Thermoelectric transport properties of the van der Waals-type layered rhombohedral SnAs-based compound, EuSn₂As₂

The thermoelectric transport properties of the van der Waals-type layered rhombohedral SnAs-based compound, EuSn2As2, have been investigated. A densified polycrystalline sample of EuSn2As2 with porosity (φ) of 2.4(9) vol.% exhibited a weak orientation to the c-axis for hexagonal coordination system; the weak orientation is parallel (P ∥) to the pressing direction of hot pressing. Measurements of electrical resistivity (ρ), Seebeck coefficient (S), and thermal conductivity (κ) were conducted perpendicular (P ⊥) to the pressing direction. The experimental values of ρ and S exhibit metallic temperature dependence and p-type carrier polarity. The power factor (P) was 0.51(8) mW m-1 K-2 at 673(4) K. Using the Wiedemann-Franz-Lorenz law, the phonon thermal conductivity (κ ph) was estimated to be 0.4(6) W m-1 K-1 at 673(6) K. The dimensionless figure of merit, ZT, was 0.092(17) at 673(3) K.