Advancing Nontoxic, Antimony-based 1–2–2-type Thermoelectric Zintls

We present our investigations on designing nontoxic, antimony-based 1–2–2 p-type Zintl thermoelectric materials and on understanding their intrinsic physical properties. First, electronic band convergence can have a beneficial impact on thermoelectric performance, but finding the right band-converged compositions is still time-consuming. We present our original method for designing a series of compositions with simultaneous band convergence in the high-entropy Yb_xCa_1−xMg_yZn_2−ySb₂ material by zeroing the weighted sum of crystal-field splitting energies of the parent compounds. Second, 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), as well as those for a few other unusual transport behaviors we have identified in AMg₂Sb₂.