层状硫属化合物电热输运协同调控的同步辐射研究

In order to tackle the essential issue of electron-phonon interaction and their transport behaviors in during their thermoelectric conversion process, we must simultaneously achieve precise characterization of the defect structure, local atomic structure, as well as the electronic band structure in these thermoelectric systems. However, due to the limitation of characterization facilities and methods, experimental study on this issue is still quite scarce. Owing to its great sensitivity to the local atomic structure and chemical environment around the target atoms, synchrotron radiation X-ray absorption spectroscopy (srXAS) can be seen as a powerful tool to study the local structure information in solids and acquire their fine atomic structures. Meanwhile, synchrotron radiation angle-resolved photoelectron spectroscopy (srARPES) can provide information of the momentum, energy, and lifetime of photon-generated electrons, which can reveal the potential morphology of the band structure, such as the distribution of the energy band and position of the Fermi surface, and greatly enhance our ability to explore the band structure in solid matter. Benefiting from the above advanced characterization techniques, together with some strategies for modulation of defect structure, such as ions modification, doping, substitution and embedding, this project will present a deep study of the electron-phonon structure and their interaction to obtain the basic laws governing the electro-thermal transport behavior in layered chalcogenides compounds. Through the implementation of the project, newly developed optimization strategy based on the synergistic modulation of the electron-phonon transport behaviors will be established, which could help to obtain a batch of layered chalcogenides-based high-performance thermoelectric materials, and provide strong material support for the industrial application of thermoelectric technology.

为了研究热电转换过程中最本质的问题—热电材料中电声相互作用及输运行为，我们必须同时解决材料的缺陷/局域/能带结构的精确表征问题，但是由于表征手段的限制，实验研究还相当匮乏。同步辐射X射线吸收谱技术由于具有对中心吸收原子的局域结构和化学环境敏感等特征，提供了一种强有力的结构探测手段来探测固体的局域结构信息。同步辐射角分辨光电子能谱技术能够给出样品光生电子的动量、能量、寿命等信息，从而揭示样品的能带分布和费米面等潜在的电子结构，极大的增强了我们探测固体能带结构的能力。本项目拟通过离子修饰、掺杂、取代及嵌入等策略，结合同步辐射X射线吸收谱以及角分辨光电子能谱等先进实验表征技术，深入研究层状硫属化合物热电转化过程中其电声结构、电声相互作用以及电热输运行为的基本规律，获得电声输运协同调控提高热电转化效率的新途径，开发一批基于层状硫属化合物的高效热电转换新材料，为高效热电转化利用提供关键材料。

本项目围绕热电转换过程中最本质的问题—热电材料中电声相互作用及输运行为，利用同步辐射角分辨光电子能谱等先进表征技术，针对热电转换材料的缺陷/局域/能带结构，进行了了深入研究。提出了一种“高效层间电荷释放”的实验策略，通过在BiCuSeO中引入高浓度非本征电荷和构筑层间电荷传输通道促进受限电荷的充分释放，获得了823K时达到1.4的优异热电性能；发现了具有本征不饱和负磁阻的范德华结构材料FeNbTe2，从而揭示了其本征负磁阻来源于安德森局域化和自旋玻璃态的双重贡献，为发展磁场耦合优化热电性能的新策略提供了有意义的指导；发现低温热电材料CsBi4Te6表面自发形成的一维弗伦克尔缺陷，揭示了其自发形成的一维链缺陷及自发电子掺杂之间的关系，为理解热电材料电学性质并进一步指导合成高效的热电材料提供了电子结构数据支持；设计合成了一种具有寄生铁磁行为的二维超薄半导体Mn2P2S6，为发展磁场耦合优化热电性能的新策略提供了有意义的指导；设计合成了具有超低晶格热导率的(Bi2)m(Bi2Te3)n系列超晶格，发现了由多重机制导致的本征低热导率，不仅使(Bi2)m(Bi2Te3)n超晶格成为未来热电应用的重要候选材料之一，而且还为设计高效热电转换材料提供了新的思路。以上相关工作超额完成项目任务书目标，共在Nat. Sci. Rev., J. Am. Chem. Soc., Angew. Chem. Int. Ed., Adv. Mater.等国际顶级刊物发表SCI论文15篇，申请专利3件，其中授权1件。项目执行期间，项目负责人获得中国科学院青年创新促进会优秀会员支持，共培养博士后2名，博士3名，硕士1名，学士3名。项目执行期间，参与组织国际国内相关学术会议3次，受邀参与相关学术会议并做学术报告13次。