Tailoring the Thermoelectric Performance of the Layered Topological Insulator SnSb₂Te₄ through Bi Positional Doping at the Sn and Sb Cation Sites

Abstract

Ongoing research and development focus on emerging thermoelectric materials with enhanced performance, continually making the possibility of waste heat recovery a reality. In this work, we engineer the thermoelectric properties of the layered SnSb2Te4 topological insulators. To date, there is little research reporting on these materials as potential state-of-the-art thermoelectric materials. Thus, there is a need to formulate effective strategies to realize this potential. Since these materials are known to have intrinsically low lattice thermal conductivity, we shift our attention to improving the electrical transport properties. For the first time, positional Bi doping at both the Sn and Sb cation sites is adopted. The aliovalent and isovalent nature of Bi at these sites, respectively, is shown to cause significant improvements in the performance of these layered materials. The electronic band structure of the pure and doped samples, where we considered various occupancies, is studied whereby we reveal the occurrence of band convergence and resonant levels resulting in a high power factor of ∼10.8 μW cm–1 K–2 at 623 K. Overall, a high ZT of ∼0.46 at a relatively lower temperature of 673 K is recorded. The potential of these materials for thermoelectric applications is shown, especially in the case of Bi doping at the Sn cation site. Continued efforts to enhance the thermoelectric performance of these topological insulators are needed for them to gain a substantial competitive edge in comparison to other state-of-the-art thermoelectric materials.

Topological Insulators for Thermoelectrics: A Perspective from Beneath the Surface

“…Aside from the ones in this review, we believe that there are other known TI families where unconventional TE phenomena can be observed, such as (SnSe) 1−x (ABX 2 ) x alloys [102][103][104][105][106][107][108] and the homologous series of ternary (TrCh) n (Pn 2 Ch 3 ) m compounds, where Tr = tetrel (Ge, Sn, Pb), Pn = pnictogen (Sb, Bi), and Ch = chalcogen (Se, Te). [109][110][111][112][113] A more holistic understanding of band inversion-driven effects, complete with generalized models and case studies of specific materials, will enrich design strategies to improve zT in TI-based TEs. Since commercial Peltier cooling devices are typically composed of TI alloys (Bi 2 Te 3−x Se x for the n-type leg and Bi 2−x Sb x Te 3 for the p-type leg), better understanding of bulk TE properties unique to TIs also holds technological and economical significance.…”

Enhanced Topological Surface State Mediated Transport Elevates Thermoelectric Performance in SnSb2Te4 Quantum Material

“…SnSb 2 Te 4 [i.e., (SnTe) 1 (Sb 2 Te 3 ) 1 ] in the homologous Sn m Sb 2 n Te 3 n + m family is a layered material with a tetradymite type structure ( R- 3 m space group) and can be described as intergrowth of SnTe-type (rocksalt) and Sb 2 Te 3 -type (hexagonal) phases (Figure a). , SnSb 2 Te 4 is a strong TI , having a single Dirac cone with its Fermi level deep into the bulk states as probed through angle-resolved two-photon photoemission experiment previously . While its narrow band gap and presence of multiple valence band maxima near E F is appropriate for high power factor (σS 2 ), van der Waals layered structure (Figure a) on the other hand leads to an intrinsically ultralow κ L , making it a suitable candidate for TE application. − However, its high carrier concentration eventually leads to a high κ e and low S , which drag down the TE performance of pristine SnSb 2 Te 4 . Moreover, the carrier mobility is found to be significantly low, making it imperative to devise a strategy that optimizes charge carriers while simultaneously maintaining high mobility.…”