Cu2X固溶化合物纳米-亚纳尺度的结构化学和反Hume-Rothery现象及其关联电-热输运性质

固溶是提高热电性能的一个非常有效的手段，通过固溶可以增加结构的混乱度以增强声子散射降低热导。阴离子固溶的Cu2X (X=S, Se, Te)硫族化合物可获得高达2.1-2.3的热电优值，同时表现出丰富的特征纳米结构甚至异常的固溶现象，然而这些微观结构的形成原因以及与声子和电子输运特性的关联尚不清楚，限制了热电性能的进一步调控和优化。本申请项目主要利用原子分辨球差校正电镜及其辅助高性能能谱技术，以Cu2X基热电固溶体为主要研究对象，深入研究新发现的离子半径巨大差异的S和Te实现固溶的反Hume-Rothery现象，探讨阴离子和阳离子亚晶格的构筑方式和热力学稳定机制，分析纳米-亚纳尺度下的元素波动和结构涨落及其与固溶配比和晶体结构的内在关系，最终确立新型反Hume-Rothery固溶结构的构筑原则，探讨结构和微结构与材料电-热输运性能的关联，为新型高性能热电固溶体的设计和性能优化提供科学依据。

Forming solid solution has been confirmed to be an effective way to enhance the thermoelectric properties via introducing structural chaos to increase phonon scattering and decrease lattice thermal conductivity. Solid solutions of Cu2X (X=S, Se, Te) chalcogenides have shown outstanding thermoelectric performance with figure of merit zT up to 2.1-2.3. The solid solutions exhibit special nanostructures and abnormal solid solution phenomenon. However, the formation mechanism and effects on phonon and electron transports of these structural features remain unclear, which limits the further optimization of the thermoelectric properties. In this project, we will use mainly the atom-resolved aberration corrected transmission electron microscope along with advanced spectroscopies and in-situ techniques to investigate key structural issues in Cu2X (X=S, Se, Te) thermoelectric solid solutions, especially those of anti-Hume-Rothery rules, i.e. newly observed miscibility of S and Te with large mismatch in ionic radius. Researches will focus on the solid solution structures including configuration of both cation and anion sublattice, thermodynamic stability, and compositional and structural oscillation in nano and subnano scales. The researches are finally expected to establish the construction rules for novel compound solid solutions of anti-Hume-Rothery rules and relationships between crystal structures/nanostructures and thermoelectric properties in Cu2X solid solutions. The research results will provide scientific guidance for design and property improvement of high performance thermoelectric solid solutions.