A low-temperature thermoelectric transport study of non-stoichiometric AgSbTe₂

In recent times, considerable attention has been given to examining the impact of micro/nanostructure on the thermoelectric characteristics of nonstoichiometric AgSbTe₂. The present investigation employed direct melting of elements that produced p-type AgSbTe₂ with spontaneous nanostructuring due to cation ordering. The product predominantly features an Ag-deficient Ag_0.927Sb_1.07Te_2.005 phase with monoclinic Ag₂Te nanoprecipitates and exhibits a degenerate semiconductor-like behavior with an energy band gap of 0.15 eV. A Seebeck coefficient of 251 μV K^-1 and a power factor of 741 μW m^-1 K^-2 at near ambient temperature are attained with this composition. The variable range hopping (VRH) and linear magnetoresistance (LMR) confirmed that the low-temperature transport followed a VRH between the localized states. The composition also exhibited glass like thermal conductivity of 0.2 W m^-1 K^-1 arising from phonon scattering at all-scale hierarchical structures that led to a high ZT of 1.1 at room temperature. The direct melted ingots show a high relative density of ∼97%, Vickers hardness H_v of ∼108.5 kgf mm^-2, and excellent thermal stability, making them an attractive choice for TEGs.