Physical origins of the varying performance and unusual transport behaviors among thermoelectric AMg2Sb2 materials (A = Ca, Sr, Sm, Yb, and Mg)

Contrary to the similar thermoelectric performance among both AZn2Sb2 and AMg2Bi2 compounds, their isostructural counterparts, AMg2Sb2, can exhibit thermoelectric figure of merit values that vary by orders of magnitude with different A elements. Here, we reveal physical origins accounting for the significantly differing performance among AMg2Sb2-based compounds (A = Ca, Sr, Sm, Yb, and Mg) through comprehensive analyses, where it is shown that the disparities in performance at the macroscale essentially originate from the widely varying activation energies that equal amounts of dopant can induce. Meanwhile, a few unusual transport behaviors regarding electrical conductivity, carrier concentration, or lattice thermal conductivity among these compounds have been identified, and we also present their rationales in depth. This mechanism-focused study can not only promote further understanding of the complex transport behaviors in condensed matter but be instrumental in rationally tuning the physical properties of materials as well.