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Metals
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Heusler Compounds
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Heusler Compounds

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (31 January 2019) | Viewed by 20542

Special Issue Editor

Prof. Philippe Jund

E-Mail Website
Guest Editor
Institute Charles Gerhardt Montpellier, Montpellier, France
Interests: modeling of materials; classical and ab initio molecular dynamics; relationship structure–physical properties (electronic, vibrational, mechanical); application to: Thermoelectric materials, chalcogenide glasses, oxide glasses, carbon nanotubes, ferrofluids, intermetallic alloys, and Heusler compounds

Special Issue Information

Dear Colleagues,

During the last few years, a great number of researches have been done in the so-called Heusler and half-Heusler compounds. These compounds are archetypical for so-called multifunctional materials since they have interesting magnetic, mechanical and, more recently, thermoelectric properties. The aim of this Special Issue is to present the latest developments in the search of new and promising Heusler of half-Heusler compounds especially (but not exclusively) in the field of thermoelectrics. Both theoretical and experimental contributions will be considered, as well as studies tackling the difficult question of the structure and stability of these materials.

Prof. Philippe Jund
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Heusler
  • Half-Heusler
  • Structure
  • Electronic properties
  • Magnetic properties
  • Thermal properties
  • Defects
  • Phase diagram

Published Papers (5 papers)

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Research

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10 pages, 7083 KiB  
Article
Substitution Versus Full-Heusler Segregation in TiCoSb
by Maryana Asaad, Jim Buckman and Jan-Willem G. Bos
Metals 2018, 8(11), 935; https://doi.org/10.3390/met8110935 - 12 Nov 2018
Cited by 4 | Viewed by 3493
Abstract
Half-Heuslers (HHs) are promising thermoelectric materials with great compositional flexibility. Here, we extend work on the p-type doping of TiCoSb using abundant elements. Ti0.7V0.3Co0.85Fe0.15Sb0.7Sn0.3 samples with nominal 17.85 p-type electron count were [...] Read more.
Half-Heuslers (HHs) are promising thermoelectric materials with great compositional flexibility. Here, we extend work on the p-type doping of TiCoSb using abundant elements. Ti0.7V0.3Co0.85Fe0.15Sb0.7Sn0.3 samples with nominal 17.85 p-type electron count were investigated. Samples prepared using powder metallurgy have negative Seebeck values, S ≤ −120 µV K−1, while arc-melted compositions are compensated semiconductors with S = −45 to +30 µV K−1. The difference in thermoelectric response is caused by variations in the degree of segregation of V(Co0.6Fe0.4)2Sn full-Heusler and Sn phases, which selectively absorb V, Fe, and Sn. The segregated microstructure leads to reduced lattice thermal conductivities, κlat = 4.5−7 W m−1 K−1 near room temperature. The largest power factor, S2/ρ = 0.4 mW m−1 K−2 and ZT = 0.06, is observed for the n-type samples at 800 K. This works extends knowledge regarding suitable p-type dopants for TiCoSb. Full article
(This article belongs to the Special Issue Heusler Compounds)
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21 pages, 4342 KiB  
Article
Synthesis of Pure NiTiSn by Mechanical Alloying: An Investigation of the Optimal Experimental Conditions Supported by First Principles Calculations
by Monique Tillard, Alexandre Berche and Philippe Jund
Metals 2018, 8(10), 835; https://doi.org/10.3390/met8100835 - 17 Oct 2018
Cited by 10 | Viewed by 3394
Abstract
Synthesis of NiTiSn by a mechanical alloying process followed by a high temperature thermal annealing was studied. Experiments were conducted varying parameters like the provided energy, the mechanical alloying reaction time, as well as the annealing temperature and duration. Based on the careful [...] Read more.
Synthesis of NiTiSn by a mechanical alloying process followed by a high temperature thermal annealing was studied. Experiments were conducted varying parameters like the provided energy, the mechanical alloying reaction time, as well as the annealing temperature and duration. Based on the careful investigation of the phases present in the samples by systematic X-ray diffraction (after mechanical alloying and after annealing) and selected microscopy analyses, a reaction mechanism is proposed supported by theoretical calculations at the DFT (Density Functional Theory) level. An energy window to prepare directly NiTiSn has been evidenced. Highly pure NiTiSn has also been obtained by conversion from a multicomponent precursor obtained by low energy mechanical alloying. Full article
(This article belongs to the Special Issue Heusler Compounds)
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7 pages, 4475 KiB  
Article
Synthesis and Thermoelectric Properties of Ni-Doped ZrCoSb Half-Heusler Compounds
by Degang Zhao, Lin Wang, Lin Bo and Di Wu
Metals 2018, 8(1), 61; https://doi.org/10.3390/met8010061 - 17 Jan 2018
Cited by 31 | Viewed by 5385
Abstract
The Ni-doped ZrCo1−xNixSb half-Heusler compounds were prepared by arc-melting and spark plasma sintering technology. X-ray diffraction analysis results showed that all samples were crystallized in a half-Heusler phase. Thermoelectric properties of ZrCo1−xNixSb compounds [...] Read more.
The Ni-doped ZrCo1−xNixSb half-Heusler compounds were prepared by arc-melting and spark plasma sintering technology. X-ray diffraction analysis results showed that all samples were crystallized in a half-Heusler phase. Thermoelectric properties of ZrCo1−xNixSb compounds were measured from room temperature to 850 K. The electrical conductivity and the absolute value of Seebeck coefficient increased with the Ni-doping content increasing due to the Ni substitution at Co. sites. The lattice thermal conductivity of ZrCo1−xNixSb samples was depressed dramatically because of the acoustic phonon scattering and point defect scattering. The figure of merit of ZrCo1−xNixSb compounds was improved due to the decreased thermal conductivity and improved power factor. The maximum ZT value of 0.24 was achieved for ZrCo0.92Ni0.08Sb sample at 850 K. Full article
(This article belongs to the Special Issue Heusler Compounds)
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Review

