Impurity Band Engineering and Hierarchical Defect Scattering Enable High zT in Co-Doped AgSbTe2

Impurity Band Engineering and Hierarchical Defect Scattering Enable High zT in Co-Doped AgSbTe2

AgSbTe2 is a promising p-type thermoelectric material for mid-temperature applications. However, its performance is limited by its low electrical conductivity and the presence of an n-type Ag2Te secondary phase. In this study, a series of AgSb1−xCoxTe samples were synthesized by conventional melting followed by spark plasma sintering. Co doping suppresses the formation of the detrimental Ag2Te phase and introduces an impurity band above the valence band maximum, as revealed by the calculated electronic structures. Moreover, Co incorporation generates multi-scale lattice defects that act as efficient phonon scattering centers, resulting in remarkably low thermal conductivity. Consequently, a peak thermoelectric figure of merit of 1.6 was achieved at 648 K. These results demonstrate a practical doping strategy that preserves favorable charge transport in AgSbTe2 while strongly reducing its thermal conductivity, offering a clear pathway toward improving mid-temperature thermoelectric modules.

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