Transport Property in the Filled Skutterudite Structure

热电半导体热电转换技术的研究有望解决清洁能源供应充足、余热回收和微电子技术发展等现代问题。具有填充Skutterudite结构的RFE_4Sb_&lt；12&gt；体系化合物具有很大的载流子迁移率和多个声子散射中心，是下一代热电半导体的候选材料。通过X射线衍射实验、透射电子显微镜观察、能谱分析、塞贝克系数、电阻率、热导率、摩斯鲍尔效应和霍尔系数的测量，发现在一个晶胞中价电子总数为142-144的有限范围内，填充的方解石结构以不同的成分存在。随着第四元素在Fe位上数量的减少，稀土元素在空洞中的填充数增加。Sb环的晶格参数和形状依赖于Ce在空位中的填充数。塞贝克系数依赖于单位体积的价电子总数。通过添加第四元素或控制稀土元素在空穴中的填充量，可以改变材料的电阻率、导热系数、载流子密度、空穴迁移率、声子的散射频率，从而获得良好的功率因数、优良的品质因数。

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.