Mg2Sn-Mg3Sb2复合材料的异质晶界构筑与热电性能优化研究

In this proposal, the research topic is the thermoelectric performance boost of Mg2Sn-Mg3Sb2 composites by tailoring the dominant Mg2Sn/Mg3Sb2 heterogeneous grain boundaries (GBs). The strategies, including the fabrication process optimization, elements doping and 2D materials modifying, will be used for changing the microstructure of the heterogeneous GBs and increasing the interface thermal resistance, and hence obtaining the low thermal conductivity. On the other hand, the band convergence and d-orbital electrons will be used to adjust the band structures of Mg2Sn and Mg3Sb2, respectively. At the same time, the modulation doping will be applied to regulate the Fermi energy of Mg2Sn and Mg3Sb2 phase. Consequently, the energy barrier could be controllable for selectively scattering the low-energy carrier and hence enhancing the Seebeck coefficient. A new composite, characterized with the dominant “phonon damping and energy barrier optimization” heterogeneous GBs, could be obtained through the combining strategy of microstructure tuning and energy barrier optimization of GBs, which could become one of the directions for designing new thermoelectric materials. Finally, it is expected to obtain the new heterogeneous-GBs composite Mg2Sn-Mg3Sb2, with high thermoelectric figure-of-merit (ZT>1.5) and strong mechanical toughness.

本项目选取Mg2Sn-Mg3Sb2复合材料作为研究对象，并围绕高比例的Mg2Sn/Mg3Sb2异质晶界调控复合材料电声输运性能的科学问题展开。本项目拟通过工艺调控、元素掺杂和低维材料修饰的手段，调控Mg2Sn/Mg3Sb2异质晶界的微观组织结构和界面热阻，获取具有低热导率的Mg2Sn-Mg3Sb2热电复合材料；通过能带会聚效应和过渡金属d-轨道电子，分别调整Mg2Sn相和Mg3Sb2相的能带结构，并结合调制掺杂手段，改变Mg2Sn/Mg3Sb2异质晶界的界面势垒，实现对低能量电子的选择性散射，获取高的塞贝克系数；结合异质晶界微观组织和界面势垒的协同优化，获取具有“声子阻尼-电子过滤”特征晶界的新型热电复合材料，并归纳总结出设计新型热电复合材料的普适性方法。本项目的实施有望获取兼顾优异热电性能（ZT > 1.5）和力学性能的高比例异质晶界复合材料Mg2Sn-Mg3Sb2。

本项目选取Mg2Sn-Mg3Sb2复合材料作为研究对象，并围绕高比例的Mg2Sn/Mg3Sb2异质晶界调控复合材料电声输运性能的科学问题展开。本项目利用Janus纳米相中的异质界面对Mg3Sb2基热电材料的调控热导率，最终Mg3Sb1.5Bi0.5/Mg2Ge材料的室温ZT值达到0.6，在500 度时ZT值高达1.6。通过置换原子Te掺杂和间隙原子Mn掺杂，提高Mg3Sb2-xBix的室温功率因子和ZT值。利用自补偿掺杂优化Mg2-δSn热电材料的热电性能，同时结合晶格无序降低Mg2-δ-ySn1-xM固溶体热导率，通过复合高含量的Mg3Sb2的Mg2Sn基纳米复合材料Mg3Sb2，利用具有分形结构的异质界面Kapitza热阻降低晶格热导率。同时，我们还借助机器学习开展了新型室温热电材料快速筛选研究工作，发现Sb2TeSeS、Sb2S2Te、SbFeTe3等有潜力的新型室温热电材料如。最后，针对可穿戴室温热电器件开展了自供能应用研究，预测了不同拓扑结构的电极对热电发电输出功率的增益效果，掌握了最优的柔性热电器件电极结构。