methods, the variation principle of Jc depending on different microstructures in film will be investigated to achieve the optimal parameters for preparing the thick film with outstanding superconducting performance. Subsequently the possible route for improving the film quality and increasing the Jc of thick film will also explored by introducing the 10 nm interlayers to relieve the stress in film and pinning centers simultaneously. All above research can offer theoretical and technical support for 2G HTS wire manufacturing and application.

第二代高温超导带材（也被称为YBCO涂层超导体）是液氮温区下超导强电应用的首选材料，已实现小批量生产，但每千安米带材的价格在300-500美元之间，极其昂贵，严重制约其大规模应用。提高其性价比的途径之一就是增加其中的YBCO超导涂层厚度，从而提高其载流能力。但大量的实验表明：当超导涂层厚度大于0.6μm后，随厚度的增加，临界电流密度Jc剧烈下降。目前，对Jc和超导涂层厚度的关系尚无系统性研究。本课题将在前期大量的超导涂层制备的基础上，采用化学溶液法和物理气相沉积法分别制备厚度在0.5-10μm厚的超导涂层，通过对比不同方法制备的、不同厚度涂层的微观结构和超导性能等，研究超导涂层Jc随微观结构的变化规律，及其与制备工艺的对应关系；通过在超导涂层中间引入10 nm厚的插入层松弛薄膜应力、改善薄膜质量，同时引入钉扎中心来探索提高厚膜Jc的可能途径，为二代带材的大规模工业应用奠定理论和技术基础。

本课题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、铈酸钡以及氧化铁等）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，并制备出具有高临界电流密度的YBCO复合薄膜。在此基础上，制备了一系列不同厚度的含有纳米颗粒的YBCO复合膜，研究了YBCO膜超导临界电流对薄膜厚度的依赖关系，明确了YBCO膜随厚度增加超导性能下降的部分原因。然后，在YBCO厚膜之间引入极薄的BaTiO3、CeO2和CaTiO3薄膜，探索出一条抑制超导厚度效应的有效途径，初步掌握了YBCO涂层导体微结构和生长模式的人工调制技术；所制备的YBCO/YBCO/BaTiO3/YBCO/YBCO的多层复合厚膜的最大厚度达到2.7 μm，其中厚度为2.0 μm的YBCO复合厚膜在77 K, 5 T 下的临界电流密度达到0.5 MA/cm2，在77K自场下的的临界电流密度达到2.7 MA/cm2，临界电流达到540 A/cm。此外，采用低氟法制备出了厚度为5 μm ~10μm的YBCO厚膜，其中，5 μm厚的YBCO膜的临界电流密度超过1.2 MA/cm2。项目执行期间，发表SCI论文10篇，申请和授权专利11项，圆满完成任务，并实现了预期目标。