Enhanced thermoelectric properties of BaZn2Sb2via a synergistic optimization strategy using co-doped Na and Sr

Abstract

Due to rich structural features and promising thermoelectric performances, antimony-based Zintl compounds, such as AZn₂Sb₂ (A = alkaline earth elements or divalent rare earth elements), have attracted much attention for both fundamental analysis and thermoelectric applications. Polycrystalline samples of Ba_1−x−yNa_xSr_yZn₂Sb₂ (0 ≤ x ≤ 0.1, 0 ≤ y ≤ 0.1) were prepared by a solid-state reaction method and hot press sintering with the aim of achieving synergistic optimization of the power factor and thermal conductivity. Substitution of Ba by Na could achieve optimization of the carrier concentration, leading to an increase in the power factor to 10.46 μW cm⁻¹ K⁻² at 704 K for Ba_0.94Na_0.06Zn₂Sb₂ in comparison to pristine BaZn₂Sb₂ (5.39 μW cm⁻¹ K⁻² at 464 K). The introduction of Sr depressed the thermal conductivity by lattice disorder. Combining the two aforementioned effects, a higher ZT value of 0.58 at 704 K was obtained for Ba_0.92Na_0.06Sr_0.02Zn₂Sb₂, which is greater than that for BaZn₂Sb₂ by 87% at the same temperature.