基于制备多尺度微结构调控SnSe复合材料热电性能

SnSe single crystal is well known as a promising thermoelectric material, while the application of which is limited due to its only exhibiting extraordinary thermoelectric properties along the b-axis. Therefore, the development of polycrystalline SnSe with a high ZT becomes the main focus for the researchers. To promote the thermoelectric properties of polycrystalline SnSe, a probably way is to prepare SnSe based thermoelectric material with multi-scale microstructure via element doping and high temperature sintering. However, the precipitation of doping elements caused by grinding heat always leads to a significant decrease of the thermoelectric properties of SnSe. Thus, there are still great technical problems in the preparation of high quality ultrafine SnSe based powders.. In summary based on above problems, ultra-low temperature (the temperature of liquid nitrogen) grinding is proposed to prepare ultrafine SnSe powders with different particle sizes in this project. By introducing low dimensional nanomaterials, the grain size and orientation of SnSe is controlled delicately on the sintering process. Heterogeneous interface is constructed at the grain boundaries due to the existence of nanophases, which enhances phonon scattering due to the energy filtering effect, resulting in the significantly improvement of the thermoelectric properties of SnSe. Therefore, an efficient method is proposed to prepare the SnSe based materials with high performance, which will promote the further development of preparation technology and theory, and accelerate their application process.

SnSe单晶材料展现了极为优异的热电性能，但是只在b轴方向具有极高的热电性能，严重限制了其制备热电器件走向实际应用，因此制备高性能的多晶SnSe热电材料已成为当前的研究热点。为了提高多晶SnSe材料的热电性能，采用元素掺杂同时通过烧结技术制备出具有多尺度微结构SnSe基热电材料是一条可行的途径。但是在粉碎过程中由于产生热效应导致掺杂元素析出，严重劣化了SnSe材料的热电性能，所以高质量超细SnSe基粉体制备仍然存在着技术上的难题。. 针对上述问题，本项目提出采用超低温研磨技术（液氮温度）制备不同粒径超细SnSe粉体，通过引入低维纳米材料，在烧结过程调控SnSe晶粒尺寸和取向。利用纳米相在其晶界构筑异质界面，实现能量过滤效应，增强声子散射，从而实现热电性能的大幅提高。通过本项目的研究，发展一种制备高性能SnSe基材料的可行途径，推进制备技术及理论的发展和应用进程。

SnSe单晶材料展现了极为优异的热电性能，但是只在b轴方向具有极高的热电性能，严重限制了其制备热电器件走向实际应用，因此制备高性能的多晶SnSe热电材料已成为当前的研究热点。为了提高多晶SnSe材料的热电性能，采用元素掺杂同时通过烧结技术制备出具有多尺度微结构SnSe基热电材料是一条可行的途径。但是在粉碎过程中由于产生热效应导致掺杂元素析出，严重劣化了SnSe材料的热电性能，所以高质量超细SnSe基粉体制备仍然存在着技术上的难题。本项目通过掺杂不同元素，如Na、Ag和Te，对多晶SnSe的能带结构进行调控，使载流子浓度最佳；同时，结合低温冷冻研磨技术制备的超细粉体，通过引入多种低维纳米材料，如CNTs、rGO等，在烧结过程调控SnSe晶粒尺寸和取向，制备出具有多尺度结构且性能优异的SnSe基热电材料。利用低维纳米材料在SnSe晶界处构筑异质界面，实现了能量过滤效应，增强了声子散射，从而实现了热电性能的大幅提高。通过本项目的研究，成功建立了具有多尺度结构且性能优异SnSe基热电材料的制备技术路线，也为制备其它高性能热电材料探索了一条可行的新途径。