Issue 24, 2023

High thermoelectric performance in entropy-driven Ge1−2xyPbxSnxSbyTe

Abstract

Germanium telluride (GeTe) is one of the most fascinating inorganic compounds in thermoelectrics due to its intriguing chemical bonding, crystal and electronic structure. However, thermoelectric performance of pristine GeTe is greatly affected by its high lattice thermal conductivity and intrinsically high p-type carrier concentration. Recently, innovative strategies have been applied to improve thermoelectric performance either by enhancing electronic transport or decreasing the lattice thermal conductivity by phonon scattering. Herein, in order to increase the configurational entropy of the system, we have doped Sn and Pb (2.5 mol% each) in GeTe, which reduces the lattice thermal conductivity (κL) from 2.8 W m−1 K−1 of pristine GeTe to ∼1.9 W m−1 K−1 of Ge0.95Pb0.025Sn0.025Te sample at room temperature. Furthermore, we have doped donor dopant Sb on the Ge site in Ge0.95Pb0.025Sn0.025Te which optimizes the p-type carrier concentration of the system and enhances the Seebeck coefficient due to valence band convergence. Finally, high energy ball-milling along with spark plasma sintering (BM + SPS) has been performed, which helps in further enhancement of the Seebeck coefficient due to extreme valence band convergence and reduction in lattice thermal conductivity to ∼0.63 W m−1 K−1. As a result, a high thermoelectric figure of merit, zT of ∼2.3 (with Dulong–Petit Cp, zT is 2.5) at 723 K and a high average zTavg of 1.3 in the 300–723 K temperature range have been achieved in BM + SPS processed Ge0.84Pb0.025Sn0.025Sb0.11Te sample. Motivated by the ultra-high zT, we have constructed a double-leg TE device of Ge0.84Pb0.025Sn0.025Sb0.11Te (BM + SPS) sample as a p-type leg, where In and I doped PbTe is used as the n-type leg, which shows a high output power density (PDmax) of ∼590 mW cm−2 at ΔT = 448 K.

Graphical abstract: High thermoelectric performance in entropy-driven Ge1−2x−yPbxSnxSbyTe

Supplementary files

Article information

Article type
Paper
Submitted
21 Nov 2022
Accepted
23 Jan 2023
First published
24 Jan 2023

J. Mater. Chem. A, 2023,11, 12793-12801

High thermoelectric performance in entropy-driven Ge1−2xyPbxSnxSbyTe

A. Das, P. Acharyya, S. Das and K. Biswas, J. Mater. Chem. A, 2023, 11, 12793 DOI: 10.1039/D2TA09075A

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