Zintl-phase Eu ₂ ZnSb ₂ : A promising thermoelectric material with ultralow thermal conductivity

Significance Searching for compounds with intrinsic low lattice thermal conductivity has been proven a successful strategy for achieving high thermoelectric performance. Here we report a promising 2-1-2–type Eu 2 ZnSb 2 ( P 6 3 / mmc ) Zintl-phase thermoelectric material. Its intrinsic crystal structure, together with its widely distributed plane defects, likely contribute to its effective phonon scattering, leading to ultralow thermal conductivity (∼0.41 W m −1 ⋅K −1 at 300 K and ∼0.37 W m −1 ⋅K −1 at 623 K), lower than that of most other Zintl compounds. By regulating the Zn deficiency, the maximum ZT value of Eu 2 Zn 0.98 Sb 2 reaches ∼1.0 at 823 K, which is quite respectable for p-type Zintl materials. This discovery provides a class of Zintl thermoelectric materials applicable in the medium-temperature range.