基于half-Heusler热电材料的低损耗、高可靠异质界面构筑及服役性能研究

Half-Heusler-based thermoelectric power generation devices are showing great prospect in fields of radioisotope thermoelectric generators and recovery of waste industrial heat. However, element diffusion or reaction is likely to occur at the interface between half-Heusler and electrode, which could lead to losses in the thermoelectric efficiency. Moreover, the thermal stress caused by the difference of thermal expansion coefficient between p-type and n-type half-heusler will seriously affect the reliability of the device. Therefore, the present project will focus on the n-type ZrNiSn-based and p-type ZrCoSb-based half-Heusler compound and systematically study the interfacial regulation mechanism and structural design method of half-heusler-based thermoelectric devices. A novel heterogeneous interface structured by half-heusler/full-heusler/metal is developed. The mechanism of interfacial bonding and element diffusion/reaction behavior is revealed so as to develop a new method for bonded interfaces with low electrical resistance and thermal resistance. An adaptive connection layer is designed to improve the reliability. The service performance of half-heusler-based devices under the complex and real environment with multiple external fields coupling is carried out. The failure mechanism based on the functional attenuation and structural damage within the heterogeneous interfaces is revealed. These results will establish a new method for construting the heterogeneous interface with low losses and high reliability.

基于half-Heusler（HH）材料的热电发电器件在深空探测、工业余废热回收等领域具有重要的应用前景。然而，HH材料/电极界面处易发生元素扩散或反应，引发器件性能衰减；且冷热交替下由n型、p型HH材料热膨胀系数差异带来的热应力将严重影响器件的可靠性。本项目将围绕n型ZrNiSn基和p型ZrCoSb基HH化合物，系统研究异质界面调控机理和结构设计方法，通过创制“half-Heusler/full-Heusler/金属”结构新型异质界面，阐明界面结合机理及元素扩散/反应行为传质机制，建立低电阻、低热阻异质界面优化新方法；设计自适应连接层，改善器件服役可靠性；开展HH器件在动态温度场、应力场等多个外场耦合的复杂真实环境下的服役性能研究，揭示基于异质界面功能衰减和结构损伤的热电器件失效机理，建立half-Heusler器件中低损耗、高可靠的异质界面结构调控新方法。

近年来，半赫斯勒材料是热电材料领域研究的热点之一。该类材料具有高使用温度、高热电性能、低廉的成本、优异的机械性能、良好的热稳定性等优点，是最具规模化应用潜力的热电材料之一。但是半赫斯勒材料批量制备工艺、器件界面阻挡层和器件设计研究工作较少，导致目前基于该类材料开发的热电发电器件的输出性能仅达到理论计算值的60%左右，仍有较大提升空间。因此，本项目以开发高性能半赫斯勒热电器件为目标，对包括原材料批量制备、器件界面阻挡层设计、高性能热电器件的设计开发全链条工艺技术及相应的应用科学问题进行了研究。取得的主要创新成果如下：.1.自蔓延批量合成HH材料 .采用自蔓延合成技术实现了半赫斯勒材料的百克级制备，它们的性能与悬浮熔炼法制备的同组份材料的性能相当。.2.界面阻挡层高温服役特性.开发了Cr、Mo作为ZrNiSn基和ZrCoSb基器件的新型阻挡层材料。对Cr、Mo与ZrNiSn基和ZrCoSb基的结合界面进行了微结构精细表征、反应热力学计算、界面电阻率测试。结果表明Cr/Mo作为阻挡层时界面结合良好，电输运性能和热稳定性极佳。.3.利用批量制备的半赫斯勒材料和开发的界面阻挡层材料，开展了单段半赫斯勒热电器件和双段半赫斯勒/碲化铋器件的研究。.对器件进行结构设计、优化和集成，开发的单段半赫斯勒和双段半赫斯勒+碲化铋热电发电器件最大转换效率分别达到11.1%和13.3%。