Thermoelectric Property Mapping for High‐Performance Integrated MgAgSb‐MgCuSb System

ABSTRACT To achieve high conversion efficiency in thermoelectric (TE) modules, not only thermoelectric materials (TEMs) with high figure‐of‐merit zT but also the optimization of thermoelectric interface materials (TEiMs) is required. For TEMs, enhancing zT relies on increasing power factor PF and lowering thermal conductivity κ , while for TEiMs, high electrical conductivity and κ are essential, which highlights the importance of the integrated design of TEMs and TEiMs. In this work, we select p‐type MgAgSb as the object and construct a TE property mapping of the integrated MgAgSb–MgCuSb two‐phase system by tuning the Ag/Cu ratio. Based on the thermoelectric property mapping, Ag‐rich compositions exhibit superior PF and zT values for TEM, maximized in PF∼21 µW cm −1 K −2 , zT = 1.12 for MgAg 0.97 Cu 0.03 Sb. Conversely, Cu‐rich composition MgAg 0.05 Cu 0.95 Sb is identified as the optimal TEiM for its low contact resistance and superior carrier and phonon transport properties, reducing energy loss. A two‐pair thermoelectric module integrated with n‐type Mg 3 (Sb, Bi) 2 is successfully fabricated, yielding a peak conversion efficiency of ∼7.2%, thereby advancing the performance of current Mg‐based TE modules. Overall, this study realizes the synergistic optimization of high‐performance TE materials and compatible TE interface materials, paving the way for the fabrication of efficient and scalable TE modules.