Isovalent substitutes play in different ways: Effects of isovalent substitution on the thermoelectric properties of CoSi0.98B0.02

Hui Sun, Xu Lu, Donald T. Morelli

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Abstract

Boron-added CoSi, CoSi0.98B0.02, possesses a very high thermoelectric power factor of 60 μW cm-1 K-2 at room temperature, which is among the highest power factors that have ever been reported for near-room-temperature thermoelectric applications. Since the electrical properties of this material have been tuned properly, isovalent substitution for its host atoms is intentionally employed to reduce the lattice thermal conductivity while maintaining the electronic properties unchanged. In our previous work, the effect of Rh substitution for Co atoms on the thermoelectric properties of CoSi0.98B0.02 has been studied. Here, we present a study of the substitution of Ge for Si atoms in this compound. Even though Ge and Rh are isovalent with their corresponding host atoms, they play different roles in determining the electrical and thermal transport properties. Through the evaluation of the lattice thermal conductivity by the Debye approximation and the comparison between the high-temperature Seebeck coefficients, we propose that Rh substitution leads to a further overlapping of the conduction and the valence bands, while Ge substitution only shifts the Fermi level upward into the conduction band. Our results show that the influence of isovalent substitution on the electronic structure cannot be ignored when the alloying method is used to improve thermoelectric properties.

LanguageEnglish (US)
Article number035107
JournalJournal of Applied Physics
Volume120
Issue number3
DOIs
StatePublished - Jul 21 2016

Profile

substitutes
atoms
thermal conductivity
room temperature
Seebeck effect
alloying
conduction bands
boron
transport properties
electrical properties
electronic structure
valence
conduction
evaluation
shift
approximation
electronics

ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

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abstract = "Boron-added CoSi, CoSi0.98B0.02, possesses a very high thermoelectric power factor of 60 μW cm-1 K-2 at room temperature, which is among the highest power factors that have ever been reported for near-room-temperature thermoelectric applications. Since the electrical properties of this material have been tuned properly, isovalent substitution for its host atoms is intentionally employed to reduce the lattice thermal conductivity while maintaining the electronic properties unchanged. In our previous work, the effect of Rh substitution for Co atoms on the thermoelectric properties of CoSi0.98B0.02 has been studied. Here, we present a study of the substitution of Ge for Si atoms in this compound. Even though Ge and Rh are isovalent with their corresponding host atoms, they play different roles in determining the electrical and thermal transport properties. Through the evaluation of the lattice thermal conductivity by the Debye approximation and the comparison between the high-temperature Seebeck coefficients, we propose that Rh substitution leads to a further overlapping of the conduction and the valence bands, while Ge substitution only shifts the Fermi level upward into the conduction band. Our results show that the influence of isovalent substitution on the electronic structure cannot be ignored when the alloying method is used to improve thermoelectric properties.",
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N2 - Boron-added CoSi, CoSi0.98B0.02, possesses a very high thermoelectric power factor of 60 μW cm-1 K-2 at room temperature, which is among the highest power factors that have ever been reported for near-room-temperature thermoelectric applications. Since the electrical properties of this material have been tuned properly, isovalent substitution for its host atoms is intentionally employed to reduce the lattice thermal conductivity while maintaining the electronic properties unchanged. In our previous work, the effect of Rh substitution for Co atoms on the thermoelectric properties of CoSi0.98B0.02 has been studied. Here, we present a study of the substitution of Ge for Si atoms in this compound. Even though Ge and Rh are isovalent with their corresponding host atoms, they play different roles in determining the electrical and thermal transport properties. Through the evaluation of the lattice thermal conductivity by the Debye approximation and the comparison between the high-temperature Seebeck coefficients, we propose that Rh substitution leads to a further overlapping of the conduction and the valence bands, while Ge substitution only shifts the Fermi level upward into the conduction band. Our results show that the influence of isovalent substitution on the electronic structure cannot be ignored when the alloying method is used to improve thermoelectric properties.

AB - Boron-added CoSi, CoSi0.98B0.02, possesses a very high thermoelectric power factor of 60 μW cm-1 K-2 at room temperature, which is among the highest power factors that have ever been reported for near-room-temperature thermoelectric applications. Since the electrical properties of this material have been tuned properly, isovalent substitution for its host atoms is intentionally employed to reduce the lattice thermal conductivity while maintaining the electronic properties unchanged. In our previous work, the effect of Rh substitution for Co atoms on the thermoelectric properties of CoSi0.98B0.02 has been studied. Here, we present a study of the substitution of Ge for Si atoms in this compound. Even though Ge and Rh are isovalent with their corresponding host atoms, they play different roles in determining the electrical and thermal transport properties. Through the evaluation of the lattice thermal conductivity by the Debye approximation and the comparison between the high-temperature Seebeck coefficients, we propose that Rh substitution leads to a further overlapping of the conduction and the valence bands, while Ge substitution only shifts the Fermi level upward into the conduction band. Our results show that the influence of isovalent substitution on the electronic structure cannot be ignored when the alloying method is used to improve thermoelectric properties.

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