Synergistic Cu Doping and Yb Alloying Enhance Thermoelectric Performance of p-Type Mg _1.8 Zn _1.2 Sb ₂ -Based Material toward High-Efficiency All-Mg ₃ Sb ₂ Devices

High Resolution Image Download MS PowerPoint Slide AB 2 Sb 2 -type Zintl phases, particularly Mg 3 Sb 2 -based materials, have recently garnered significant attention owing to their earth-abundant, nontoxic constituents and excellent n -type thermoelectric (TE) performance in the medium temperature range. However, achieving high-performance all Mg 3 Sb 2 -based TE devices remains difficult due to the lack of a compatible and efficient p -type counterpart. Herein, a combined approach of Cu doping and Yb alloying is employed to synergistically optimize the carrier concentration, carrier mobility, and reduce lattice thermal conductivity, thereby achieving a high-performance p -type Mg 3 Sb 2 TE material. Consequently, a high zT value of 0.95 is obtained for the optimized composition Mg 1.18 Cu 0.02 Zn 1.2 Yb 0.6 Sb 2 at 673 K. To demonstrate practical applicability, a fully compatible Mg 3 Sb 2 -based TE device is fabricated using cupronickel as a common diffusion barrier for both p- and n -type legs, ensuring excellent interfacial stability and device reliability. A crack-free interface with a specific contact resistivity of ρ c ∼ 2.76 μΩcm 2 is achieved. The single-leg p-type device exhibited a maximum efficiency, η max ∼ 5.5%, while for a two-pair TE device, η max ∼ 9.2% at a temperature difference (Δ T ) of 374 K is realized. These findings demonstrate the potential of compositional engineering for developing efficient p -type Mg 3 Sb 2 materials and fully integrated TE devices for waste heat recovery.