High-performance MgAgSb/Mg3(Sb,Bi)2-based thermoelectrics with η = 12% at T ≤ 583K

Abstract

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.