基于原子力显微技术的低维硫/氧化物热电材料的输运机制研究

Low-dimensional thermoelectric materials can increase the thermal conductivity by using of numerous surfaces and interfaces to scatter phonons more effectively than electrons, and raise the Seebeck coefficient by increasing the density of electronic states near the Fermi level, then enhance the dimensionless figure of merit and energy conversion efficiency. They can be used in the future as a clean energy conversion technology for the harvesting of waste heat as well as for converting solar energy into useful electricity. The goal of this project is to synthesize a serial of nanocrystal thermoelectric sulfide and oxide nanofibers with different component, size and structure by hydrothermal and improved electrospinning methods, respectively. Novel scanning thermal microscopy (SThM) and Kelvin probe force microscopy (KPFM) will be used to do in situ measurement on the surface of the nanostructure thermoelectric materials. Finite-element method (FEM) modeling technique will be used to evaluate the temperature and electric field distribution of the different nanostructure materials contact with the probe. Combining the results of the simulation with the in situ measurement we can quantitative characterization the Seebeck coefficient, electrical conductivity, thermal conductivity, and carrier density distribution of the low-dimensional sulfide/oxide thermoelectric materials. These microscopic thermoelectric transport parameters will be compared with the macroscopic performance of bulk materials with spark plasma sintering, then the relationship between the microstructure, microscopic transport and macroscopic thermoelectric performance will be established.

低维热电纳米材料能够通过比电子更有效地利用表面和界面的声子散射，大幅度降低材料的热导率，同时通过引起费米能级附近的态密度增加，实现塞贝克系数的增加，从而提高材料的热电优值和能量转换效率。在废热利用和太阳能的有效采集利用方面都具有极大的应用前景。本项目将采用水热法和改进的静电纺丝法，合成一系列不同成分、尺寸和结构的低维硫/氧化物纳米晶热电材料。重点采用扫描热显微技术和开尔文探针力显微技术对不同纳米结构的材料进行原位实时测试，结合有限元数值模拟的温度场和电场分布，得到低维硫/氧化物纳米晶热电材料微观的塞贝克系数、电导率、热导率、载流子浓度等热电输运参数。将材料的微观热电输运参数与放电等离子烧结样品的宏观热电性能进行分析比较，建立低维硫/氧化物纳米材料结构、微观输运性和宏观热电性能之间的关联。

低维热电纳米材料能够通过比电子更有效地利用表面和界面的声子散射，大幅度降低材料的热导率，同时通过引起费米能级附近的态密度增加，实现塞贝克系数的增加，从而提高材料的热电优值和能量转换效率。本项目采用改进的静电纺丝法合成一系列不同成分、尺寸和结构的低维硫/氧化物纳米晶热电材料。重点采用扫描热显微技术和开尔文探针力显微技术对不同纳米结构的材料进行原位实时测试，并结合有限元数值模拟的温度场和电场分布，得到了低维硫/氧化物纳米晶热电材料微观的塞贝克系数、电导率、热导率、载流子浓度等热电输运参数。将材料的微观热电输运参数与宏观的热电性能进行分析比较，建立低维硫/氧化物纳米材料结构、微观输运性和宏观热电性能之间的关联。同时通过机器学习模型构建材料结构与热电耦合性能的关系，在该模型的指导下发现14%Nd掺杂BiCuSeO在923K时其ZT值达到1.05，是纯BiCuSeO材料ZT值的近2倍，为实验制备高性能热电材料提供了理论指导。