Transport Property in the Filled Skutterudite Structure

高效将热能转化为电能的热电半导体研究有望解决清洁能源充足供应、废热回收和微电子技术发展等现代问题。RFe_4Sb_4<12>（R=稀土元素）系填充方钴矿结构的化合物由于具有很高的载流子迁移率和多个声子散射中心而被认为是下一代热电半导体的候选材料，本文研究了RFe_8Sb_4系填充方钴矿结构的热电性能、载流子和声子的输运机制<24>（R=稀土元素）通过X射线衍射实验、透射电子显微镜观察、EDX分析、塞贝克系数、电阻率、热导率的测量，填充的方钴矿结构在价电子总数142- 148的有限范围内以各种成分存在。144在一个单位细胞。随着第四种元素在Fe位上的数量减少，稀土元素在空洞中的填充数量增加。晶格常数和Sb环的形状取决于Ce在空洞中的填充数。塞贝克系数取决于每单位体积的价电子总数。通过添加第四种元素，或通过控制稀土元素在空穴中的填充数量，可以改变材料的电阻率、热导率、载流子密度、空穴迁移率、声子散射频率等，从而获得良好的功率因数、品质因数。

Researches on thermoelectric semiconductors with high efficiency to convert heat energy to electric energy are expected to solve modern problems such as sufficient supply of clean energy, waste heat recovery, and development of micro electron techniques. The compound of the RFe_4Sb_<12> system (R=rare earth element) with the filled skutterudite structure is a candidate for the next thermoelectric semiconductor, because it possesses both very large mobility of charge carriers and many scattering centers of phonons.This research investigated the filled skutterudite structure, the thermoelectric property, the transport mechanisms of charges carriers and phonons in the compound of the RFe_8Sb_<24> system (R=rare earth element) by means of X-ray diffraction experiments, transmission electron microscopic observations, EDX analyses, measurement of the Seebeck coefficient, electrical resistivity, thermal conductivity, moessbauer effect and the Hall coefficient.The filled skutterudite structure exists with various compositions in a limited range of valence electron total number 142-144 in a unit cell. The filling number of rare earth element in voids increases with decreasing the number of the forth element on Fe sites. The lattice parameter and the shape of Sb ring depend on the Ce filling number in voids. The Seebeck coefficient depends on valence electron total number per unit volume. By adding the forth element, or by controlling the filling number of rare earth element in voids, the electrical resistivity, the thermal conductivity, the carrier density, the hole mobility, the scattering frequency of phonons can be changed in order to get good power factor, the good figure of merit.