Ytterbium Silicide (YbSi2): A Promising Thermoelectric Material with a High Power Factor at Room Temperature

Metal silicide-based thermoelectric (TE) materials have attracted attention in the past two decades, because they are less toxic, with low production cost and high chemical stability. Here, we study the TE properties of ytterbium silicide YbSi2 with a specific layered structure and the mixed valence state of Yb2+ and Yb3+. YbSi2 exhibits large Seebeck coefficient, S, accompanied by high electrical conductivity, σ, leading to high power factor, S2σ, of 2.2 mW m−1 K−2 at room temperature, which is comparable to those of state-of-the-art TE materials such as Bi2Te3 and PbTe. Moreover, YbSi2 exhibits high Gruneisen parameter of 1.57, which leads to relatively low lattice thermal conductivity, κlat, of 3.0 W m−1 K−1 at room temperature. The present study reveals that YbSi2 can be a good candidate of TE materials working near room temperature.