Intrinsically Low Thermal Conductivity in BiSbSe₃: A Promising Thermoelectric Material with Multiple Conduction Bands

Abstract

Bi 2 Se 3 , as a Te-free alternative of room-temperature state-of-the-art thermoelectric (TE) Bi 2 Te 3 , has attracted little attention due to its poor electrical transport properties and high thermal conductivity. Interestingly, BiSbSe 3 , a product of alloying 50% Sb on Bi sites, shows outstanding electron and phonon transports. BiSbSe 3 possesses orthorhombic structure and exhibits multiple conduction bands, which can be activated when the carrier density is increased as high as ≈3.7 × 10 20 cm −3 through heavily Br doping, resulting in simultaneously enhancing the electrical conductivities and Seebeck coefficients. Meanwhile, an extremely low thermal conductivity (≈0.6-0.4 W m −1 K −1 at 300-800 K) is found in BiSbSe 3 . Both first-principles calculations and elastic properties measurements show the strong anharmonicity and support the ultra-low thermal conductivity of BiSbSe 3 . Finally, a maximum dimensionless figure of merit ZT ∼ 1.4 at 800 K is achieved in BiSb(Se 0.94 Br 0.06 ) 3 , which is comparable to the most n-type Te-free TE materials. The present results indicate that BiSbSe 3 is a new and a robust candidate for TE power generation in medium-temperature range.

Chalcogenide Thermoelectrics Empowered by an Unconventional Bonding Mechanism

“…While GeTe reveals a maximum zT of 1.0 at 673 K, GeSe shows a zT of 0.05 at 710 K . A similar observation can be made upon comparing Bi 2 Se 3 with Bi 2 S 3 , which differ by more than a factor of 10 in zT . Such pronounced differences for isoelectronic materials are striking and call for an explanation.…”

Intrinsically Low Thermal Conductivity and High Carrier Mobility in Dual Topological Quantum Material, n‐Type BiTe

“…The presence of wiggly bands, characterized by the multiple band extrema and valley degeneracies in the electronic bands near the Fermi level significantly enhances the Seebeck coefficients of materials . The spin‐orbit coupled electronic structure (Figure c) of BiTe exhibits multiple pockets in its conduction band, as discussed in the previous section.…”

“…Ty pically, S of BiTealong SPS ll increases from À42.3 mVK À1 at 297 KtoÀ74.9 mVK À1 at 600 K, then, S value decreases to À72.2 mVK À1 at 650 K. Thep resence of wiggly bands,c haracterized by the multiple band extrema and valley degeneracies in the electronic bands near the Fermi level significantly enhances the Seebeck coefficients of materials. [24,47,48] Thes pin-orbit coupled electronic structure (Figure 2c)o fB iTee xhibits multiple pockets in its conduction band, as discussed in the previous section. Several band-edges appear just within 10 meV above the CBM (at the Lp oint), which is smaller than the thermal broadening (ca.…”

Surface Reconstruction, Oxidation Mechanism, and Stability of Cd3As2

“…Recently, Dirac fermions have been predicted also in monolayer B 2 S and Na 2 C . However, the great complication of implementing a monolayer thickness has motivated the interest of the scientific community toward systems displaying Dirac fermions in the bulk, such as 3D topological insulators (bismuth chalcogenides), in which surface states form Dirac cones . Nevertheless, surface states can be modified upon interaction with environmental species, up to be quenched in surfaces displaying chalcogenide vacancies, which inevitably drive rapid surface oxidation and degradation in ambient atmosphere.…”