High-Temperature Thermoelectric Properties of Polycrystalline Silicon Clathrate Ba 8 TM x Si 46− x (TM = Ni, Pt)

The n -/ p -type stability of a silicon clathrate in which silicon was substituted with nickel or platinum was evaluated by density functional theory calculations. Then, Ba 8 Pt 5 Si 41 and Ba 8 Pt 1.5 Ni 3.5 Si 41 were synthesized, and their thermoelectric properties were investigated. The polycrystalline compounds, which have a type-I clathrate structure, were prepared through arc melting and spark-plasma-sintering. The crystal structures and elemental compositions of the synthesized samples were characterized via powder x-ray diffraction and electron microprobe analyses, respectively. The temperature dependence of both the electrical resistivity and the Seebeck coefficient was measured.