Date Published:

Abstract:

We introduce Sb₂Si₂Te₆ as a high-performance thermoelectric material. Single-crystal X-ray diffraction analysis indicates that Sb₂Si₂Te₆ has a layered two-dimensional structure with Sb³⁺ cations and [Si₂Te₆]⁶⁻ units as building blocks adopting the Fe₂P₂Se₆ structure type. Sb₂Si₂Te₆ is a direct-band-gap semiconductor with valence-band maximum and conduction-band minimum at the Z point in the Brillouin zone, where the band is doubly degenerate. Polycrystalline bulk pellets of Sb₂Si₂Te₆ with randomly packed grains exhibit an intrinsically high thermoelectric figure of merit ZT of ∼1.08 at 823 K. We then create a cellular nanostructure with ultrathin Si₂Te₃ nanosheets covering the Sb₂Si₂Te₆ grains, which act as a hole-transmitting electron-blocking filter and at the same time cause extra phonon scattering. This dual function of the cellular nanostructure achieves an ultralow thermal conductivity value of ∼0.29 Wm⁻¹K⁻¹ and a high ZT value of ∼1.65 at 823 K for Sb₂Si₂Te₆, along with a high average ZT value of ∼0.98.

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