Ytterbium Silicide (YbSi2): A Promising Thermoelectric Material with a High Power Factor at Room Temperature (Phys. Status Solidi RRL 2/2018)

The so‐called power factor S2σ (with S the Seebeck coefficient and σ the electrical conductivity) determines the power generation performance of thermoelectric (TE) devices. Since S and σ have a trade‐off relationship as a function of carrier concentration, it has been difficult to enhance S2σ. Metal silicide‐based TE materials have attracted attention in the past two decades, because they are less toxic than conventional TE materials (such as Bi2Te3 and PbTe), involve low production cost and show high chemical stability. The study by Ken Kurosaki and co‐workers (see article no. 1700372) reveals that YbSi2 can be a good candidate of TE materials working near room temperature: Metallic YbSi2 has a specific layered structure and mixed valence state of Yb2+ and Yb3+, where Yb2+ is the major ionic component at low temperature, and the amount of Yb3+ increases with increasing temperature. This temperature‐dependent valence fluctuation would increase S with keeping high σ, which enables to enhance the power factor of YbSi2 to 2.2 mW m−1 K−2 which is comparable to that of Bi2Te3 in the wide temperature range from room temperature to 523 K.