Abstract
Understanding the structural and physical origins of low thermal conductivity behavior is essential for improving and searching for high-efficiency thermoelectric materials. Natural minerals are cheap and usually have low thermal conductivities. The lattice thermal conductivities of two isostructural natural materials, chalcostibite and emplectite , are substantially low in experimental measurements. In particular, the lattice thermal conductivity of is much lower than that of . Using first-principles Debye-Callaway calculations, we found that the lattice thermal conductivities of and are 1.44 W/mK and 0.46 W/mK at 300 K, respectively, which are in good agreement with the experimental measurements. From the calculated vibrational properties, we demonstrate that the stereochemically active lone-pair electrons at the Sb sites are major contributors to the low thermal conductivity of . However, for , the dual effects of the lone-pair electrons at the Bi sites and the rattling of the Cu ions are the primary reasons for the ultralow thermal conductivity. Because of the ultralow thermal conductivity in , our predicted highest value in the material could reach 0.91 for -type doping at 700 K and 0.77 for -type doping at 780 K, which implies that can be utilized as a potential low-cost thermoelectric material for both and type. The present work emphasizes the importance of lone-pair electrons and rattling modes in impelling the phonon anharmonicity, providing a useful guide to seek and design new thermoelectric materials with ultralow thermal conductivity and high efficiency.
1 More- Received 28 September 2017
DOI:https://doi.org/10.1103/PhysRevB.96.235205
©2017 American Physical Society