强磁场下制备晶粒择优取向的SnSe纳米材料及其热电性能研究

SnSe polycrystalline materials have great potential for thermoelectric application due to their simple manufacturing technical, low preparation cost and stable mechanical properties. Nanostructures can depress enhancement of electrical conductivity and power factor by enhanced grain boundary scattering. How to effectively improve power factor of nanostructured materials remains a key challenge. High magnetic field has the ability to impose grains preferred orientation on a material. In this project, we propose that electrical conductivity and power factor in SnSe nanostructured materials can be improved by applying high magnetic field to produce grain preferred orientation. Moreover, nanostructures obtained by in-situ hydrothermal process in high magnetic field significantly diminish lattice thermal conductivity. It is expected that the electrical and thermal transport properties in SnSe nanostructured materials can be synergistically optimized. We can reveal the manipulating mechanism of high magnetic field on microstructures and degree of orientation by investigating its effects on microstructures and degree of orientation. We fabricate SnSe nanostructured materials with grain preferred orientation. By studying the effects of degree of orientation on thermoelectric properties of SnSe nanostructured materials, we can disclose the change mechanism of thermoelectric properties inducing by grain preferred orientation. In the meanwhile, we can demonstrate the influence mechanism of hole doping on thermoelectric properties of SnSe nanostructured materials with grain preferred orientation. And the effective ways for optimizing thermoelectric properties of thermoelectric materials by high magnetic field will be disclosed by this project. This project will provide theoretical guidance for research and development of high performance SnSe polycrystalline material. This study opens a new pathway for broadening and designing prospective thermoelectric materials.

SnSe多晶热电材料具有制备工艺简单，生产成本低，机械性能稳定等突出优点，具有广阔应用前景。由于纳米材料中大量的晶界散射会抑制材料电导率和功率因子的提高，现有方法提升功率因子幅度不够。为解决SnSe纳米材料功率因子不高的问题，由于强磁场能使晶粒择优取向，项目提出借助强磁场诱导SnSe纳米材料的晶粒择优取向提升其电导率和功率因子，强磁场原位水热合成得到的纳米结构能有效降低材料晶格热导率，有望实现协同优化材料的电声输运。系统研究强磁场对SnSe纳米材料显微结构和取向度的影响，揭示强磁场对材料显微结构和取向度的调控机制；构筑晶粒择优取向SnSe纳米材料，研究取向度对材料热电性能的影响，揭示晶粒择优取向引起材料热电性能变化机制；研究空穴掺杂对晶粒择优取向SnSe纳米材料热电性能的影响，探索出利用强磁场优化材料热电性能的有效途径，为高性能多晶SnSe研发提供理论指导，为热电材料性能优化提供新思路。

SnSe多晶热电材料具有制备工艺简单，生产成本低，机械性能稳定等突出优点，具有广阔应用前景。由于纳米材料中大量的晶界散射会抑制材料电导率和功率因子的提高，现有方法提升功率因子幅度不够。为解决SnSe纳米材料功率因子不高的问题，项目提出开展强磁场下制备晶粒择优取向的SnSe纳米材料及其热电性能研究。本项目研究揭示了强磁场对 SnSe 纳米材料显微结构和取向度的调控机制，以及材料显微结构引起材料热电性能和取向度变化机制；揭示了强磁场对空穴掺杂SnSe纳米材料热电性能的影响机制，探索出利用强磁场优化材料热电性能的有效途径；探明了不同掺杂对SnSe纳米材料热电性能的调控机制，提出了利用相分离和共格纳米结构协同调控；能带工程与共格纳米析出协同调控；电子自旋调控；空位工程等策略，探明了热电材料性能调控新机制，开发了优化热电材料性能的多种新方法，研制了高性能SnSe纳米热电材料。研究发现利用磁场辅助微结构调控提升热电材料性能，实现了磁场对材料微结构的有效调控，导致能量过滤效应和态密度增强，使得磁场下合成的Se量子点/Sn0.99Pb0.01Se纳米材料热电优值ZT在873 K时达到了2.0。通过强磁场在SnSe纳米材料中获得了大量位错、层错结构，导致材料中大的应力场波动，并与能量过滤效应协同优化，提升SnSe纳米材料电声输运性能，将ZT提升至1.9。进一步发现强磁场有效调控了Sn位空穴掺杂SnSe纳米材料的微观结构和热电性能，磁场下合成的空穴掺杂多晶SnSe的ZT由无磁场下制备的1.2提高到了1.89。这些研究说明利用稳态磁场调控热电材料微结构对于优化材料热电性能十分有效。研究了通过引入阳离子Sn空位，实现了对电热输运的协同调控优化，ZT达到2.1。利用相分离和共格纳米结构策略优化SnSe纳米材料热电性能，材料的ZT达到了2.2，通过本项目的实施大幅提升了该材料热电性能，为高性能多晶SnSe研发提供理论指导，为热电材料性能优化提供新思路。