Local structure displacements and electronic structure of Sb-substituted rock-salt type AgBi1−xSbxSe0.8S0.6Te0.6 system

The cubic phase of the high-entropy alloy AgBi1−xSbxSe0.8S0.6Te0.6 compound, characterized by the substitution of Sb for Bi in the structure to enhance phonon scattering, has been analyzed for local atomic displacements and electronic structure using a combination of X-ray absorption and X-ray photoelectron spectroscopy techniques. Notably, Ag K-edge and Bi L3-edge X-ray absorption measurements demonstrate a contraction of bond distances upon substitution due to the smaller size of Sb. Conversely, X-ray photoelectron spectroscopy reveals that, while Ag remains predominantly in the Ag1+ state across all samples, Bi and Sb exhibit a single valence state only for minimal Sb substitution. At higher Sb substitution levels, both Bi and Sb manifest mixed valence states, indicating complex electronic behavior that potentially influences the thermoelectric properties of the system. These findings suggest that optimizing the local structure through Sb substitution can be beneficial in enhancing the material’s thermoelectric performance.