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Issue 32, 2019
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Layered manganese bismuth tellurides with GeBi4Te7- and GeBi6Te10-type structures: towards multifunctional materials

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Abstract

The crystal structures of new layered manganese bismuth tellurides with the compositions Mn0.85(3)Bi4.10(2)Te7 and Mn0.73(4)Bi6.18(2)Te10 were determined by single-crystal X-ray diffraction, including the use of microfocused synchrotron radiation. These analyses reveal that the layered structures deviate from the idealized stoichiometry of the 12P-GeBi4Te7 (space group P[3 with combining macron]m1) and 51R-GeBi6Te10 (space group R[3 with combining macron]m) structure types they adopt. Modified compositions Mn1−xBi4+2x/3Te7 (x = 0.15–0.2) and Mn1−xBi6+2x/3Te10 (x = 0.19–0.26) assume cation vacancies and lead to homogenous bulk samples as confirmed by Rietveld refinements. Electron diffraction patterns exhibit no diffuse streaks that would indicate stacking disorder. The alternating quintuple-layer [M2Te3] and septuple-layer [M3Te4] slabs (M = mixed occupied by Bi and Mn) with 1 : 1 sequence (12P stacking) in Mn0.85Bi4.10Te7 and 2 : 1 sequence (51R stacking) in Mn0.81Bi6.13Te10 were also observed in HRTEM images. Temperature-dependent powder diffraction and differential scanning calorimetry show that the compounds are high-temperature phases, which are metastable at ambient temperature. Magnetization measurements are in accordance with a MnII oxidation state and point at predominantly ferromagnetic coupling in both compounds. The thermoelectric figures of merit of n-type conducting Mn0.85Bi4.10Te7 and Mn0.81Bi6.13Te10 reach zT = 0.25 at 375 °C and zT = 0.28 at 325 °C, respectively. Although the compounds are metastable, compact ingots exhibit still up to 80% of the main phases after thermoelectric measurements up to 400 °C.

Graphical abstract: Layered manganese bismuth tellurides with GeBi4Te7- and GeBi6Te10-type structures: towards multifunctional materials

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Supplementary files

Article information


Submitted
19 Feb 2019
Accepted
18 Jul 2019
First published
18 Jul 2019

This article is Open Access

J. Mater. Chem. C, 2019,7, 9939-9953
Article type
Paper

Layered manganese bismuth tellurides with GeBi4Te7- and GeBi6Te10-type structures: towards multifunctional materials

D. Souchay, M. Nentwig, D. Günther, S. Keilholz, J. de Boor, A. Zeugner, A. Isaeva, M. Ruck, A. U. B. Wolter, B. Büchner and O. Oeckler, J. Mater. Chem. C, 2019, 7, 9939
DOI: 10.1039/C9TC00979E

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