Chemical Bonding Tuned Lattice Anharmonicity Leads to a High Thermoelectric Performance in Cubic AgSnSbTe<sub>3</sub>
Debattam Sarkar, Kapildeb Dolui, Vaishali Taneja, Abdul Ahad, Moinak Dutta, S. O. Manjunatha, Diptikanta Swain, Kanishka Biswas
Abstract
Abstract Comprehension of chemical bonding and its intertwined relation with charge carriers and heat propagation through a crystal lattice is imperative to design compounds for thermoelectric energy conversion. Here, we report the synthesis of large single crystal of new p ‐type cubic AgSnSbTe 3 which shows an innately ultra‐low lattice thermal conductivity (κ lat ) of 0.47–0.27 Wm −1 K −1 and a high electrical conductivity (1238 – 800 S cm −1 ) in the temperature range 294–723 K. We investigated the origin of the low κ lat by analysing the nature of the chemical bonding and its crystal structure. The interaction between Sn(5 s )/Ag(4 d ) and Te(5 p ) orbitals was found to generate antibonding states just below the Fermi level in the electronic band structure, resulting in a softening of the lattice in AgSnSbTe 3 . Furthermore, the compound exhibits metavalent bonding which provides highly polarizable bonds with a strong lattice anharmonicity while maintaining the superior electrical conductivity. The electronic band structure exhibits nearly degenerate valence‐band maxima that help to achieve a high Seebeck coefficient throughout the measured temperature range and, as a result, the maximum thermoelectric figure of merit reaches to ≈1.2 at 661 K in pristine single crystal of AgSnSbTe 3 .