Cubic AgMnSbTe₃ Semiconductor with a High Thermoelectric Performance

Abstract

The reaction of MnTe with AgSbTe₂ in an equimolar ratio (ATMS) provides a new semiconductor, AgMnSbTe₃. AgMnSbTe₃ crystallizes in an average rock-salt NaCl structure with Ag, Mn, and Sb cations statistically occupying the Na sites. AgMnSbTe₃ is a p-type semiconductor with a narrow optical band gap of ∼0.36 eV. A pair distribution function analysis indicates that local distortions are associated with the location of the Ag atoms in the lattice. Density functional theory calculations suggest a specific electronic band structure with multi-peak valence band maxima prone to energy convergence. In addition, Ag₂Te nanograins precipitate at grain boundaries of AgMnSbTe₃. The energy offset of the valence band edge between AgMnSbTe₃ and Ag₂Te is ∼0.05 eV, which implies that Ag₂Te precipitates exhibit a negligible effect on the hole transmission. As a result, ATMS exhibits a high power factor of ∼12.2 μW cm^-1 K^-2 at 823 K, ultralow lattice thermal conductivity of ∼0.34 W m^-1 K^-1 (823 K), high peak <i>ZT</i> of ∼1.46 at 823 K, and high average <i>ZT</i> of ∼0.87 in the temperature range of 400-823 K.