Theoretical Study on Thermoelectric Performance of N‐Type Mg3(Sb,Bi)2 Single Crystal for Cooling or Power Generation

Abstract Mg 3 Sb 2 ‐based Zintl compounds have been paid much attention in recent years because of their high peak figure of merit ( zT ), however, there is room for the improvement of the average zT . In this work, the thermoelectric performance of Mg 3 (Sb,Bi) 2 single crystal by using density functional theory is investigated. The optimal carrier concentration ( n ) of Mg 3 SbBi is 2 × 10 19 to 3 × 10 20 cm –3 at 100−700 K. At the n of 3 × 10 19 cm –3 , it can exhibit a high average zT of ≈1.27 at cold‐side temperature ( T c ) of 300 K and hot‐side temperature ( T h ) of 700 K, and the electrical transport performance can be further improved by increasing the n . When the optimal n is reached, the maximum average zT of Mg 3 SbBi at T c of 100 K and T h of 300 K can be up to 0.54, which is comparable to that of state‐of‐the‐art Bi 2 (Te,Se) 3 . Because the decreasing trend of the optimal n with temperature, the maximum low‐temperature thermoelectric performance is easier to be achieved by less extrinsic doping. This work reveals the great potential of Mg 3 (Sb,Bi) 2 single crystal for thermoelectric cooling or power generation, which is expected to provide useful guidance for thermoelectric devices.