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Electronic structure of Ba-Ga-Ge-Si Type I Clathrates: A Ge and Ga K-Edge Study



Winnie Wong-Ng, Azzam Mansour, Joshua B. Martin, George S. Nolas


XANES spectroscopy was successfully used to study changes in the density of unoccupied states for silicon substituted Ba8Ga16Ge30-xSix type I clathrates. Partial density of unoccupied states with p character is modified for both Ga and Ge upon Si substitution with the greatest changes occurring for the sample with the highest power factor (S2σ, where S is the Seebeck coefficient, σ the electrical conductivity). Our experimental results provide a strong correlation with computational results based on density functional theory, indicating that a series of pertinent electronic states are modified by Si p states. This suggests that an increase in the electron density near the Fermi level for an optimal Si substitution leads to an increase in the Seebeck coefficient and consequently in the power factor, according to the Mott relation. Understanding the underlying physics of this structure-property relationship could indicate additional routes for tuning the electronic properties of these materials for thermoelectric applications.
Journal of Physics: Condensed Matter


XANES, Type I clathrate, thermoelectric material, Ba8Ga16Ge30-xSix, Seebeck coefficient, Ge and Ga K-edge


Wong-Ng, W. , Mansour, A. , Martin, J. and Nolas, G. (2012), Electronic structure of Ba-Ga-Ge-Si Type I Clathrates: A Ge and Ga K-Edge Study, Journal of Physics: Condensed Matter (Accessed May 29, 2024)


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Created November 9, 2012, Updated November 1, 2022