Filters

2020 - 20213

More filters

20223
Reset filters

Settings

Author: Zhu, Taishan × Version: publishedVersion ×

Search Results

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Unveiling the phonon scattering mechanisms in half-Heusler thermoelectric compounds
    (Cambridge : RSC Publ., 2020) He, Ran; Zhu, Taishan; Wang, Yumei; Wolff, Ulrike; Jaud, Jean-Christophe; Sotnikov, Andrei; Potapov, Pavel; Wolf, Daniel; Ying, Pingjun; Wood, Max; Liu, Zhenhui; Feng, Le; Perez Rodriguez, Nicolas; Snyder, G. Jeffrey; Grossman, Jeffrey C.; Nielsch, Kornelius; Schierning, Gabi
    Half-Heusler (HH) compounds are among the most promising thermoelectric (TE) materials for large-scale applications due to their superior properties such as high power factor, excellent mechanical and thermal reliability, and non-toxicity. Their only drawback is the remaining-high lattice thermal conductivity. Various mechanisms were reported with claimed effectiveness to enhance the phonon scattering of HH compounds including grain-boundary scattering, phase separation, and electron–phonon interaction. In this work, however, we show that point-defect scattering has been the dominant mechanism for phonon scattering other than the intrinsic phonon–phonon interaction for ZrCoSb and possibly many other HH compounds. Induced by the charge-compensation effect, the formation of Co/4d Frenkel point defects is responsible for the drastic reduction of lattice thermal conductivity in ZrCoSb1−xSnx. Our work systematically depicts the phonon scattering profile of HH compounds and illuminates subsequent material optimizations.
  • Thumbnail Image
    Item
    Charting lattice thermal conductivity for inorganic crystals and discovering rare earth chalcogenides for thermoelectrics
    (Cambridge : RSC Publ., 2021) Zhu, Taishan; He, Ran; Gong, Sheng; Xie, Tian; Gorai, Prashun; Nielsch, Kornelius; Grossman, Jeffrey C.
    Thermoelectric power generation represents a promising approach to utilize waste heat. The most effective thermoelectric materials exhibit low thermal conductivity κ. However, less than 5% out of about 105 synthesized inorganic materials are documented with their κ values, while for the remaining 95% κ values are missing and challenging to predict. In this work, by combining graph neural networks and random forest approaches, we predict the thermal conductivity of all known inorganic materials in the Inorganic Crystal Structure Database, and chart the structural chemistry of κ into extended van-Arkel triangles. Together with the newly developed κ map and our theoretical tool, we identify rare-earth chalcogenides as promising candidates, of which we measured ZT exceeding 1.0. We note that the κ chart can be further explored, and our computational and analytical tools are applicable generally for materials informatics.
  • Thumbnail Image
    Item
    High-Pressure-Sintering-Induced Microstructural Engineering for an Ultimate Phonon Scattering of Thermoelectric Half-Heusler Compounds
    (Weinheim : Wiley-VCH, 2021) He, Ran; Zhu, Taishan; Ying, Pingjun; Chen, Jie; Giebeler, Lars; Kühn, Uta; Grossman, Jeffrey C.; Wang, Yumei; Nielsch, Kornelius
    Thermal management is of vital importance in various modern technologies such as portable electronics, photovoltaics, and thermoelectric devices. Impeding phonon transport remains one of the most challenging tasks for improving the thermoelectric performance of certain materials such as half-Heusler compounds. Herein, a significant reduction of lattice thermal conductivity (κL) is achieved by applying a pressure of ≈1 GPa to sinter a broad range of half-Heusler compounds. Contrasting with the common sintering pressure of less than 100 MPa, the gigapascal-level pressure enables densification at a lower temperature, thus greatly modifying the structural characteristics for an intensified phonon scattering. A maximum κL reduction of ≈83% is realized for HfCoSb from 14 to 2.5 W m−1 K−1 at 300 K with more than 95% relative density. The realized low κL originates from a remarkable grain-size refinement to below 100 nm together with the abundant in-grain defects, as determined by microscopy investigations. This work uncovers the phonon transport properties of half-Heusler compounds under unconventional microstructures, thus showing the potential of high-pressure compaction in advancing the performance of thermoelectric materials.