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Realizing a stable high thermoelectric zT ∼ 2 over a broad temperature range in Ge1−xyGaxSbyTe via band engineering and hybrid flash-SPS processing

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Abstract

We report a remarkably high and stable thermoelectric figure of merit zT close to 2 by manipulating the electronic bands in Ga–Sb codoped GeTe, which has been processed by hybrid flash-spark plasma sintering. According to the experimental results and first-principles calculations, the vast enhancement achieved in the thermopower due to codoping of Ga (2 mol%) and Sb (8 mol%) in GeTe is attributed to a concoction of reasons: (i) suppression of hole concentration; (ii) improved band convergence by decreasing the energy separation between the two valence band maxima to 0.026 eV; (iii) Ga predominantly contributing to the top of the valence band in Ga–Sb codoped GeTe, despite the Ga-induced resonance state not being located at a favorable position near the Fermi level; (iv) active participation of several bands increasing the hole carrier effective mass; (v) facilitating band degeneracy by reducing the R3mFm[3 with combining macron]m structural transition temperature from 700 K to 580 K. The synergy between these complementary and beneficial effects, in addition to the reduced thermal conductivity, enabled the flash sintered Ge0.90Ga0.02Sb0.08Te composition to not only exhibit a peak of zT of ∼1.95 at 723 K, but also to maintain/stabilize its high performance over a broad temperature range (600–775 K), thus making it a serious candidate for mid-temperature range energy harvesting devices.

Graphical abstract: Realizing a stable high thermoelectric zT ∼ 2 over a broad temperature range in Ge1−x−yGaxSbyTe via band engineering and hybrid flash-SPS processing

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Publication details

The article was received on 16 Jul 2018, accepted on 03 Oct 2018 and first published on 03 Oct 2018


Article type: Research Article
DOI: 10.1039/C8QI00703A
Citation: Inorg. Chem. Front., 2018, Advance Article
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    Realizing a stable high thermoelectric zT ∼ 2 over a broad temperature range in Ge1−xyGaxSbyTe via band engineering and hybrid flash-SPS processing

    B. Srinivasan, A. Gellé, F. Gucci, C. Boussard-Pledel, B. Fontaine, R. Gautier, J. Halet, M. J. Reece and B. Bureau, Inorg. Chem. Front., 2018, Advance Article , DOI: 10.1039/C8QI00703A

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