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10 pages, 2100 KiB  
Review
Recent Advances in Thermoelectric Performance of Half-Heusler Compounds
by S. Joseph Poon
Metals 2018, 8(12), 989; https://doi.org/10.3390/met8120989 - 24 Nov 2018
Cited by 69 | Viewed by 4043
Abstract
Half-Heusler phases (space group F 4 ¯ 3 m , C1b) have recently captured much attention as promising thermoelectric materials for heat-to-electric power conversion in the mid-to-high temperature range. The most studied ones are the RNiSn-type half-Heusler compounds, where R represents [...] Read more.
Half-Heusler phases (space group F 4 ¯ 3 m , C1b) have recently captured much attention as promising thermoelectric materials for heat-to-electric power conversion in the mid-to-high temperature range. The most studied ones are the RNiSn-type half-Heusler compounds, where R represents refractory metals Hf, Zr, and Ti. These compounds have shown a high-power factor and high-power density, as well as good material stability and scalability. Due to their high thermal conductivity, however, the dimensionless figure of merit (zT) of these materials has stagnated near 1 for a long time. Since 2013, the verifiable zT of half-Heusler compounds has risen from 1 to near 1.5 for both n- and p-type compounds in the temperature range of 500–900 °C. In this brief review, we summarize recent advances as well as approaches in achieving the high zT reported. In particular, we discuss the less-exploited strain-relief effect and dopant resonant state effect studied by the author and his collaborators in more detail. Finally, we point out directions for further development. Full article
(This article belongs to the Special Issue Heusler Compounds)
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7 pages, 1471 KiB  
Review
Review of the Thermoelectric Properties in Nanostructured Fe2VAl
by Eric Alleno
Metals 2018, 8(11), 864; https://doi.org/10.3390/met8110864 - 24 Oct 2018
Cited by 28 | Viewed by 3693
Abstract
Besides alloying, nanostructuring was implemented to improve the thermoelectric properties in Fe2VAl. This Heusler alloy indeed displays a thermoelectric figure of merit too small for applications (ZT ~ 0.1 at 300 K) which is caused by a large lattice thermal [...] Read more.
Besides alloying, nanostructuring was implemented to improve the thermoelectric properties in Fe2VAl. This Heusler alloy indeed displays a thermoelectric figure of merit too small for applications (ZT ~ 0.1 at 300 K) which is caused by a large lattice thermal conductivity (λL = 27 W·m−1·K−1 at 300 K). The effect of nanostructuring on the microstructure and on the thermoelectric properties of alloyed Fe2VAl are therefore reviewed. By mechanical alloying followed by spark plasma sintering, the average grain size (D) was decreased to D ~ 300–400 nm in Fe2VAl0.9Si0.1, Fe2VAl0.9Si0.07Sb0.03, Fe2V1.05Al0.95, and Fe2V0.9W0.1Al. As expected, phonon scattering at the numerous grain boundaries lead to a strong decrease in the lattice thermal conductivity, which reached values as small as λL = 3.3 W·m−1·K−1. However, in all the reviewed examples, the thermoelectric figure of merit (ZT) is only marginally or not even improved when comparing to non-nanostructured samples because the electrical resistivity also increases upon nanostructuring. A significantly improved ZT = 0.3 at 500 K was only recently observed in severely deformed Fe2VAl0.95Ta0.05 by high pressure torsion because the very fine microstructure (D ~ 100 nm) strongly enhanced the thermal conductivity reduction. Full article
(This article belongs to the Special Issue Heusler Compounds)
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