新型热电化合物的制备和研究对解决能源短缺和环境污染具有重要的科学意义。本申请项目拟以I型Li-Ge基clathrate热电化合物为研究对象，理论与实验相结合，在对化合物进行合理设计的基础上，优化合成方法，实现化合物的可控制备。探索clathrate物相形成机制，研究化学组成对晶体结构的影响，研究替换缺陷和空位缺陷的产生条件、缺陷有序性变化规律、原结构与超结构之间的转变过程，进而研究由此引起的电子结构重组机制和对化合物热、电等物理性能的影响。明确Li在框架位置上的行为特点以及Li原子特性对化合物晶体结构、物理性能产生的特殊效应和机理，深入理解组成－结构－成键－性能之间的内在关系。以此为指导，通过调节化学组成和晶体结构，优化化合物的热电性能，获得性能优良的潜在热电材料。本申请项目的研究将进一步扩展热电化合物的研究领域，为化合物热电性能的优化提供依据。

The research of new thermoelectric materials has important scientific significance on solving the problem of energy shortage and environmental pollution. This project is to design, synthesize and characterize new thermoelectric clathrate-I compounds with Li-Ge framework. Based on theoretical knowledge and experimental experience, the compounds will be synthesized under control by applying reasonable techniques. The adjustable chemical compositions of clathrate compounds at different temperatures will be determined. The crystal structure of compounds with different chemical compositions will be studied. The order of defect positions, phase transition between original structure and superstructure, complex interrelations of Li substitution and vacancy formation in the framework structure will be investigated and analysized. As a direct and efficient approach, the in-depth understanding of the composition - structure - bonding - property relationship, which serves as basis of the rational design is also part of the objective absorbed within the scope. Therefore, the compositions, crystal structures, electronic properties and physical properties of compounds and their relations will be characterized and concluded. In particular, the characteristic behavior of Li atoms in the framework positions, as well as the influence on crystal structure and physical properties will be studied, in order to provide scientific basis for the controllable modulation of performance on clathrate compounds and further to find new thermoelectric materials. The proposed research will expand the area of thermoelectric compounds, the basis for the design and synthesis will largely attribute to the new development of the intermetallic chemistry and physics. In addition, the characteristics of Li atoms in the crystal structure and physical properties will provide new directions on optimizing the thermoelectric properties of clathrate compounds.