First-Principles Study of the Thermoelectric Properties of the Zintl Compound KSnSb

The unique structure of Zintl phases makes it an ideal system to realize the concept of phonon-glass and electron-crystal in the thermoelectric community. In this work, by combining first-principles calculations and Boltzmann transport theory for both electrons and phonons, the thermoelectric properties of the Zintl compound KSnSb are investigated, where the carrier relaxation time is accurately treated within the framework of electron–phonon coupling. It is demonstrated that the figure of merit value of KSnSb can reach ∼2.2 at 800 K. Such an extraordinary thermoelectric performance originates from the large Seebeck coefficient because of the multivalley band structures and particularly the low lattice thermal conductivity caused by mixed-bond characteristics.