Enhanced Band Convergence and Ultra‐Low Thermal Conductivity Lead to High Thermoelectric Performance in SnTe

Abstract

SnTe, as tructural analogue of champion thermoelectric (TE) material PbTe, has recently attracted wide attention for TE energy conversion. Herein, we demonstrate ac o-doping strategy to improve the TE performance of SnTe via simultaneous modulation of electronic structure and phonon transport. The electrical transport is optimizedb y 3mol %A gd oping in self-compensated SnTe( i.e., Sn 1.03 Te). Further,Mgdoping in SnAg 0.03 Te resulted in highly converged valence bands,w hich enhanced the Seebeck coefficient markedly.T he energy gap between two uppermost valence bands (DE v )decreases to 0.10 eV in Sn 0.92 Ag 0.03 Mg 0.08 Te compared to 0.35 eV in pristine SnTe. The optimizedp-type carrier concentration and highly converged valence bands gave ahigh power factor of ca. 27 mWcm À1 K À2 at 865 Ki nS n 0.92 Ag 0.03 Mg 0.08 Te. The lattice thermal conductivity of Sn 0.92 Ag 0.03 Mg 0.08 Te reached to an ultra-low value of % 0.23 Wm À1 K À1 at 865 Kd ue to the formation of MgTen anoprecipitates in SnTem atrix. These combined effects resulted in ah igh TE figure of merit, zT % 1.55 at 865 Ki nSn 0.92 Ag 0.03 Mg 0.08 Te.

Enhanced Thermoelectric Performance of SnTe-Based Materials via Interface Engineering

“…49 Accordingly, its inset displays the selected-area electron diffraction (SAED) pattern indexed as the [011] zone axis of rock-salt-structured SnTe. The detailed microstructure and nanostructure analyses clarify the existence of multi-scale crystal imperfections, mainly including a high density of 54 and ΔE v = 0.28 eV (green line) 43 and in comparison with reported data on undoped SnTe, 56 Sn 1−x Sb x Te, 50 and Sn 1−x Sb 2x/3 Te. 42 nanoprecipitates at the grain boundary, porous structures, dense grain boundaries, and stacking faults in the grains, which is expected to impact the phonon transmission of the material, 11,12 which will be discussed later.…”

Band Engineering SnTe via Trivalent Substitutions for Enhanced Thermoelectric Performance

“…56 The Sn 0.92 Ag 0.03 Mg 0.08 Te compound is demonstrated to have a high zT ∼ 1.55 at 865 K via simultaneous modulation of electronic structure and inhibition of the phonon propagation. 57 By alloying SnTe with MnTe and GeTe, Sn 0.83 Ge 0.05 Mn 0.2 Te(Cu 2 Te) 0.05 achieves extraordinary thermoelectric performance (zT ∼ 1.8). 58 A high zT of 1.85 is obtained in SnTe via synergistic resonance levels, band convergence (Ca and In codoping), and endotaxial nanostructuring (Cu 2 Te).…”

“…Much of this improvement is attributed to the band convergence between L and Σ. , For example, the Ge–Mn codoped SnTe [(Sn 0.8 Ge 0.2 ) 0.85 Mn 0.15 Te] reached a high zT because the energy difference between L and Σ extrema decreases to 0.15 eV . The Sn 0.92 Ag 0.03 Mg 0.08 Te compound is demonstrated to have a high zT ∼ 1.55 at 865 K via simultaneous modulation of electronic structure and inhibition of the phonon propagation . By alloying SnTe with MnTe and GeTe, Sn 0.83 Ge 0.05 Mn 0.2 Te­(Cu 2 Te) 0.05 achieves extraordinary thermoelectric performance (zT ∼ 1.8) .…”

High Power Factor and Thermoelectric Figure of Merit in Sb2Si2Te6 through Synergetic Effect of Ca Doping

“…Since the Seebeck coefficient has an inverse proportional relationship with carrier concentration in theoretical. As known, it is meaningless to compare Seebeck coefficients alone, we then compared the measured Seebeck coefficients with the classical Pisarenko plot using the single parabolic band model, , Figure c. Obviously, the Seebeck coefficients for Ca doped Sb 2 Si 2 Te 6 are higher than the theoretical ones, indicating the substitution of Ca for Sb is conducive to enhancing the density of state effective mass m d * thus the Seebeck coefficients of Sb 2 Si 2 Te 6 .…”

“…Since the Seebeck coefficient has an inverse proportional relationship with carrier concentration in theoretical. As known, it is meaningless to compare Seebeck coefficients alone, we then compared the measured Seebeck coefficients with the classical Pisarenko plot using the single parabolic band model, 4,44 Thanks to the positive effects of Ca doping on both the electrical conductivity and Seebeck coefficient of Sb 2 Si 2 Te 6 , whose power factor S 2 σ was enhanced accordingly. As shown in Figure 5d, we achieved the highest S 2 σ of 13.5 μW m −1 K −2 at 573 K for Sb 1.97 Ca 0.03 Si 2 Te 6 (i.e., x = 0.03) along its crossplane direction, ∼30% increase in comparison with the value (10.6 μW m −1 K −2 (cross-plane) at 573 K) for Sb 2 Si 2 Te 6 .…”