金属掺杂对MxPb1-xTe(M=Sn,Mn,Ga,Ag等)单晶热电材料各向异性的调控及电声输运本征特性研究

One of core contents is to develop high-performance PbTe-based thermoelectric materials in thermoelectric research community. As for PbTe system, it has face-centered cubic structure with high melting point and large band gap. So far, thermoelectric studies are mainly focused on metal-doped PbTe polycrystal system. However, considering the unessential factors such as grain boundary, defects, etc., it seriously hinders the understanding of intrinsic characteristics of isotropy and electron and phonon transport. Therefore, it is urgent to develop the Macro fabrication technique of large-sized PbTe single crystals, which is the key factor for commercial applications. In this project, we will utilize the vertical Bridgeman method to fabricate a series of MxPb1-xTe (M=Sn, Mn, Ga, Ag, etc.) single crystals by different metal doping at Pb sites. Furthermore, we will modulate and optimize carrier concentration and band structure. Combined with theoretical and experimental results, we will study the essential mechanism of isotropy and anisotropy of metal-doped PbTe single crystals, and obtain the basic physical parameters of electron and phonon transport along different measured orientations. All of results will reveal the interaction among doped metal, Pb, and Te atoms, and intrinsic mechanism between dominant carrier and phonon scattering. Ultimately, we will establish the association among microstructure, electron-phonon transport mechanism, anisotropy, and thermoelectric performance, which provides new idea for the design and development of high efficient thermoelectric materials.

开发高性能PbTe基热电材料是热电学界研究的核心内容之一。PbTe属于面心立方结构，其熔点高、禁带宽度大，适用于中温区热电发电领域。目前热电研究主要集中在金属掺杂PbTe多晶体系，然而由于晶界、缺陷等非本征因素的影响，严重阻碍了对其各向同性和电声输运特性的理解。因此，亟需开发大尺寸PbTe基单晶的宏量制备技术，这是实现商业化应用的关键因素。本项目拟通过Pb位掺杂不同金属元素，利用垂直Bridgman法合成MxPb1-xTe(M=Sn,Mn,Ga,Ag等)系列单晶，调控和优化载流子浓度及能带结构，并结合理论与实验结果，研究金属掺杂前后PbTe单晶各向同性和各向异性的本质机理，获取不同取向上电声输运的基本物理参数，揭示金属原子与Pb、Te原子的相互作用关系、以及主导载流子与声子散射的内在机制，建立微结构、电声输运机制、各向异性与热电性能之间的关联，为设计和开发高效热电材料提供新思路。

开发高效PbTe热电材料是国际热电领域研究的核心内容之一，尤其性能相匹配的p型和n型PbTe热电材料是实现中温区商业化应用的关键。目前，p型PbTe材料热电性能较高，但n型材料仍相对较低。鉴于此，本项目重点研究了n型PbTe热电材料中的金属动态掺杂、能量过滤效应、共振能级、能带调控、有效质量工程、低固溶度效应、多相工程、多尺度缺陷、合金化效应等一系列热电性能增强策略，热电优值最高可达1.5以上，并结合理论与实验结果，有效揭示主导载流子与声子散射的本征机理，成功建立了微结构、电声输运机制、热电性能之间的关联。此外，本项目还系统对比研究了SnTe、GeTe、(SnS)1.2(TiS2)2、AgCrSe2、Bi2Te3、CdSb、Ba8Ga16Ge30、Cu2Te等不同体系的热电材料，为制备高效热电材料与新型器件提供重要支撑。本项目发表标注基金资助的SCI论文37篇，其中第一作者和通讯作者36篇，包括Nano Energy、Journal of Materials Chemistry A、Chemical Engineering Journal、Materials Today Physics、Energy Conversion and Management、ACS Applied Materials & Interfaces、Journal of Materials Science & Technology、Applied Physics Letters等，其中影响因子大于17的1篇，大于13的1篇，大于12的2篇，大于9的14篇，大于8的1篇，Nature Index 6 篇，授权国内发明专利6项，申请国内发明专利2项，圆满完成项目预期指标和各项任务，取得了较为优秀的研究成果。本项目对加强我国在热电材料领域的国际竞争力，获取自主知识产权和实现能源高效利用都具有重要的现实意义。