α-MgAgSb, as a promising near-room-temperature thermoelectric (TE) material, has suffered from incompetent carrier mobility induced by the scattering of vacancies and grain boundaries. Synthesis of stoichiometric α-MgAgSb with large crystal grains has been challenging. Here, owing to an improved ball-milling process, the phase purity of α-MgAgSb powder precursor was effectively increased during mechanochemical synthesis. After subsequent spark plasma sintering (SPS) and post annealing at 583 K, near-stoichiometric α-MgAgSb exhibiting a mosaic structure was obtained, registering a significantly enhanced μ of 93.3 cm²V⁻¹s⁻¹ and zT_avg of 1.4 in 300–573 K. A 7-pair TE module based on α-MgAgSb/Mg₃BiSb was fabricated, which demonstrated a record-high efficiency of 12% at T_h ≤ 583 K and a cooling ΔT_max of 61 K at 300 K. This work lays the foundation for broad applications of Mg-based TEs.

α-MgAgSb作为一种有前途的近室温热电（TE）材料，由于空位和晶界的散射而导致载流子迁移率不足。具有大晶粒的化学计量 α-MgAgSb 的合成一直具有挑战性。这里，由于改进的球磨工艺，α-MgAgSb粉末前驱体的相纯度在机械化学合成过程中得到有效提高。随后进行放电等离子烧结 (SPS) 并在 583 K 进行后退火后，获得了呈现马赛克结构的近化学计量的 α-MgAgSb，在 300 小时内记录到显着增强的μ为 93.3 cm ² V ^-1 s ^-1和zT _avg为 1.4 –573 K。制造了基于 α-MgAgSb/Mg ₃ BiSb 的 7 对 TE 模块，该模块在 T _h ≤ 583 K 时表现出 12% 的创纪录高效率，在 300 K 时冷却 Δ T _max为 61 K这项工作为镁基TE的广泛应用奠定了基础。