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Higher manganese silicides (denoted as MnSiγ) are a prominent class of intermetallic compound for thermoelectric applications that crystallizes into a Nowotny Chimney Ladder (NCL) phase and constitutes a higher concentration of silicon with odd stoichiometry typically represented by an irrational number. In this work, we present the genesis of Si odd stoichiometry and secondary phase relations in silicon-rich and silicon-deficient MnSix to present the significance of labile (i.e., easily alterable) Si-subsystem in inheriting the modulated lattice structure with characteristic anharmonicity as found using density functional theory-based phonon calculation in Mn4Si7, a representative commensurate structure. The transport properties show an interrelation to the presence of a secondary phase, which is driven by the odd stoichiometry, where the thermoelectric figure of merit is found to be optimal for MnSi1.74. The structural characterization of rapidly solidified melt-spun ribbons and spark plasma sintered bulk specimens reveal a characteristic presence of MnSi and Si as secondary phases in Si-deficient (x ~ 1.5) and Si-excess (x ~ 2) compositions of nominal MnSix, respectively that coexists with the major MnSiγ based NCL phase. This study provides the fundamental basis of phase evolution and the relevance of odd stoichiometry in silicon-rich manganese silicides which exhibits fascinating phonon dynamics in optimal MnSi1.74 stoichiometry.

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  This is the pre-peer reviewed version of the following article: N. S. Chauhan, S. G. Sara, A. Bhattacharya, T. Mori, Y. Miyazaki, Odd-Stoichiometry and Secondary Phase Relations in Higher Manganese Silicides. Adv. Funct. Mater. 2024, 34, 2313948., which has been published in final form at https://doi.org/10.1002/adfm.202313948. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.

Keyword: thermoelectric

Date published: 2024-01-02

Publisher: Wiley

Journal:

• Advanced Functional Materials (ISSN: 16163028) vol. 34 issue. 17 2313948

Funding:

• Japan Society for the Promotion of Science 22H04580

Manuscript type: Author's original (Submitted manuscript)

MDR DOI: https://doi.org/10.48505/nims.4807

First published URL: https://doi.org/10.1002/adfm.202313948

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Updated at: 2024-10-08 16:30:39 +0900

Published on MDR: 2024-10-08 16:30:39 +0900