一维纳米碲化物的可控合成、生长机理及热电性能研究

Telluride thermoelectric material is one of important function material which can convert low-grade heat energy to high-grade electric energy. Thermoelectric device is difficult to apply for exhaust heat recycling during supply heating beacause of low thermoelectric properties. In order to improving thermoelectric properties, the crystal structure and morphology of tellurides are controlled systematically. In this foundation, one-dimensional nanostructure tellurides thermoectric materials are prepared by self-sacrificing method. The morphology of powder and bulk materials are controlled by microwave heating and spark plasma sintering (SPS) techniques, respectively. The crytal growth mechanism of one- dimensional nano materials is studied by high resolution transmission electron microscopy (HRTEM), atomic force microscope (AFM) techniques, etc. Combining with microwave electromagnetic theory, the mechanism of microwave action is also speculated. The crystal structure (bond length, bond angle, structural aberration etc) and electronic band structures (density of states, band structure etc) of the thermoelectric materials are studied using Rietveld refinement and the density functional theory (DFT). Combining with the test result of electric conductivity, Seebeck coefficient, thermal conductivity and Hall coefficient, the transport properties of carrier and phonon is given. Our work will provide the theoretical and experimental evidence for developing telluride thermoelectric materials with high performance and wide application.

碲化物热电材料是一类重要的热电转换功能材料，由其制作的温差发电器件可捕捉流失的低品位热能，并转化为高品位电能，如能将其用于北方居民供暖过程中的余热、废热回收，将节省大量煤炭的使用。制约热电器件实用化的主要瓶颈是材料的热电性能偏低。因此，本项目从材料的结构、形貌调控入手，通过材料纳米化、低维化提高其热电性能。在前期研究基础上，拟采用自牺牲模板法合成一维纳米碲化物热电材料；采用微波加热技术和SPS烧结技术分别调控材料粉体和块体形貌；采用高分辨透射电镜、原子力显微镜等测试手段研究一维纳米晶体的生长机理，结合电磁场理论揭示微波辐射对一维晶体生长的作用机制；利用Rietveld法和密度泛函理论研究材料的晶体结构（键长、键角、结构畸变等）和电子结构（态密度、Fermi能级等），结合热电性能和Hall系数测试结果，分析载流子、声子的输运性质，为高性能、可实用化热电材料的结构设计和合成奠定基础。

本项目采用微波辅助液相法，在可控条件下制备了具有特定形貌、组成、结构且性能优异的碲和碲化物热电材料，考查了不同条件对纳米粉体的形貌、结构和性能的影响。采用高分辨电镜、电子衍射等手段，研究了材料的微观结构形貌；利用电性能综合测试系统测试了材料的电导率、Seebeck系数，计算了材料的功率因子，分析了这些材料形貌-结构与电输运性能之间的关系。研究表明采用微波加热方式可以简单、快速（10-30min）合成碲化物纳米热电材料。这种高效、节能和环保的微波辅助合成技术为获得高性能纳米热电材料提供了借鉴。