ZrSiCuAs型四元层状化合物的构建理论与电热输运性能调控

The strong coupling between electrical transport properties and thermal transport properties in thermoelectric materials limits the increase of thermoelectric figure of merit zT = S2σT/κ. Using the unique feature of natural superlattice structure in layered compounds to weaken the coupled effect, the independent adjustment of electrical and thermal transport properties can be realized in order to enhance the thermoelectric properties. In this project, conductive layers such as ACh (A = Cu, Ag; Ch = S, Se, Te) and BPn (B = Zn, Cd; Pn = As, Sb, Bi) as well as insulated layers such as AKF (AK = Ca, Sr, Ba) and REO (RE = La, Ce, Pr, Nd) are rationally stacked along c axis for building new ZrSiCuAs-type layered thermoelectric compounds AKFACh, AKFBPn, REOACh and REOBPn. The values of enthalpy and band-gap can be calculated by the first-principle high-throughput calculations to evaluate the stability and instinct thermoelectric properties. Subsequently, the pure samples of potential compounds are expected to be synthesized using traditional solid-state reaction method or high-pressure high-temperature method. The thermoelectric properties can be characterized to understand the structure-property relationship. Finally, the synergetic optimization for electrical and thermal transport properties would be carried out to obtain the high-performance thermoelectric materials (zT >1).

热电材料中电和热输运性能的耦合效应是限制热电优值(zT = S2σT/κ)提升的最关键因素。利用层状材料具有天然超晶格结构的特征可以弱化这种耦合效应，从而实现电性能与热性能近乎独立的调控来改善材料的热电优值。本项目拟选择导电功能层ACh(A = Cu, Ag; Ch = S, Se, Te)和BPn(B = Zn, Cd; Pn = As, Sb, Bi)与绝缘层AKF(AK = Ca, Sr, Ba)和REO(RE = La, Ce, Pr, Nd)进行搭配，构建新ZrCuSiAs型层状化合物AKFACh, AKFBPn, REOACh和REOBPn。通过第一性原理的高通量计算，预测不同组分的结构稳定性和本征热电性能。利用固相反应法或高温高压法对结构稳定化合物进行尝试合成并制备纯相的陶瓷样品以表征其电热输运性能，然后进行电和热输运性能的协同调控，以期获得热电优值大于1的潜在热电体系。

热电材料是一种能实现热能和电能直接相互转换的功能材料，在废热发电、电子制冷以及可穿戴电子设备供能等领域有重要的用途。热电材料能量转换效率由无量纲的热电优值zT（zT = S2σT/κ）决定，其中σ为电导率，S为塞贝克系数，κ为热导率，T为绝对温度。由于热电参数间强的耦合效应存在，通过单一调控某个参数实现热电优值的大幅增长十分困难。利用层状材料和笼状材料天然具有相对独立的电荷与声子输运通道特征可以弱化这种强耦合效应，从而实现电性能与热性能近乎独立的调控来改善材料的热电性能。本项目我们基于功能模块构建的理念，设计合成了多种具有ZrCuSiAs型四元层状化合物以及其它类型的层状化合物。在此基础上，发掘了多种高性能的笼状化合物材料。通过载流子浓度优化、能带调控以及全尺度声子散射等途径，进一步提升了体系的热电性能，获得了最高热电优值超过1的三种体系。该项目的顺利开展不仅挖掘了新的高性能热电研究体系，而且有助于开发新的电热输运解耦路径。在本项目支持下，共发表SCI论文16篇，申请发明专利四项。