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Crystal structure and thermoelectric properties of the incommensurate chimney–ladder compound RhGeγ (γ ∼ 1.293)

Published online by Cambridge University Press:  01 June 2015

Yuzuru Miyazaki ,
Takaki Nakajo ,
Yuta Kikuchi  and
Kei Hayashi
Yuzuru Miyazaki*
Affiliation:
Department of Applied Physics, Graduate School of Engineering, Tohoku University, Aoba-ku, Sendai 980-8579, Japan
Takaki Nakajo
Affiliation:
Department of Applied Physics, Graduate School of Engineering, Tohoku University, Aoba-ku, Sendai 980-8579, Japan
Yuta Kikuchi
Affiliation:
Department of Applied Physics, Graduate School of Engineering, Tohoku University, Aoba-ku, Sendai 980-8579, Japan
Kei Hayashi
Affiliation:
Department of Applied Physics, Graduate School of Engineering, Tohoku University, Aoba-ku, Sendai 980-8579, Japan
*
a)Address all correspondence to this author. e-mail: miya@crystal.apph.tohoku.ac.jp
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Abstract

The (3 + 1)-dimensional crystal structure of the Nowotny chimney–ladder compound Rh17Ge22 was revealed using powder x-ray diffraction technique. As in the case of the higher manganese silicide MnSiγ (known as Mn11Si19, etc.), this germanide consists of two tetragonal subsystems of [Rh] and [Ge] with an irrational c-axis ratio γ = cRh/cGe, and hence the structural formula can be represented as RhGeγ. As expected from first-principles calculations of the approximate structure and the valence electron count, n-type (negative Seebeck coefficient) conduction was experimentally confirmed over the whole temperature range of 333–984 K. Although the absolute value of the Seebeck coefficient was limited to |S| ≤ 53 μV/K, a high electrical conductivity (σ = 4.8 × 103 S/cm) yielded a reasonable power factor of S2σ ∼ 1 mW/K2 m above 600 K. A maximum dimensionless figure-of-merit of ∼0.1 at 900 K was expected using thermal conductivity data of a sintered pellet.

Keywords

thermoelectricitycrystallographic structureelectronic structure
Type
Invited Article
Information
Journal of Materials Research , Volume 30 , Issue 17: Focus Issue: Advances in Thermoelectric Materials II , 14 September 2015 , pp. 2611 - 2617
Copyright
Copyright © Materials Research Society 2015 

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References

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