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Issue 40, 2015
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MoSi2-type narrow band gap intermetallic compound Al6Re5Si4 as a thermoelectric material

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Abstract

The thermoelectric properties of MoSi2-type intermetallic compound Al6Re5Si4 (investigated compositions: Al6−xRe4.7Si4+x (x = 0–0.9)) related to TiSi2-type narrow band gap intermetallic compounds were systematically investigated. A first-principles band structure calculation implies that this compound forms a narrow band gap in the electronic density of states that will be suitable for obtaining a large power factor. Indeed, the maximum power factor is 1.65 mW m−1 K−2 for the sample with x = 0.8. The Al6−xRe4.7Si4+x (x = 0–0.8) samples show degenerate semiconductor behavior as p-type materials; the temperature coefficient of the electrical conductivity is negative and the positive Seebeck coefficient increases with increasing temperature. A negative Seebeck coefficient is observed in the Si-rich sample with x = 0.9, which is understood by shifting the Fermi level to the conduction band. The estimated band gap is 0.53 eV from the Arrhenius plot. Because of a simple crystal structure, a relatively high thermal conductivity ranging from 7.6 to 13.5 W m−1 K−1 is observed at 300 K. The maximum dimensionless figure-of-merit of 0.19 at 973 K is close to the optimal value predicted by a single parabolic band model.

Graphical abstract: MoSi2-type narrow band gap intermetallic compound Al6Re5Si4 as a thermoelectric material

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Publication details

The article was received on 03 Jun 2015, accepted on 23 Jun 2015 and first published on 07 Jul 2015


Article type: Paper
DOI: 10.1039/C5TC01608H
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Citation: J. Mater. Chem. C, 2015,3, 10422-10429
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    MoSi2-type narrow band gap intermetallic compound Al6Re5Si4 as a thermoelectric material

    Y. Takagiwa, S. Utada, I. Kanazawa and K. Kimura, J. Mater. Chem. C, 2015, 3, 10422
    DOI: 10.1039/C5TC01608H

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