Study on control of guest-host interactions and thermoelectric properties in clathrate semiconductors

用铕在客体位置部分取代钡，制备了新型硅包合物——热电半导体。发现铕客体优先占据晶体结构空隙中的2a位。铕取代对电子结构有显著的影响，由于选择有效质量的增加，导致塞贝克系数的增强。此外，由于在2a位点上客体原子的爱因斯坦温度降低，声子的“咔嗒”散射（共振散射）增强，铕取代引起晶格热导率的显著降低。

New silicon clathrates, thermoelectric semiconductors, were developed by partial substitution of europium for barium on guest sites. The europium guest was found to occupy preferentially the crystallographic position 2a site in the voids in the crystal structure. The europium substitution had a significant influence on the electronic structure, resulting in an enhancement of the Seebeck coefficient due to an increased election effective mass. Further, the europium substitution caused a marked reduction in the lattice thermal conductivity due to an enhanced “rattling” scattering (resonant scattering) of phonons because the Einstein temperature of the guest atoms on the 2a site was reduced.