Thermoelectric Properties of As-Based Zintl Compounds Ba 1-x K x Zn 2 As 2 .

As-based Zintl compounds Ba1-x Kx Zn2 As2 were prepared by solid-state reaction followed by hot pressing. Ba1-x Kx Zn2 As2 (x ≤ 0.02) crystallizes in the α-BaCu2 S2 -type structure (space group Pnma) upon cooling from 900 °C, whereas it crystallizes in the ThCr2 Si2 -type structure (space group I4/mmm) for x ≥ 0.04. The lattice thermal conductivities are almost equivalent for both crystal structures with relatively low values of 0.8-1.1 W/mK at 773 K. The values are comparable to those of Sb-based Zintl compounds, though Ba1-x Kx Zn2 As2 consists of As atoms, which are lighter than Sb atoms. The electrical resistivity and Seebeck coefficient decreases with increasing x, indicating successful hole doping by K substitution. The dimensionless figure-of-merit ZT is 0.67 at 900 K for x = 0.02, opening a new class of thermoelectric materials with the As-based 122 Zintl compounds.