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Description
Bismuth telluride (Bi$_2$Te$_3$), antimony telluride (Sb$_2$Te$_3$), and their solid solutions (Bi$_{2-x}$Sb$_x$Te$_3$) are among the most widely used thermoelectric (TE) materials owing to their excellent thermoelectric performance near room temperature.
Bi$_2$Te$_3$ and Sb$_2$Te$_3$ are isostructural compounds with complex two-dimensional layered structures consisting of Te2-Bi(Sb)-Te1-Bi(Sb)-Te2 quintuple layers, which are weakly bonded by van der Waals interactions. This layered architecture plays a crucial role in enabling their high thermoelectric efficiency. The pronounced structural anisotropy facilitates efficient in-plane charge carrier transport while effectively suppressing cross-plane lattice thermal conductivity. Owing to their structural compatibility, Bi and Sb readily substitute for one another on the cation sublattice, giving rise to continuous solid solutions (Bi$_{2-x}$Sb$_x$Te$_3$) with tunable electronic and thermal transport properties.
In this study, we employed synchrotron radiation X-ray absorption spectroscopy in combination with advanced reverse Monte Carlo simulations with evolutionary algorithm approach (RMC/EA) [1] to probe the composition- and temperature-dependent (10 – 300 K) evolution of the local atomic structure in Bi$_{2-x}$Sb$_x$Te$_3$ (x=0-2). Local lattice distortions originating from the ionic radius mismatch between Bi$^{3+}$ (1.03 Å) and Sb$^{3+}$ (0.76 Å) cations were clearly resolved. By extending the structural analysis to distant coordination shells, encompassing both intralayer and interlayer interactions, we were able to capture subtle disorder effects and correlate them with TE properties [2]. The extracted mean-square relative displacement (MSRD) factors and effective interatomic force constants highlight the strong anisotropy of thermal conductivity inherent to these layered architectures.
References
[1] Timoshenko J., Kuzmin A., Purans J. (2014), EXAFS study of hydrogen intercalation into ReO$_3$ using the evolutionary algorithm, J. Phys.: Condens. Matter 26, 055401.
[2] Hamawandi, B., Parsa, P., Pudza, I., Pudzs, K., Kuzmin, A., Ballikaya, S., Welter, E., Szukiewicz, R., Kuchowicz, M., \& Toprak, M. S. (2025). Scalable solution chemical synthesis and comprehensive analysis of Bi$_2$Te$_3$ and Sb$_2$Te$_3$. Energy Materials, 5, 500065.
