Thermoelectric Properties of Ba_2-EuZnSb₂, a Zintl Phase with One-Dimensional Covalent Chains

The compound Ba₂ZnSb₂ has been predicted to be a promising thermoelectric material, potentially achieving zT > 2 at 900 K due to its one-dimensional chains of edge-shared [ZnSb_4/2]^4- tetrahedra and interspersed Ba cations. However, the high air sensitivity of this material makes it difficult to measure its thermoelectric properties. In this work, isovalent substitution of Eu for Ba was carried out to make Ba_2-EuZnSb₂ in order to improve the stability of the material in air and to allow characterization of thermal and electronic properties of three different compositions (x = 0.2, 0.3, and 0.4). Polycrystalline samples were synthesized using binary precursors via ball milling and annealing, and their thermoelectric properties were measured. Samples showed low thermal conductivity (<0.8 W/m K), a high Seebeck coefficient (350-550 μV/K), and high charge carrier mobility (20-35 cm²/V) from 300 to 500 K, consistent with predictions of high thermoelectric efficiency. Evaluation of the thermoelectric quality factor suggests that a higher zT can be attained if the carrier concentration can be increased via doping.