The role of simultaneous substitution of Cr and Ru on the thermoelectric properties of defect manganese silicides MnSiδ (1.73 <δ <1.75)

V. Ponnambalam, Donald T. Morelli, S. Bhattacharya, Terry M. Tritt

Research output: Contribution to journalArticle

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Abstract

Defect manganese silicides have been substituted with Cr and Ru, in order to study the role of these substitutions on the resulting resistivity (q), Seebeck (a) and Hall coefficients and thermal conductivity. The resistivity and Seebeck coefficient measurements suggest that these compounds are degenerate semiconductors. The Hall measurements indicate that the carrier concentration increases in Cr and Ru substituted compounds. The majority carriers are holes and the change of hole concentration is only marginal. While the hole concentration (p) of MnSi1.74 is ∼ 2.1 × 1021 cm -3, in heavily substituted Mn0.65Cr0.2Ru0.15Si1.74, p increases only to ∼4.5 × 1021 cm -3. The increase in p is presumably due to Si precipitation. One interesting feature is the low lattice thermal conductivity (jL) which is 2-2.5 W/m K at 300 K depending upon the composition. In addition, jL shows a weak temperature dependence. Because of the combination of high power factor (a2/q) 2 mW/m K2 and low thermal conductivity 2.5-2.7 W/m K, Mn0.95Cr0.5Si1.74 and Mn0.97Cr0.3Si1.74 exhibit highest ZT of 0.6 at 850 K. For other compounds, a moderate ZT value of 0.3-0.5 is realized at 850 K. In Ru substituted compounds, the ZT is not improved beyond 0.5, due to the decrease of charge carrier mobility.

LanguageEnglish (US)
Pages598-603
Number of pages6
JournalJournal of Alloys and Compounds
Volume580
DOIs
StatePublished - 2013

Profile

Silicides
Manganese
Hole concentration
Thermal conductivity
Substitution reactions
Defects
Seebeck coefficient
Carrier mobility
Charge carriers
Carrier concentration
Semiconductor materials
Chemical analysis
Temperature

Keywords

  • Hall coefficient
  • Higher manganese silicides
  • Resistivity
  • Seebeck coefficient
  • Thermoelectrics

ASJC Scopus subject areas

  • Mechanical Engineering
  • Mechanics of Materials
  • Materials Chemistry
  • Metals and Alloys

Cite this

The role of simultaneous substitution of Cr and Ru on the thermoelectric properties of defect manganese silicides MnSiδ (1.73 <δ <1.75). / Ponnambalam, V.; Morelli, Donald T.; Bhattacharya, S.; Tritt, Terry M.

In: Journal of Alloys and Compounds, Vol. 580, 2013, p. 598-603.

Research output: Contribution to journalArticle

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AB - Defect manganese silicides have been substituted with Cr and Ru, in order to study the role of these substitutions on the resulting resistivity (q), Seebeck (a) and Hall coefficients and thermal conductivity. The resistivity and Seebeck coefficient measurements suggest that these compounds are degenerate semiconductors. The Hall measurements indicate that the carrier concentration increases in Cr and Ru substituted compounds. The majority carriers are holes and the change of hole concentration is only marginal. While the hole concentration (p) of MnSi1.74 is ∼ 2.1 × 1021 cm -3, in heavily substituted Mn0.65Cr0.2Ru0.15Si1.74, p increases only to ∼4.5 × 1021 cm -3. The increase in p is presumably due to Si precipitation. One interesting feature is the low lattice thermal conductivity (jL) which is 2-2.5 W/m K at 300 K depending upon the composition. In addition, jL shows a weak temperature dependence. Because of the combination of high power factor (a2/q) 2 mW/m K2 and low thermal conductivity 2.5-2.7 W/m K, Mn0.95Cr0.5Si1.74 and Mn0.97Cr0.3Si1.74 exhibit highest ZT of 0.6 at 850 K. For other compounds, a moderate ZT value of 0.3-0.5 is realized at 850 K. In Ru substituted compounds, the ZT is not improved beyond 0.5, due to the decrease of charge carrier mobility.

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