Thermoelectric Properties and n- to p-Type Conversion of Co-Doped ZrNiSn-Based Half-Heusler Alloys

Xie, Hanhui; Yu, Chengtao; He, Bin; Zhu, Tiejun; Zhao, Xinbing

doi:10.1007/s11664-012-2077-7

Cited by 21 publications

(9 citation statements)

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“…Thermoelectric (TE) materials can undergo a direct conversion between heat and electricity and vice versa via the Seebeck and Peltier effects, with the advantages such as the absence of emissions, absence of moving parts, high reliability, and long life span. − Therefore, thermoelectricity can play an important role in solving the energy and environmental crisis. The performance of TE materials can be evaluated by the dimensionless TE figure-of-merit defined as ZT = T α 2 σ/κ, where α, σ, κ, and T are the Seebeck coefficient, electrical conductivity, thermal conductivity, and absolute temperature, respectively. , In the past few decades, immense efforts have been devoted to improving the TE properties and developing high-performance TE materials through doping and electronic band structure manipulations and forming solid solutions and introducing nanostructural features in the crystal lattice to enhance phonon scattering and thus lower the thermal conductivity. − Despite much improved TE performance of the state-of-the-art TE materials, such as Bi 2 Te 3 , , CoSb 3 , , PbTe, , GeTe, , and half-Heusler alloys, , their large-scale commercial applications have not yet materialized because most of them contain expensive, low-abundant, and often toxic heavy metal elements. Consequently, it is essential to explore new, more environmentally friendly, and cost-effective high-performance TE materials to be competitive and make an impact on large-scale energy conversion applications.…”

Section: Introductionmentioning

confidence: 99%

“…6,7 In the past few decades, immense efforts have been devoted to improving the TE properties and developing high-performance TE materials through doping and electronic band structure manipulations and forming solid solutions and introducing nanostructural features in the crystal lattice to enhance phonon scattering and thus lower the thermal conductivity. 8−13 Despite much improved TE performance of the state-of-the-art TE materials, such as Bi 2 Te 3 , 14,15 CoSb 3 , 16,17 PbTe, 18,19 GeTe, 20,21 and half-Heusler alloys, 22,23 their largescale commercial applications have not yet materialized because most of them contain expensive, low-abundant, and often toxic heavy metal elements. Consequently, it is essential to explore new, more environmentally friendly, and cost-effective highperformance TE materials to be competitive and make an impact on large-scale energy conversion applications.…”

Section: Introductionmentioning

confidence: 99%

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Modification of Bulk Heterojunction and Cl Doping for High-Performance Thermoelectric SnSe₂/SnSe Nanocomposites

Shu

Xie

et al. 2018

ACS Appl. Mater. Interfaces

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SnSe is a wide band gap semiconductor ( E = 1.05 eV) with a typical two-dimensional hexagonal crystal structure of the prototype CdI phase, resulting in an intrinsically low thermal conductivity, which is favorable for thermoelectrics. Herein, we reported the remarkable role of Cl doping in SnSe/SnSe nanocomposites. Doping with Cl in the system not only increases the carrier concentration by an order of magnitude, but it also modifies the heterojunction from that of the Schottky junction type (p-n junction) in undoped samples to junctions having an ohmic contact (n-n junction) when the samples are doped with Cl, increasing their carrier mobility in the process. On account of the simultaneously boosted carrier concentration and carrier mobility upon Cl doping, the electrical conductivity and the power factor are greatly increased. Moreover, the enhanced point defect phonon scattering induced by Cl doping, coupled with the interface phonon scattering, results in a suppression of the thermal conductivity. As a consequence, the maximum ZT value of 0.56 at 773 K is achieved in the 6% Cl-doped SnSe/SnSe nanocomposite measured in the direction parallel to the pressing direction. This is an almost 6 times larger value than that measured on the undoped composite. In addition, unlike the conventional layered compounds (BiTe and SnSe), the ZT value measured parallel to the pressing direction is much higher than the one measured perpendicular to the pressing direction. This study provides a new way for optimizing the thermoelectric properties of materials through interface regulation.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modification of Bulk Heterojunction and Cl Doping for High-Performance Thermoelectric SnSe₂/SnSe Nanocomposites

