IVA 族元素构成的笼状物热电材料晶体结构中，客体原子在主体多面体内作非简谐运动，因而对载热声子有强散射作用导致热导率急剧下降, 但对导电性能无显著影响，被认为是极具潜力的废热利用、无氟制冷的新型绿色环保功能材料。I型笼状热电材料表现出高热电性，但其晶体结构及热电机理仍需要进一步研究完善。本项目将利用Ge同位素效应，结合中子衍射、Raman、基本物性测量以及第一性原理理论计算，研究I型笼状物热电材料M8Ga16Ge30晶体结构及电子-声子相互作用对I型笼状物热电性质的影响。本研究不但能有效区别p-和n-Ba8Ga16Ge30 (BGG) 笼状物中Ga和Ge原子占位，还可以研究客体原子和主体多面体结构间的电声相互作用对其电性的影响，可望成为解决国际学术界存在长期争议的p-和n-BGG热导率上存在巨大差异的决定因素，将对于完善笼状物材料热电理论，设计高效热电材料具有非常重要的指导意义。

In IVA-group element constructed clathrate compounds, it is sugested that heat transfer is suppressed by phonon scattering, even though electric transport remains high in the Bloch lattice, which can give rise to high thermoelectric figure of merit. Therefore, it is regarded as a very promising new green functional material for enviroment protection. Type-I clathrate M8Ga16Ge30 show high thermoelectricity. However, their crystal structures and thermoelectric mechanism are not fully clarified and thus need to be further improved. In this proposal, the crystal structure and electron-phonon interaction of p/n-Ba8Ga16Ge30, n-Sr8Ga16Ge30 are investigated based on Ge isotope effect, using neutron scattering, Raman and physical property measurement system and etc, combined with first principle theoretical calculation. These investigation can not only effectively differentiate Ga/Ge occupation in M8Ga16Ge30 crystals, but also clarify the electron-phonon interaction between guest atom and host fromework, and thus resolve the long-debated question about the thermal conductivity difference between p- and n-Ba8Ga16Ge30. This will be very significant to improve thermoelectric mechanism for clathrate compounds, and will provide guidance to design high-performance thermoelectric materials.