Impact of Nb vacancies and p-type doping of the NbCoSn-NbCoSb half-Heusler thermoelectrics

Daniella Ferluccio, Ronald I. Smith, Jim Buckman, Jan-Willem G. Bos

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Abstract

The half-Heuslers NbCoSn and NbCoSb have promising thermoelectric properties. Here, an investigation of the NbCo1+ySn1-zSbz (y = 0, 0.05; 0 ≤ z ≤ 1) solid-solution is presented. In addition, the p-type doping of NbCoSn using Ti and Zr substitution is investigated. Rietveld analysis reveals the gradual creation of Nb vacancies to compensate for the n-type doping caused by the substitution of Sb in NbCoSn. This leads to a similar valence electron count (~18.25) for the NbCo1+ySn1-zSbz samples (z > 0). The mass fluctuation disorder due to the Nb vacancies strongly decreases the lattice thermal conductivity from 10 W m-1 K-1 (z = 0) to 4.5 W m-1 K-1 (z = 0.5, 1). This is accompanied by a transition to degenerate semiconducting behaviour leading to large power factors, S2/ρ = 2.5-3 mW m-1 K-2 and figures of merit, ZT = 0.25-0.33 at 773 K. Ti and Zr can be used to achieve positive Seebeck values, e.g. S = +150 μV K-1 for 20% Zr at 773 K. However, the electrical resistivity, ρ323K = 27-35 m cm, remains too large for these materials to be considered useful p-type materials.
LanguageEnglish
Pages3979-3987
Number of pages9
JournalPhysical Chemistry Chemical Physics
Volume20
Issue number6
Early online date5 Jan 2018
DOIs
Publication statusPublished - 14 Feb 2018

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title = "Impact of Nb vacancies and p-type doping of the NbCoSn-NbCoSb half-Heusler thermoelectrics",
abstract = "The half-Heuslers NbCoSn and NbCoSb have promising thermoelectric properties. Here, an investigation of the NbCo1+ySn1-zSbz (y = 0, 0.05; 0 ≤ z ≤ 1) solid-solution is presented. In addition, the p-type doping of NbCoSn using Ti and Zr substitution is investigated. Rietveld analysis reveals the gradual creation of Nb vacancies to compensate for the n-type doping caused by the substitution of Sb in NbCoSn. This leads to a similar valence electron count (~18.25) for the NbCo1+ySn1-zSbz samples (z > 0). The mass fluctuation disorder due to the Nb vacancies strongly decreases the lattice thermal conductivity from 10 W m-1 K-1 (z = 0) to 4.5 W m-1 K-1 (z = 0.5, 1). This is accompanied by a transition to degenerate semiconducting behaviour leading to large power factors, S2/ρ = 2.5-3 mW m-1 K-2 and figures of merit, ZT = 0.25-0.33 at 773 K. Ti and Zr can be used to achieve positive Seebeck values, e.g. S = +150 μV K-1 for 20{\%} Zr at 773 K. However, the electrical resistivity, ρ323K = 27-35 m cm, remains too large for these materials to be considered useful p-type materials.",
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Impact of Nb vacancies and p-type doping of the NbCoSn-NbCoSb half-Heusler thermoelectrics. / Ferluccio, Daniella; Smith, Ronald I.; Buckman, Jim; Bos, Jan-Willem G.

In: Physical Chemistry Chemical Physics, Vol. 20, No. 6, 14.02.2018, p. 3979-3987.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Impact of Nb vacancies and p-type doping of the NbCoSn-NbCoSb half-Heusler thermoelectrics

AU - Ferluccio, Daniella

AU - Smith, Ronald I.

AU - Buckman, Jim

AU - Bos, Jan-Willem G.

PY - 2018/2/14

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N2 - The half-Heuslers NbCoSn and NbCoSb have promising thermoelectric properties. Here, an investigation of the NbCo1+ySn1-zSbz (y = 0, 0.05; 0 ≤ z ≤ 1) solid-solution is presented. In addition, the p-type doping of NbCoSn using Ti and Zr substitution is investigated. Rietveld analysis reveals the gradual creation of Nb vacancies to compensate for the n-type doping caused by the substitution of Sb in NbCoSn. This leads to a similar valence electron count (~18.25) for the NbCo1+ySn1-zSbz samples (z > 0). The mass fluctuation disorder due to the Nb vacancies strongly decreases the lattice thermal conductivity from 10 W m-1 K-1 (z = 0) to 4.5 W m-1 K-1 (z = 0.5, 1). This is accompanied by a transition to degenerate semiconducting behaviour leading to large power factors, S2/ρ = 2.5-3 mW m-1 K-2 and figures of merit, ZT = 0.25-0.33 at 773 K. Ti and Zr can be used to achieve positive Seebeck values, e.g. S = +150 μV K-1 for 20% Zr at 773 K. However, the electrical resistivity, ρ323K = 27-35 m cm, remains too large for these materials to be considered useful p-type materials.

AB - The half-Heuslers NbCoSn and NbCoSb have promising thermoelectric properties. Here, an investigation of the NbCo1+ySn1-zSbz (y = 0, 0.05; 0 ≤ z ≤ 1) solid-solution is presented. In addition, the p-type doping of NbCoSn using Ti and Zr substitution is investigated. Rietveld analysis reveals the gradual creation of Nb vacancies to compensate for the n-type doping caused by the substitution of Sb in NbCoSn. This leads to a similar valence electron count (~18.25) for the NbCo1+ySn1-zSbz samples (z > 0). The mass fluctuation disorder due to the Nb vacancies strongly decreases the lattice thermal conductivity from 10 W m-1 K-1 (z = 0) to 4.5 W m-1 K-1 (z = 0.5, 1). This is accompanied by a transition to degenerate semiconducting behaviour leading to large power factors, S2/ρ = 2.5-3 mW m-1 K-2 and figures of merit, ZT = 0.25-0.33 at 773 K. Ti and Zr can be used to achieve positive Seebeck values, e.g. S = +150 μV K-1 for 20% Zr at 773 K. However, the electrical resistivity, ρ323K = 27-35 m cm, remains too large for these materials to be considered useful p-type materials.

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