Manipulating Anti‐Site Defects in <i>α</i>‐MgAgSb for Thermoelectric Cooling Enhancement

ABSTRACT α ‐MgAgSb is one of the few high‐performance thermoelectric materials near room temperature, thanks to its inherently suppressed lattice thermal conductivity. However, conventional approaches to optimizing electrical properties often inadvertently degrade carrier mobility, adversely impacting thermoelectric performance at lower temperatures. In this study, we discovered in an experiment that Mg‐Ag anti‐site defects exist in the lattice and create staggered nanoscale anti‐site zones in the matrix. This unique structure significantly scatters phonons while having a negligible influence on carrier transport due to the preservation of carrier transport channels. By fine‐tuning the formation energy of Mg‐Ag anti‐sites through Zn doping, both carrier transport and phonon scattering were successfully bolstered. Consequently, a high figure of merit ( zT ) of ~0.45 at 200 K and an average zT of ~0.75 within the low‐temperature range of 200–400 K can be achieved. Furthermore, a single‐pair device constructed using the obtained α ‐MgAgSb and commercial Bi 2 Te 3 legs exhibited a temperature difference of ~56 K at 325 K, showcasing promise for thermoelectric cooling applications. This demonstration underscores the efficiency of anti‐site manipulation as a means to enhance the thermoelectric cooling performance of α ‐MgAgSb.