Exploring the atomic and electronic structures of low thermal conductivity materials using a combined XAS and DFT approach

Abstract

This study revealed the atomic and electronic structures of Sn(SbTe₂)₂ and ZrW₂O₈ using X-ray absorption spectroscopy (XAS) coupled with density functional theory (DFT) calculations. The XAS analysis of Sn(SbTe₂)₂ revealed that Sn predominantly existed in the +4 oxidation state, with spectral features closely resembling those of SnO₂. Sb was identified in the +3 oxidation state, consistent with the reference Sb₂O₃, while Te exhibited features characteristic of the −2 oxidation state, similar to those found in metal tellurides. These oxidation states suggest strong electron localization and structural stabilization effects within the ternary compound. The study of ZrW₂O₈ showed that Zr was predominantly 6-fold coordinated, which influenced its thermal properties. The DFT calculations indicated that both α- and β-ZrW₂O₈ were wide-band-gap semiconductors, with band gaps of 3.35 eV and 3.51 eV, respectively. While the α-ZrW₂O₈ band gap was consistent with theoretical predictions, it remained lower than experimental values. The phase transition from the α to β phase of ZrW₂O₈ led to increasing somewhat the energy band gap and enhancing p-type charge transport resulting in promising thermoelectric applications. These findings provided important atomic and electronic structural insights, revealing the mechanisms behind the low thermal conductivity in these materials. These results contributed to the design of advanced materials with optimized thermal properties, advancing energy efficiency and thermal management technologies.