A first-principles approach to half-Heusler thermoelectrics: Accelerated prediction and understanding of material properties

Page, Alexander; Poudeu, Pierre F. P.; Uher, Ctirad

doi:10.1016/j.jmat.2016.04.006

Cited by 67 publications

(31 citation statements)

References 47 publications

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“…In bulk materials, bandstructures can be manipulated to achieve this by applying strain, doping, alloying, and second phasing with other suitable structures [7][8][9] . For example, half-Heusler (HH) alloys [10][11][12][13][14] have complex bandstructures with the potential for beneficial band convergence.…”

Section: Introductionmentioning

confidence: 99%

Thermoelectric Power Factor Under Strain-Induced Band-Alignment in the Half-Heuslers NbCoSn and TiCoSb

Kumarasinghe

Neophytou

2020

Theory and Simulation in Physics for Materials Applications

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Band convergence is an effective strategy to improve the thermoelectric performance of complex bandstructure thermoelectric materials. Half-Heuslers are good candidates for band convergence studies because they have multiple bands near the valence bad edge that can be converged through various band engineering approaches providing power factor improvement opportunities. Theoretical calculations to identify the outcome of band convergence employ various approximations for the carrier scattering relaxation times (the most common being the constant relaxation time approximation) due to the high computational complexity involved in extracting them accurately. Here, we compare the outcome of strain-induced band convergence under two such scattering scenarios: i) the most commonly used constant relaxation time approximation and ii) energy dependent inter-and intra-valley scattering considerations for the half-Heuslers NbCoSn and TiCoSb. We show that the outcome of band convergence on the power factor depends on the carrier scattering assumptions, as well as the temperature. For both materials examined, band convergence improves the power factor. For NbCoSn, however, band convergence becomes more beneficial as temperature increases, under both scattering relaxation time assumptions. In the case of TiCoSb, on the other hand, constant relaxation time considerations also indicate that the relative power factor improvement increases with temperature, but under the energy dependent scattering time considerations, 2 the relative improvement weakens with temperature. This indicates that the scattering details need to be accurately considered in band convergence studies to predict more accurate trends.

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Section: Introductionmentioning

confidence: 99%

Thermoelectric Power Factor Under Strain-Induced Band-Alignment in the Half-Heuslers NbCoSn and TiCoSb

Kumarasinghe

Neophytou

2020

Theory and Simulation in Physics for Materials Applications

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“…One possible way to optimize zT is to maximize the power factor ( α 2 σ ), which can be achieved by the band engineering [ 2 ]. The band structure is one of the basic characteristics of materials, as well as the vital tool in understanding, optimizing, and even designing novel functional materials [ 3 ]. Once the electronic structure calculation is done, the electrical transport properties can be effectively tuned according to the band structure–related parameters.…”

Section: Introductionmentioning

confidence: 99%

Band Structures and Transport Properties of High-Performance Half-Heusler Thermoelectric Materials by First Principles

2018

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Half-Heusler (HH) compounds, with a valence electron count of 8 or 18, have gained popularity as promising high-temperature thermoelectric (TE) materials due to their excellent electrical properties, robust mechanical capabilities, and good high-temperature thermal stability. With the help of first-principles calculations, great progress has been made in half-Heusler thermoelectric materials. In this review, we summarize some representative theoretical work on band structures and transport properties of HH compounds. We introduce how basic band-structure calculations are used to investigate the atomic disorder in n-type MNiSb (M = Ti, Zr, Hf) compounds and guide the band engineering to enhance TE performance in p-type FeRSb (R = V, Nb) based systems. The calculations on electrical transport properties, especially the scattering time, and lattice thermal conductivities are also demonstrated. The outlook for future research directions of first-principles calculations on HH TE materials is also discussed.

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“…We should note, however, that the configurational entropy of the HH alloy, which is totally neglected in Eq. (4), will always contribute favourably to the free energy and enhance the chemical stability of the XY Z compound at finite temperatures [39,40]. Consequently, a positive but small value of E mix does not necessarily imply phase separation under realistic T = 0 K conditions.…”

Section: Magnetism and Mixing Stabilitymentioning

confidence: 99%

First-principles prediction of magnetically ordered half-metals above room temperature

Sattar

Ahmad

Hussain

et al. 2019

Journal of Materiomics

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Half-metallicity (HM) offers great potential for engineering spintronic applications, yet only few magnetic materials present metallicity in just one spin channel. In addition, most HM systems become magnetically disordered at temperatures well below ambient conditions, which further hinders the development of spin-based electronic devices. Here, we use first-principles methods based on density functional theory (DFT) to investigate the electronic, magnetic, structural, mixing, and vibrational properties of 90 XY Z half-Heusler (HH) alloys (X = Li, Na, K, Rb, Cs; Y = V, Nb, Ta; Z = Si, Ge, Sn, S, Se, Te). We disclose a total of 28 new HH compounds that are ferromagnetic, vibrationally stable, and HM, with semiconductor band gaps in the range of 1-4 eV and HM band gaps of 0.2-0.8 eV. By performing Monte Carlo simulations of a spin Heisenberg model fitted to DFT energies, we estimate the Curie temperature, TC, of each HM compound. We find that 17 HH HM remain magnetically ordered at and above room temperature, namely, 300 ≤ TC ≤ 450 K, with total magnetic moments of 2 and 4 µB. A further materials sieve based on zero-temperature mixing energies let us to conclude 5 overall promising ferromagnetic HH HM at and above room temperature: NaVSi, RbVTe, CsVS, CsVSe, and RbNbTe. We also predict 2 ferromagnetic materials that are semiconductor and magnetically ordered at ambient conditions: LiVSi and LiVGe. arXiv:1812.04813v1 [cond-mat.mtrl-sci]

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A first-principles approach to half-Heusler thermoelectrics: Accelerated prediction and understanding of material properties

Cited by 67 publications

References 47 publications

Thermoelectric Power Factor Under Strain-Induced Band-Alignment in the Half-Heuslers NbCoSn and TiCoSb

Thermoelectric Power Factor Under Strain-Induced Band-Alignment in the Half-Heuslers NbCoSn and TiCoSb

Band Structures and Transport Properties of High-Performance Half-Heusler Thermoelectric Materials by First Principles

First-principles prediction of magnetically ordered half-metals above room temperature

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