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Nanomaterials
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Thermoelectric Properties of Nanomaterials
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Thermoelectric Properties of Nanomaterials

A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Nanoelectronics, Nanosensors and Devices".

Deadline for manuscript submissions: closed (25 October 2021) | Viewed by 11166

Special Issue Editor

Prof. Dr. Oana Cojocaru-Mirédin

E-Mail Website
Guest Editor
Albert-Ludwigs-University of Freiburg, INATECH, 79100 Freiburg, Germany
Interests: nanocharacterization; correlative microscopy; energy materials; solar cells; batteries; thermoelectrics

Special Issue Information

Dear colleagues,

In the last few years, many research groups worldwide have experienced difficulty in increasing the figure-of-merit of thermoelectric materials. This is because most of these thermoelectric materials exhibit a rather complex microstructure, with a hierarchical structure containing point (vacancies and donor defects) and extended defects (dislocations and stacking faults), secondary stable and/or metastable phases, twin boundaries and/or high-angle grain boundaries, and different atomic bonding natures. Therefore, to further increase the performance of thermoelectrics, a detailed and accurate understanding of structural, chemical, electronic, and phonon transport properties from mesoscale down to atomic level is necessary. More specifically, the impact of nanostructuring in thermoelectric properties is vital.

Hence, this Special Issue of Nanomaterials will attempt to cover the most recent advances in nanostructuring for thermoelectric applications, with a special attention to synthesis and characterization. Last but not least, a particular attention will be given to the structural and functional properties of these nanomaterials. Design rules of better thermoelectrics for the future are greatly welcome too. 

Dr. Oana Cojocaru-Mirédin
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. Nanomaterials is an international peer-reviewed open access semimonthly 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 2900 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

  • interfaces
  • nanostructuring
  • bonding
  • nanocharacterization
  • atom probe tomography

Published Papers (4 papers)