Shu

Xie

et al. 2018

ACS Appl. Mater. Interfaces

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“…For example, multiple authors have studied the substitution of Ni by Co and demonstrated that a conversion from n-to p-type behavior for the XNiSn system could be achieved. 22,23 Likewise, Horyn et al 24 studied the effects of substituting Sc for Ti or Zr up to 350 K; the resulting compounds showed promising positive thermopower at room temperature.…”

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confidence: 99%

Resolving the true band gap of ZrNiSn half-Heusler thermoelectric materials

et al. 2015

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N-type XNiSn (X ¼ Ti, Zr, Hf) half-Heusler (HH) compounds possess excellent thermoelectric properties, which are believed to be attributed to their relatively high mobility. However, p-type XNiSn HH compounds have poor figures of merit, zT, compared to XCoSb compounds. This can be traced to the suppression of the magnitude of the thermopower at high temperatures. E g ¼ 2eS max T max relates the band gap to the thermopower peak.However, from this formula, one would conclude that the band gap of p-type XNiSn solid solutions is only one-third that of n-type XNiSn, which effectively prevents p-type XNiSn HHs from being useful thermoelectric materials. The study of p-type HH Zr 1Àx Sc x NiSn solid solutions show that the large mobility difference between electrons and holes in XNiSn results in a significant correction to the Goldsmid-Sharp formula. This finding explains the difference in the thermopower band gap between n-type and p-type HH. The high electron-to-hole weighted mobility ratio leads to an effective suppression of the bipolar effect in the thermoelectric transport properties which is essential for high zT values in n-type XNiSn (X ¼ Ti, Zr, Hf) HH compounds.

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“…The higher the carrier concentration, the higher is the temperature at which the overcompensation occurs. Experimentally, electron dominated thermoelectric response has been reported for XNiSn alloys [6][7][8]28] but not for XCoSb alloys. The bandgap of XCoSb alloys is larger than that of XNiSn alloys (despite the same crystal structure) so that the temperature at which bipolar conduction occurs is higher.…”

Section: Resultsmentioning

confidence: 99%

Thermoelectric Properties of the XCoSb (X: Ti,Zr,Hf) Half‐Heusler alloys

Gandi

Schwingenschlögl

2017

Physica Status Solidi (b)

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We investigate the thermoelectric properties of the half‐Heusler alloys XCoSb (X: Ti,Zr,Hf) by solving Boltzmann transport equations and discuss them in terms of the electronic band structure. The rigid band approximation is employed to address the effects of doping. While many half‐Heuser alloys show excellent thermoelectric performance, the materials under study are special by supporting both n‐ and p‐doping. We identify the reasons for this balanced thermoelectric transport and explain why experimentally p‐doping is superior to n‐doping. We also determine the spectrum of phonon mean free paths to guide grain refinement methods to enhance the thermoelectric figure of merit.

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Thermoelectric Properties and n- to p-Type Conversion of Co-Doped ZrNiSn-Based Half-Heusler Alloys

Cited by 21 publications

References 21 publications

Modification of Bulk Heterojunction and Cl Doping for High-Performance Thermoelectric SnSe₂/SnSe Nanocomposites

Modification of Bulk Heterojunction and Cl Doping for High-Performance Thermoelectric SnSe₂/SnSe Nanocomposites

Resolving the true band gap of ZrNiSn half-Heusler thermoelectric materials

Thermoelectric Properties of the XCoSb (X: Ti,Zr,Hf) Half‐Heusler alloys

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Thermoelectric Properties and n- to p-Type Conversion of Co-Doped ZrNiSn-Based Half-Heusler Alloys

Cited by 21 publications

References 21 publications

Modification of Bulk Heterojunction and Cl Doping for High-Performance Thermoelectric SnSe2/SnSe Nanocomposites

Modification of Bulk Heterojunction and Cl Doping for High-Performance Thermoelectric SnSe2/SnSe Nanocomposites

Resolving the true band gap of ZrNiSn half-Heusler thermoelectric materials

Thermoelectric Properties of the XCoSb (X: Ti,Zr,Hf) Half‐Heusler alloys

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Modification of Bulk Heterojunction and Cl Doping for High-Performance Thermoelectric SnSe₂/SnSe Nanocomposites

Modification of Bulk Heterojunction and Cl Doping for High-Performance Thermoelectric SnSe₂/SnSe Nanocomposites