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Title: Rhombohedral to Cubic Conversion of GeTe via MnTe Alloying Leads to Ultralow Thermal Conductivity, Electronic Band Convergence, and High Thermoelectric Performance

Journal Article · · Journal of the American Chemical Society
DOI:https://doi.org/10.1021/jacs.7b13611· OSTI ID:1775445

In this study, a series of Ge1–xMnxTe (x = 0–0.21) compounds were prepared by a melting–quenching–annealing process combined with spark plasma sintering (SPS). The effect of alloying MnTe into GeTe on the structure and thermoelectric properties of Ge1–xMnxTe is profound. With increasing content of MnTe, the structure of the Ge1–xMnxTe compounds gradually changes from rhombohedral to cubic, and the known R3m to Fm-3m phase transition temperature of GeTe moves from 700 K closer to room temperature. First-principles density functional theory calculations show that alloying MnTe into GeTe decreases the energy difference between the light and heavy valence bands in both the R3m and Fm-3m structures, enhancing a multiband character of the valence band edge that increases the hole carrier effective mass. The effect of this band convergence is a significant enhancement in the carrier effective mass from 1.44 m0 (GeTe) to 6.15 m0 (Ge0.85Mn0.15Te). In addition, alloying with MnTe decreases the phonon relaxation time by enhancing alloy scattering, reduces the phonon velocity, and increases Ge vacancies all of which result in an ultralow lattice thermal conductivity of 0.13 W m–1 K–1 at 823 K. Subsequent doping of the Ge0.9Mn0.1Te compositions with Sb lowers the typical very high hole carrier concentration and brings it closer to its optimal value enhancing the power factor, which combined with the ultralow thermal conductivity yields a maximum ZT value of 1.61 at 823 K (for Ge0.86Mn0.10Sb0.04Te). In conclusion, the average ZT value of the compound over the temperature range 400–800 K is 1.09, making it the best GeTe-based thermoelectric material.

Research Organization:
Northwestern Univ., Evanston, IL (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES); Natural Science Foundation of China
Grant/Contract Number:
SC0014520; 51402222; 51521001; 51632006
OSTI ID:
1775445
Journal Information:
Journal of the American Chemical Society, Vol. 140, Issue 7; ISSN 0002-7863
Publisher:
American Chemical Society (ACS)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 256 works
Citation information provided by
Web of Science

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Cited By (18)

Anisotropic thermal transport in van der Waals layered alloys WSe 2(1- x ) Te 2 x journal June 2018
Impurity states in Mo 1−x M x Se 2 compounds doped with group VB elements and their electronic and thermal transport properties journal January 2020
Is LiI a Potential Dopant Candidate to Enhance the Thermoelectric Performance in Sb-Free GeTe Systems? A Prelusive Study journal February 2020
High Thermoelectric Performance in the Wide Band‐Gap AgGa 1‐ x Te 2 Compounds: Directional Negative Thermal Expansion and Intrinsically Low Thermal Conductivity journal December 2018
Thermoelectric GeTe with Diverse Degrees of Freedom Having Secured Superhigh Performance journal February 2019
Superior performance and high service stability for GeTe-based thermoelectric compounds journal April 2019
Promising cubic MnGeTe2 thermoelectrics journal August 2018
Realizing a stable high thermoelectric zT ∼ 2 over a broad temperature range in Ge 1−x−y Ga x Sb y Te via band engineering and hybrid flash-SPS processing journal January 2019
Discovery of low-temperature GeTe-based thermoelectric alloys with high performance competing with Bi 2 Te 3 journal January 2020
Temperature dependent Raman of BiTe nanotubes journal December 2018
Promising and Eco‐Friendly Cu 2 X‐Based Thermoelectric Materials: Progress and Applications journal January 2020
Advances in thermoelectrics journal April 2018
Eutectoid nano-precipitates inducing remarkably enhanced thermoelectric performance in (Sn 1−x Cd x Te) 1−y (Cu 2 Te) y journal January 2020
Discordant nature of Cd in GeTe enhances phonon scattering and improves band convergence for high thermoelectric performance journal January 2020
High-performance electron-doped GeMnTe 2 : hierarchical structure and low thermal conductivity journal January 2019
Phase Transition Engineering of Cu 2 S to Widen the Temperature Window of Improved Thermoelectric Performance journal July 2019
Regulation of the Crystal Structure Leading to the Bandgap Widening and Phonon Scattering Increasing in Cu 3 SnS 4 ‐Cu 3 SbSe 3 Chalcogenides journal July 2019
Band engineering, carrier density control, and enhanced thermoelectric performance in multi-doped SnTe journal September 2019

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