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Research

8 pages, 2648 KiB  
Article
Effect of Co-Doping on Thermoelectric Properties of n-Type Bi2Te3 Nanostructures Fabricated Using a Low-Temperature Sol-Gel Method
by Syed Irfan, Muhammad Aizaz Ud Din, Muhammad Qaisar Manzoor and Deliang Chen
Nanomaterials 2021, 11(10), 2719; https://doi.org/10.3390/nano11102719 - 15 Oct 2021
Cited by 5 | Viewed by 1881
Abstract
In this work, a novel low-temperature double solvent sol-gel method was used to fabricate (Sm, Ce, Gd) and (Sn, Se, I) co-doped at Bi and Te-sites, respectively, for Bi2Te3 nanostructures. The phase-purity and high crystallinity of as-synthesized nanostructures were confirmed [...] Read more.
In this work, a novel low-temperature double solvent sol-gel method was used to fabricate (Sm, Ce, Gd) and (Sn, Se, I) co-doped at Bi and Te-sites, respectively, for Bi2Te3 nanostructures. The phase-purity and high crystallinity of as-synthesized nanostructures were confirmed using X-ray diffraction and high-resolution transmission electron microscopy. The nanopowders were hot-pressed by spark plasma sintering into bulk pellets for thermoelectric properties. The spark plasma sintering temperature significantly affects the Seebeck coefficient and electrical conductivity of bulk Bi2Te3 pellets. The electrical conductivities of co-doped samples decrease with an increase in the temperature, but conversely, the Seebeck coefficient is linearly increasing. The power factor showed that the co-dopants enhanced the thermoelectric properties of Bi2Te3 nanopowders. Full article
(This article belongs to the Special Issue Thermoelectric Properties of Nanomaterials)
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19 pages, 1891 KiB  
Article
Enhanced Thermoelectric Performance of Polycrystalline Si0.8Ge0.2 Alloys through the Addition of Nanoscale Porosity
by S. Aria Hosseini, Giuseppe Romano and P. Alex Greaney
Nanomaterials 2021, 11(10), 2591; https://doi.org/10.3390/nano11102591 - 01 Oct 2021
Cited by 7 | Viewed by 1387
Abstract
Engineering materials to include nanoscale porosity or other nanoscale structures has become a well-established strategy for enhancing the thermoelectric performance of dielectrics. However, the approach is only considered beneficial for materials where the intrinsic phonon mean-free path is much longer than that of [...] Read more.
Engineering materials to include nanoscale porosity or other nanoscale structures has become a well-established strategy for enhancing the thermoelectric performance of dielectrics. However, the approach is only considered beneficial for materials where the intrinsic phonon mean-free path is much longer than that of the charge carriers. As such, the approach would not be expected to provide significant performance gains in polycrystalline semiconducting alloys, such as SixGe1-x, where mass disorder and grains provide strong phonon scattering. In this manuscript, we demonstrate that the addition of nanoscale porosity to even ultrafine-grained Si0.8Ge0.2 may be worthwhile. The semiclassical Boltzmann transport equation was used to model electrical and phonon transport in polycrystalline Si0.8Ge0.2 containing prismatic pores perpendicular to the transport current. The models are free of tuning parameters and were validated against experimental data. The models reveal that a combination of pores and grain boundaries suppresses phonon conductivity to a magnitude comparable with the electronic thermal conductivity. In this regime, ZT can be further enhanced by reducing carrier concentration to the electrical and electronic thermal conductivity and simultaneously increasing thermopower. Although increases in ZT are modest, the optimal carrier concentration is significantly lowered, meaning semiconductors need not be so strongly supersaturated with dopants. Full article
(This article belongs to the Special Issue Thermoelectric Properties of Nanomaterials)
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19 pages, 4467 KiB  
Article
Minute-Made, High-Efficiency Nanostructured Bi2Te3 via High-Throughput Green Solution Chemical Synthesis
by Bejan Hamawandi, Hazal Batili, Moon Paul, Sedat Ballikaya, Nuzhet I. Kilic, Rafal Szukiewicz, Maciej Kuchowicz, Mats Johnsson and Muhammet S. Toprak
Nanomaterials 2021, 11(8), 2053; https://doi.org/10.3390/nano11082053 - 12 Aug 2021
Cited by 20 | Viewed by 3954
Abstract
Scalable synthetic strategies for high-quality and reproducible thermoelectric (TE) materials is an essential step for advancing the TE technology. We present here very rapid and effective methods for the synthesis of nanostructured bismuth telluride materials with promising TE performance. The methodology is based [...] Read more.
Scalable synthetic strategies for high-quality and reproducible thermoelectric (TE) materials is an essential step for advancing the TE technology. We present here very rapid and effective methods for the synthesis of nanostructured bismuth telluride materials with promising TE performance. The methodology is based on an effective volume heating using microwaves, leading to highly crystalline nanostructured powders, in a reaction duration of two minutes. As the solvents, we demonstrate that water with a high dielectric constant is as good a solvent as ethylene glycol (EG) for the synthetic process, providing a greener reaction media. Crystal structure, crystallinity, morphology, microstructure and surface chemistry of these materials were evaluated using XRD, SEM/TEM, XPS and zeta potential characterization techniques. Nanostructured particles with hexagonal platelet morphology were observed in both systems. Surfaces show various degrees of oxidation, and signatures of the precursors used. Thermoelectric transport properties were evaluated using electrical conductivity, Seebeck coefficient and thermal conductivity measurements to estimate the TE figure-of-merit, ZT. Low thermal conductivity values were obtained, mainly due to the increased density of boundaries via materials nanostructuring. The estimated ZT values of 0.8–0.9 was reached in the 300–375 K temperature range for the hydrothermally synthesized sample, while 0.9–1 was reached in the 425–525 K temperature range for the polyol (EG) sample. Considering the energy and time efficiency of the synthetic processes developed in this work, these are rather promising ZT values paving the way for a wider impact of these strategic materials with a minimum environmental impact. Full article
(This article belongs to the Special Issue Thermoelectric Properties of Nanomaterials)
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14 pages, 1925 KiB  
Article
Synthesis and Morphological Control of VO2 Nanostructures via a One-Step Hydrothermal Method
by Ozlem Karahan, Ali Tufani, Serkan Unal, I. Burc Misirlioglu, Yusuf Z. Menceloglu and Kursat Sendur
Nanomaterials 2021, 11(3), 752; https://doi.org/10.3390/nano11030752 - 17 Mar 2021
Cited by 21 | Viewed by 3155
Abstract
The morphology of nanostructures is a vital parameter to consider in components comprised of materials exhibiting specific functionalities. The number of process steps and the need for high temperatures can often be a limiting factor when targeting a specific morphology. Here, we demonstrate [...] Read more.
The morphology of nanostructures is a vital parameter to consider in components comprised of materials exhibiting specific functionalities. The number of process steps and the need for high temperatures can often be a limiting factor when targeting a specific morphology. Here, we demonstrate a repeatable synthesis of different morphologies of a highly crystalline monoclinic phase of vanadium dioxide (VO2(M)) using a one-step hydrothermal method. By adjusting the synthesis parameters, such as pH, temperature, and reducing agent concentration in the precursor, VO2 nanostructures with high uniformity and crystallinity are achieved. Some of these morphologies were obtained via the choice of the reducing agent that allowed us to skip the annealing step. Our results indicate that the morphologies of the nanostructures are very sensitive to the hydrazine hydrate (N2H4.H2O) concentration. Another reducing agent, dodecylamine, was used to achieve well-organized and high-quality VO2(M) nanotubes. Differential scanning calorimetry (DSC) experiments revealed that all samples display the monoclinic-to-tetragonal structural transition (MTST) regardless of the morphology, albeit at different temperatures that can be interpreted as the variations in overheating and undercooling limits. VO2(M) structures with a higher surface to volume ratio exhibit a higher overheating limit than those with low ratios. Full article
(This article belongs to the Special Issue Thermoelectric Properties of Nanomaterials)
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