Solute manipulation enabled band and defect engineering for thermoelectric enhancements of SnTe

Abstract

With years of development, SnTe as a homologue of PbTe has shown great potential for thermoelectric applications in p‐type conduction, and the most successful strategy is typified by alloying for maximizing the valence band degeneracy. Among the known alloy agents, MnTe has been found to be one of the most effective enabling a band convergence for an enhancement in electronic performance of SnTe, yet its solubility of only ~15 at% unfortunately prevents a full optimization in the valence band structure. This work reveals that additional PbTe alloying not only promotes the MnTe solubility to locate the optimal valence band structure but also increases the overall substitutional defects in the material for a substantial reduction in lattice thermal conductivity. In addition, PbTe alloying simultaneously optimizes the carrier concentration due to the cation size effect. These features all enabled by such a solute manipulation synergistically lead to a very high thermoelectric figure of merit, zT of ~1.5 in SnTe with a 20 at% MnTe and a 30 at% PbTe alloying (Sn0.5Mn0.2Pb0.3Te), demonstrating the effectiveness of solute manipulation for advancing SnTe and similar thermoelectrics.

Slowing down the heat in thermoelectrics

“…Simultaneously, these extrinsic defects play a key role in strengthening phonon scattering and reducing κ lat 37,67,68 . Zero‐dimensional (0D) point defects, such as atomic substitutions, vacancies, and interstitial and filling atoms in specific structures, can strongly scatter high‐frequency phonons by inducing atomic‐scale lattice distortions and high‐density strains around them, 22,32,69–72 thereby decreasing κ lat . One‐dimensional (1D) linear defects, mainly existing as edge dislocations in thermoelectric materials, scatter mid‐frequency phonons 22,73,74 .…”

Remarkable Improvement of Thermoelectric Figure-of-Merit in SnTe through In Situ-Created Te Nanoinclusions

“…Such an unfavorable trend of thermoelectric parameters results in very low figure-of-merit ( ZT ) ≪ 1 for pristine SnTe. Various strategies have been employed to improve the Seebeck coefficient of SnTe including electronic band engineering, optimization of the carrier concentration, and introduction of the resonance states in the valence band. , Additionally, by employing cumulative approaches such as improving the power factor through band convergence, , energy filtering, and lowering of lattice thermal conductivity by introducing endotaxial precipitation resulted in huge improvement in ZT of SnTe. − The study by Brebrick and Strauss shows that the Seebeck coefficient of SnTe shows a very anomalous dependence on the carrier concentration because of the existence of two valence bands. With an increasing carrier concentration, the Fermi level crosses three regions: the I-light hole valence band (L band), II-light hole (L) and partial heavy hole (∑) bands, and III-L band and ∑ bands.…”

Enhanced thermoelectric performance of ternary compound Cu3PSe4 by defect engineering

“…Fortunately, the lattice thermal conductivity is the relatively independent parameter among above transport parameters. Therefore, it is feasible to discover some novel TE compounds with intrinsically low thermal conductivity where we can start to tune the electrical transport properties through regulating carrier concentration, scattering mechanisms or band degeneracy, such as the accomplishment in SnSe, Mg 3 Sb 2 and BiCuSeO [9][10][11][12][13][14]. Recent studies have shown that the complex derivative compounds with a series of primitive cells based on Groups II-VI such as ternary I-III-VI 2 , II-IV-V 2 , II-III 2 -VI 4 , I 2 -IV-VI 3 , I 3 -V-VI 4 and quaternary I 2 -II-IV-VI 4 compounds can be synthesized [15][16][17][18][19].…”