铁基超导材料原位烧结织构形成机制及其载流能力研究

The Fe-based superconducting materials have a wide application prospect due to their higher transition temperature and excellent upper critical field. However, the development of Fe-based superconducting materials application is limited by their poor current carrying capability. How to improve current carrying capability of Fe-based superconducting materials has become the hot topic of research in the superconducting field. Recently, it is found that the critical current density in the Fe-based superconducting materials is remarkably deteriorated due to the presence of weak link grain boundary. Formation of texture in the Fe-based superconducting materials can decrease the weak link grain boundary and thus significantly improve current carrying capability through reducing the misorientation between grains. In present project, it is proposed that the formation of texture in the Fe-based superconducting materials can be realized effectively and conveniently during their in-situ sintering process with addition of proper sintering aid. Based on the formation kenitics of superconducting phase in the Fe-based superconducting materials prepared by sintering, proper sintering aid will be determined to add into the in-situ sintering process of Fe-based superconducting materials and form low-temperature sintering liquid in which the superconducting phase can be acceleratedly formed and dissolved. Then the regulatable texture of superconducting phase that possesses excellent grain connectivity will be formed from this sintering liquid through controlling process parameters (concentration,temperature, etc). The sucessful implementation of this project can obviously improve current carrying capability of Fe-based superconducting materials and promote their practical application. Moreover, the formation kenitics of superconducting phase during sintering process and the relationship between the microstructure morphology and current carrying capability in the Fe-based superconducting materials will be clarified, which can provide theoretical guidance for the fabrication of Fe-based superconducting materials with higher superconducting properties in future.

铁基超导材料因其较高的超导转变温度和优异的上临界场，在高磁场领域有很广阔的应用前景。但目前制备的铁基超导材料的载流能力都比较低，远远达不到实用要求。如何提高铁基超导材料的载流能力成为超导领域的研究热点。由于铁基超导体中存在晶界弱连接现象，在铁基超导材料中形成一定的织构可以降低晶粒间取向差，从而达到显著提高其载流能力的目的。据此，本项目提出在铁基超导材料原位烧结过程中添加合适烧结助剂，简便、有效地形成超导织构的设想。拟在澄清铁基超导材料烧结成相动力学机制的基础上，选取合适的烧结助剂，在烧结过程中引入低温活性液相，促进超导相形成与溶解，然后通过温度和浓度等工艺参数的控制，重新析出形成晶间连接良好的超导相织构。本项目的成功实施有望大幅提高铁基超导材料的载流能力，同时也可以获得铁基超导材料中烧结成相机理以及微观组织结构与超导性能之间的一般规律，为进一步合成具有更佳超导性能的铁基超导材料提供参考。

铁基超导材料因其较高的超导转变温度和优异的上临界场，在高磁场领域有很广阔的应用前景。但目前制备的铁基超导材料的载流能力都比较低，远远达不到实用要求。如何提高铁基超导材料的载流能力成为超导领域的研究热点。由于铁基超导体中存在晶界弱连接现象，在铁基超导材料中形成一定的织构可以降低晶粒间取向差，从而达到显著提高其载流能力的目的。据此，本项目阐明了铁基超导材料、尤其是“11”型铁基超导材料烧结过程中成相动力学机制以及晶体生长机理，并通过烧结工艺参数优化大大改善了其超导性能；确定了多种金属添加剂（如Sn和Mg），能够显著影响铁基超导材料烧结成相过程和微观组织，促进超导相层状晶体织构的形成，明显改善了铁基超导材料的晶间连接性和载流能力，尤其是其高磁场下的临界电流密度与未添加金属的样品相比提高了一个数量级以上，并且随磁场增加没有明显的衰减，在60000 Oe下仍能达到3×102 A cm−2；初步总结了铁基超导材料不同微观组织结构与超导性能之间的一般规律。除此之外，结合当前研究热点，还进一步开展了11型铁基超导薄膜的成相机制和组织控制的研究。通过厚度调整和金属层覆盖在FeSe膜中引入了电子掺杂，从而改变了超导薄膜的载流子浓度，有效优化了超导电性，其中最高超导转变温度达到了16.2K。在以上研究的基础上，制备出了两种高载流的FeSe0.5Te0.5超导块材样品和一种高质量的FeSe超导薄膜，培养研究生4名，发表SCI检索高水平论文13篇，获得国家授权专利3项。本项目相关研究结果为制备高载流的铁基超导线材和带材奠定了较好的基础，尤其是金属掺杂和金属覆层处理开辟了一条新的提高铁基超导性能的途径，并为探明铁基超导机制提供了有价值的线索。