Enhanced thermoelectric performance of a chimney-ladder (Mn 1-xCr x )Si γ (γ∼ 1:7) solid solution

Yuta Kikuchi, Yuzuru Miyazaki, Yoshitsugu Saito, Kei Hayashi, Kunio Yubuta, Tsuyoshi Kajitani

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29 Citations (Scopus)

Abstract

A partially Cr-substituted solid solution of a higher manganese silicide, (Mn 1-x Cr x )Si γ, has been prepared by an arc-melting method and a subsequent annealing process. The compound consists of two tetragonal subsystems of [Mn 1-x Cr x ] and [Si] with an irrational c-axis ratio, γ = c Mn/c Si. According to Vegard's rule, the solubility limit of Cr is determined at x = 0:20. With increasing Cr content x from 0 to 0.20, equivalent to increasing the hole carrier concentration, the a- and cMn-axis lengths linearly increase, while the cSi-axis length gradually decreases. As expected from a valence electron counting rule, the electrical conductivity of (Mn 1-x Cr x )Si γ increases with increasing x from 334 S·cm -1 (x = 0) to 727 S·cm -1 (x = 0.20) at room temperature. The Cr-substituted samples undergo a microscale domain separation; the sample with a nominal composition of x = 0.20 consists of Cr-rich (x ∼ 0:3) and Mn-rich (x ∼ 0:1) dendritic domains with a typical size of ∼100 μm. Despite the substantial increase in electrical conductivity, the total thermal conductivity decreases with increasing x owing to a marked reduction in lattice contribution. As a consequence, the dimensionless figure-of-merit ZT increases from 0.28 (x = 0) at 800 K to 0.45 (x = 0.20) at 900 K.

Original languageEnglish
Article number085801
JournalJapanese journal of applied physics
Volume51
Issue number8 PART 1
DOIs
Publication statusPublished - 2012 Aug 1

ASJC Scopus subject areas

  • Engineering(all)
  • Physics and Astronomy(all)

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