高构型熵热电化合物设计和结构调控及电热输运机制研究

Either increasing the band valley degeneracy or decreasing the lattice thermal conductivity could be an effective strategy for optimizing the performance of thermoelectric (TE) materials. It is possible that both electrical and thermal transport properties can be synergistically optimized through increasing the band valley degeneracy and decreasing the lattice thermal conductivity in a semiconducting material system with a high configuration entropy. In addition, the high-entropy semiconducting materials could also possess excellent mechanical properties and high thermal stability. This project aims to develop high-entropy TE materials with high TE performance and good stability, which will lay a foundation for their commercial applications. The project will focus on the following challenges to reach the above goal: (I) the possibility of achieving high configuration entropy in TE materials; (II) the design and preparation of novel high-entropy TE materials with multi-elements in both anionic and cationic sites; (III) the prediction of the phase and crystal structure of the designed materials; (IV) developing new methods for the preparation along with the structure manipulation of high-entropy TE materials; (V) the discovery of physical correlations among the material entropy, TE properties and high thermal stability of high-entropy TE materials. This research will provide a new idea and approach for optimizing the properties of TE materials and enrich the theoretical framework and synthesis technology of the high entropy alloys.

提高热电半导体材料能谷简并度或降低晶格热导率均能有效优化材料的热电性能。具有高构型熵的热电半导体材料有可能在一个材料体系中同时实现能谷简并度的提高和晶格热导率的降低，实现电热输运的协同调控，大幅度提高材料的热电性能，并可能使体系具有高熵合金材料的优异力学性能和高温稳定性。本项目将探索热电半导体材料结构高熵化的可能性，设计和构建热电半导体材料阴离子位及阳离子位均为多主元的高熵热电半导体材料新体系，预测其物相及晶体结构，探索高熵热电半导体材料制备与结构调控新技术，揭示熵与半导体材料电热输运性质和稳定性之间的关系和规律，开发出具有高热电性能和高稳定性的高熵热电半导体材料，为其商业应用奠定基础。本项目的研究将为热电材料性能优化提供一条全新的思路和途径，也将丰富高熵合金的理论体系和制备技术。

本项目重点以岩盐相结构BiAgSeS、AgSbSe2及类金刚石结构CuCdInSe3等几种典型的热电材料体系为研究对象。构建了阴离子位及阳离子位均为多主元的高熵材料新体系，探索了材料制备与结构调控技术，进一步揭示了构型熵与材料电热输运性质和稳定性之间的关系和规律。取得的重要成果概述如下。.（1）采用自蔓延燃烧合成（SHS）技术在14s内即可快速制备得到BiAgSeS基高构型熵热电材料。快速非平衡过程将会在BiAgSeS材料中引入大量的纳米及原子尺度缺陷，这些缺陷结构在晶粒生长过程中提供了永不消逝的台阶源。在接下来的材料致密化过程中，台阶源继续主导晶粒生长，最终在晶界处留下纳米孔洞。增强的声子散射效应将降低材料的晶格热导率。最终块体材料的热电优值ZT得到显著优化，在773 K时取得0.5。.（2）在300 MPa烧结压力下，CuCdInSe3高构型熵热电材料内部产生了高浓度的孪晶结构，禁带宽度由0.82 eV降低至0.58 eV，室温载流子浓度由1.46 × 1016 cm-3增大到3.54 × 1018 cm-3，提高约2个数量级；晶界有序性增强，载流子迁移率大幅度提高，在室温时高达271 cm2V-1s-1。强烈的声学声子散射使得晶格热导率在773 K时低至0.76 Wm-1K-1。最终CuCdInSe3高构型熵热电材料的ZT值在773 K时达到0.45。.（3）Mn固溶增强的合金化点缺陷散射使(AgSb)0.8Mn0.4Se2高构型熵热电化合物具有极低的晶格热导率，室温下为0.49 Wm-1K-1。结合大幅优化的电性能，(AgSb)0.8Mn0.4Se2化合物在673 K下获得最大ZT值0.62。进一步调控Mn和Sb的化学计量比优化载流子浓度后，Ag0.9Sb0.89Mn0.21Se2在673 K下取得最高ZT值0.77。.本项目在过去4年的实施期间已发表SCI论文16篇，获得授权专利3件，培养硕士生6名、博士生4名，圆满完成了研究任务。所取得的成果对进一步利用构型熵效应提升热电性能提供了重要指导。