Optimization of Thermoelectric Property of n‐Type Mg3Sb2 Near Room Temperature via Mn&Se Co‐Doping

Abstract The Bi 2 Te 3 family has been considered a state‐of‐the‐art thermoelectric material for room‐temperature applications for over half a century. However, scarcity of the material Te has been a persistent issue. Recently, the discovery of n‐type Mg 3 (Bi, Sb) 2 ‐based materials provides new hope for replacing traditional Bi 2 Te 3 , but their thermoelectric properties near room temperature still need improvement for application to practical devices. Herein, a competitive figure of merit of ≈0.8 at 300 K and a high power factor greater than 30 µW cm −1 K −2 at 300 K in n‐type Mg 3.14 Mn 0.06 Bi 1.4 Sb 0.59 Se 0.01 is reported, benefiting from the rationally tuned carrier concentration of 2.29×10 19 cm −3 at room temperature. Substituting the Mg site with Mn in Mg 3.2 Bi 1.4 Sb 0.59 Se 0.01 changes the dominant carrier scattering mechanism from a mixed scattering of acoustic phonons and ionized impurities to acoustic phonon scattering. Mn doping in Mg 3.2 Bi 1.4 Sb 0.59 Se 0.01 also enhances the mobility to 180 cm 2 V −1 s −1 , reduces the thermal conductivity, and significantly increases the quality factor β of the material. The high room temperature thermoelectric performance of n‐type Mn&Se co‐doped Mg 3 (Bi, Sb) 2 ‐based materials makes them a highly competitive substitute for commercialized n‐type Bi 2 Te 3 .