Nanoscale structural heterogeneity in Ni-rich half-Heusler TiNiSn

Douglas, Jason E.; Chater, Philip A.; Brown, Craig M.; Pollock, Tresa M.; Seshadri, Ram

doi:10.1063/1.4900497

Cited by 46 publications

(70 citation statements)

References 27 publications

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“…For instance for ZrNiSn, with a defect-pair concentration of 2.9%, κ is reduced to 7.4 W/m/K, and for 4%, it is reduced to [58][59][60], or the related Ni interstitial defects, which may reduce the κ considerably by scattering phonon modes of higher energy [57]. A high solubility of Ni interstitials has been reported [61][62][63][64][65]. The overestimation of κ by theory of the unmixed XNiSn HHs can thus, at least partially, be explained by the presence of localized defects.…”

Section: B Thermal Conductivity In Bulk Xnisnmentioning

confidence: 99%

Lattice thermal conductivity ofTixZryHf1−x−yNiSnhalf-Heusler alloys calculated from first principles: Key role of nature of phonon modes

et al. 2017

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In spite of their relatively high lattice thermal conductivity κ , the XNiSn (X = Ti, Zr, or Hf) half-Heusler compounds are good thermoelectric materials. Previous studies have shown that κ can be reduced by sublattice alloying on the X site. To cast light on how the alloy composition affects κ , we study this system using the phonon Boltzmann-transport equation within the relaxation time approximation in conjunction with density functional theory. The effect of alloying through mass-disorder scattering is explored using the virtual crystal approximation to screen the entire ternary Ti x Zr y Hf 1−x−y NiSn phase diagram. The lowest lattice thermal conductivity is found for the Ti x Hf 1−x NiSn compositions; in particular, there is a shallow minimum centered at Ti 0.5 Hf 0.5 NiSn with κ taking values between 3.2 and 4.1 W/mK when the Ti content varies between 20% and 80%. Interestingly, the overall behavior of mass-disorder scattering in this system can only be understood from a combination of the nature of the phonon modes and the magnitude of the mass variance. Mass-disorder scattering is not effective at scattering acoustic phonons of low energy. By using a simple model of grain boundary scattering, we find that nanostructuring these compounds can scatter such phonons effectively and thus further reduce the lattice thermal conductivity; for instance, Ti 0.5 Hf 0.5 NiSn with a grain size of L = 100 nm experiences a 42% reduction of κ compared to that of the single crystal.

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Section: B Thermal Conductivity In Bulk Xnisnmentioning

confidence: 99%

Lattice thermal conductivity ofTixZryHf1−x−yNiSnhalf-Heusler alloys calculated from first principles: Key role of nature of phonon modes

et al. 2017

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“…These methods have been used in many material systems to examine phase separation and structural heterogeneity. 38,39 Figure 7 illustrates the fit of each model to the main reflection (021) of Sr 0.80 Na 0.20 Pd 3 O 4 . The total Na occupancy was not fixed in either of the models and refined to between 12 % and 16 % total occupancy.…”

Section: Electrical Properties and Electronic Structurementioning

confidence: 99%

The Role of Structural and Compositional Heterogeneities in the Insulator-to-Metal Transition in Hole-Doped APd₃O₄ (A = Ca, Sr)

Lamontagne¹,

Laurita²,

Knight³

et al. 2017

Inorg. Chem.

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The cubic semiconducting compounds APd 3 O 4 (A = Ca, Sr) can be hole-doped by Na substitution on the A site and driven towards more conducting states. This process has been followed here by a number of experimental techniques in order to understand the evolution of electronic properties. While an insulator-to-metal transition is observed in Ca 1−x Na x Pd 3 O 4 for x ≥ 0.15, bulk metallic behavior is not observed for Sr 1−x Na x Pd 3 O 4 up to x = 0.20. Given the very similar crystal and (calculated) electronic structures of the two materials, the distinct behavior is a matter of interest.We present evidence of local disorder in the A = Sr materials through the analysis of the neutron pair distribution function which is potentially at the heart of the distinct behavior. Solid-state 23 Na nuclear magnetic resonance studies additionally suggest a percolative insulator-to-metal transition mechanism wherein presumably small regions with a signal resembling metallic NaPd 3 O 4 form almost immediately upon Na substitution, and this signal grows monotonically with substitution. Some signatures of increased local disorder and a propensity for Na clustering are seen in the A = Sr compounds.

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“…[7] The 24 VEC Heusler compounds such as TiFe 2 Sn and VFe 2 Al are of potential value as thermoelectrics due to relatively small band gaps. Anti-site disorder [8] and other structural defects [9] are characteristic to Heusler compounds, influencing the band structure [10] and electrical properties including the resistivity and Seebeck coefficient.…”

Section: Introductionmentioning

confidence: 99%

Thermoelectric performance and the role of anti-site disorder in the 24-electron Heusler TiFe₂Sn

Buffon

Laurita

Lamontagne

et al. 2017

J. Phys.: Condens. Matter

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Abstract. Heusler compounds XY 2 Z with 24 valence electrons per formula unit are potential thermoelectric materials, given their thermal and chemical stability and their relatively earth-abundant constituent elements. First principal calculations on this compound suggest semiconducting behavior of TiFe 2 Sn, and a relatively flat conduction band that could be associated with a high Seebeck coefficient upon electron doping. TiFe 2 Sn as a thermoelectric material has been studied via synchrotron Xray and neutron diffraction studies that characterize site order/disorder phenomena. Samples fabricated by a three step processing approach were subjected to high temperature Seebeck and electrical resistivity measurements. Ti:Fe anti-site disorder is present in the stoichiometric compound and these defects are reduced in Ti-rich compositions. Additionally, we investigate control of the Seebeck coefficient through the introduction of carriers through the substitution of Sb on the Sn site in these intrinsically p-type materials. Thermoelectric performance in Heusler TiFe

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Nanoscale structural heterogeneity in Ni-rich half-Heusler TiNiSn

Cited by 46 publications

References 27 publications

Lattice thermal conductivity ofTixZryHf1−x−yNiSnhalf-Heusler alloys calculated from first principles: Key role of nature of phonon modes

Lattice thermal conductivity ofTixZryHf1−x−yNiSnhalf-Heusler alloys calculated from first principles: Key role of nature of phonon modes

The Role of Structural and Compositional Heterogeneities in the Insulator-to-Metal Transition in Hole-Doped APd₃O₄ (A = Ca, Sr)

Thermoelectric performance and the role of anti-site disorder in the 24-electron Heusler TiFe₂Sn

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Nanoscale structural heterogeneity in Ni-rich half-Heusler TiNiSn

Cited by 46 publications

References 27 publications

Lattice thermal conductivity ofTixZryHf1−x−yNiSnhalf-Heusler alloys calculated from first principles: Key role of nature of phonon modes

Lattice thermal conductivity ofTixZryHf1−x−yNiSnhalf-Heusler alloys calculated from first principles: Key role of nature of phonon modes

The Role of Structural and Compositional Heterogeneities in the Insulator-to-Metal Transition in Hole-Doped APd3O4 (A = Ca, Sr)

Thermoelectric performance and the role of anti-site disorder in the 24-electron Heusler TiFe2Sn

Contact Info

Product

Resources

About

The Role of Structural and Compositional Heterogeneities in the Insulator-to-Metal Transition in Hole-Doped APd₃O₄ (A = Ca, Sr)

Thermoelectric performance and the role of anti-site disorder in the 24-electron Heusler TiFe₂Sn