Entropy engineering promotes thermoelectric performance in p-type chalcogenides

Binbin Jiang,Juan Cui,Jiaqing He,Xixi Liu,Yong Yu,Lin Xie,Hongyi Chen

doi:10.1038/s41467-021-23569-z

Binbin Jiang, Juan Cui + Show 5 more

Open Access

https://doi.org/10.1038/s41467-021-23569-z

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Abstract

We demonstrate that the thermoelectric properties of p-type chalcogenides can be effectively improved by band convergence and hierarchical structure based on a high-entropy-stabilized matrix. The band convergence is due to the decreased light and heavy band energy offsets by alloying Cd for an enhanced Seebeck coefficient and electric transport property. Moreover, the hierarchical structure manipulated by entropy engineering introduces all-scale scattering sources for heat-carrying phonons resulting in a very low lattice thermal conductivity. Consequently, a peak zT of 2.0 at 900 K for p-type chalcogenides and a high experimental conversion efficiency of 12% at ΔT = 506 K for the fabricated segmented modules are achieved. This work provides an entropy strategy to form all-scale hierarchical structures employing high-entropy-stabilized matrix. This work will promote real applications of low-cost thermoelectric materials.

Highlights

We demonstrate that the thermoelectric properties of p-type chalcogenides can be effectively improved by band convergence and hierarchical structure based on a high-entropystabilized matrix
Upon introducing Na, the split peaks converged into one peak illustrating the resulting single phase. This phenomenon was observed in Snalloyed (Pb,Sn)(Se,S,Te) system and can be well explained by the entropy-driven structural stabilization[18,22]
The band convergence due to the decreased energy offset between light and heavy valence bands benefitted from an enhanced power factor

Summary

Introduction

We demonstrate that the thermoelectric properties of p-type chalcogenides can be effectively improved by band convergence and hierarchical structure based on a high-entropystabilized matrix. The hierarchical structure manipulated by entropy engineering introduces all-scale scattering sources for heat-carrying phonons resulting in a very low lattice thermal conductivity. We synthesized high-entropy Pb0.975Na0.025Se0.5S0.25Te0.25 compositions whose structure was stabilized by increasing the entropy This increased the peak zT to a high value of 2.0 at 900 K with band convergence and hierarchical structures (Fig. 1a). The hierarchical structures manipulated by introducing complicated elemental composition demonstrated different scales of lattice defects (Fig. 1c) These scatter all-frequency phonons and contributed to a very low lattice thermal conductivity (κL) of 0.33 Wm−1K−1 for Pb0.935Na0.025Cd0.04Se0.5S0.25Te0.25 sample.

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