(□,Ce)(Co,Fe)4Sb12方钴矿热电材料体系的相平衡与相稳定性研究

Ceδ(Co,Fe)4Sb12 Skutterudite thermoelectric material possesses the coupled effects by filling Ce atoms in the cage-like intrinsic crystal voids and by substituting Fe atoms for Co in the framework sites. Through filling and substitution, the electrical and the thermal transport properties can be optimized simultaneously, and the lattice thermal conductivity can be reduced dramatically. In addition, both the n-type and the p-type materials can be obtained in the same material system. Ceδ(Co,Fe)4Sb12 Skutterudite can be considered as the solid solution of the fully filled CeFe4Sb12 and the unfilled □Co4Sb12 compounds (where □ is the cage site). In the present project, the investigation interests are concentrated on the temperature-composition space for the stable existence of the (□,Ce)(Co,Fe)4Sb12 compound solid solution, the phase equilibria and the phase constituents of the alloys with different compositions, the solid solubility limits of both the filling element Ce and the substitutional element Fe in the □Co4Sb12-CeFe4Sb12 system, and the possible region for the miscibility gap and the Spinodal decomposition. On the basis of the thermodynamic assessment and optimization, the thermodynamic database of the related system will be developed, to obtain the close correlation between the analysis of phase equilibria and the design of phase constituents. The further investigation is expected on the multi-component Skutterudite thermoelectric material (□,Ce,Yb)(Co,Fe,Ni)4Sb12 formed by double filling atoms Ce and Yb in the cage-like intrinsic crystal voids and double substituting atoms Fe and Ni for Co in the framework sites, to provide the experimental data and scientific basis for the related alloy design, microstructure control and process optimization.

Ceδ(Co,Fe)4Sb12方钴矿热电材料具有晶格孔洞填充和框架原子取代双重效应，可以认为是由□Co4Sb12和CeFe4Sb12形成的化合物固溶体（□为晶格孔洞位置）。通过填充和取代的组合优化，实现电子和声子输运的协同调控，显著降低晶格热导率，而且表现出由n型向p型的逐步过渡。本项目拟针对CoSb3基方钴矿热电材料，研究(□,Ce)(Co,Fe)4Sb12化合物固溶体稳定存在的温度－成分空间，以及不同合金成分时的相平衡与相组成；研究□Co4Sb12-CeFe4Sb12体系中填充元素Ce和代位元素Fe的溶解度极限，以及可能存在的溶解度间隙和Spinodal分解范围。通过热力学优化评估，构建相关体系热力学数据库，取得相平衡计算和相组成设计的紧密关联，进而为(□,Ce,Yb)(Co,Fe,Ni)4Sb12双填充双取代方钴矿热电材料的合金设计、组织控制和工艺优化提供实验数据和理论依据。

(Ce,Va)(Co,Fe)4Sb12方钴矿热电材料, 通过填充（如Ce填充晶格间隙）和置换（如Fe置换框架原子）的组合优化，可实现电子和声子输运的协同调控，降低晶格热导率、提高电子电导率、改善热电性能。因此，本项目研究的主体是Ce-Co-Fe-Sb四元系，在相平衡关系实验测定和热力学参数优化评估的基础上，构建热力学数据库，并向多元掺杂体系扩充。已很好地执行了原定计划，发表SCI期刊论文12篇和国际会议论文10篇。取得的重要结果如下：.（1）针对Sb/Ge单组元，根据描述凝聚态相和真实气体相压力修正因子的Murnaghan方程和逸度系数模型，在保证相平衡关系、热化学性质、热物理性质等数据自洽合理性的基础上，建立了高温高压Sb/Ge单组元热力学数据库。.（2）对于关键基础二元系Ce/Fe-Sb，开展了热力学函数的模型修正和重新评估。采用Kaptay模型描述Ce-Sb液相，避免了Ce-Fe-Sb液相溶解度间隙在超高温度下持续出现；采用统一的三亚点阵模型描述相同晶体结构的(FeSb)和(CoSb)，有助于相关三元系的优化评估。.（3）系统地研究了Ce-Co-Sb、Ce-Fe-Sb、Co-Fe-Sb、Ce-Co-Fe三元系在等温等压和正常凝固条件下的相平衡关系和相转变过程。采用协调统一的热力学模型和参数，根据文献报道和本项目测定的相平衡与热化学实验数据，优化并获取了自洽合理的热力学特征参数。.（4）针对(Ce,Sc,Yb,Va)(Co,Fe,Ni)4(Sb,Ge)12方钴矿热电材料体系中若干掺杂元素构成的二元系（Ni-Sc/Yb和Ce/Yb-Ge）进行了必要的实验补充、模型修正和热力学评估，为扩充多元掺杂方钴矿热电材料热力学数据库提供基础数据。.（5）综合Ce-Co-Fe-Sb四元系中二元和三元子系的热力学优化结果，进行模型的集成整合，构建了(Ce,Va)(Co,Fe)4Sb12方钴矿热电材料主体数据库。同时，添加气相组分热力学参数，模拟材料制备条件下气相分压对相平衡、相稳定性及热分解温度的影响。.（6）尝试Bi置换Sb得到CoBi3化合物以及稀土原子填充晶格间隙得到(A/B)Co4Sb12（A =La,Gd,Yb; B= Ho,Er,Dy）化合物，将第一性原理与半经典方程相结合，分析和优化采用置换和填充途径对塞贝克系数、电导率、热导率等相关热电性能的影响。