Mg3+δSbxBi2-x Family: A Promising Substitute for the State-of-the-Art n-Type Thermoelectric Materials near Room Temperature

The Bi2Te3-xSex family has constituted n-type state-of-the-art thermoelectric materials near room temperature (RT) for more than half a century, which dominates the active cooling and novel heat harvesting application near RT. However, the drawbacks of a brittle nature and Te-content restricts the possibility for exploring potential applications. Here, it is shown that the Mg3+delta SbxBi2-x family ((ZT)(avg) = 1.05) could be a promising substitute for the Bi2Te3-xSex family ((ZT)(avg) = 0.9-1.0) in the temperature range of 50-250 degrees C based on the comparable thermoelectric performance through a synergistic effect from the tunable bandgap using the alloy effect and the suppressible Mg-vacancy formation using an interstitial Mn dopant. The former is to shift the optimal thermoelectric performance to near RT, and the latter is helpful to partially decouple the electrical transport and thermal transport in order to get an optimal RT power factor. The positive temperature dependence of the bandgap suggests this family is also a superior medium-temperature thermoelectric material for the significantly suppressed bipolar effect. Furthermore, a two times higher mechanical toughness, compared with the Bi2Te3-xSex family, allows for a promising substitute for state-of-the-art n-type thermoelectric materials near RT.