The lattice thermal conductivity (κph) of metals and semimetals is limited by phonon‐phonon scattering at high temperatures and by electron‐phonon scattering at low temperatures or in some systems with weak phonon‐phonon scattering. Following the demonstration of a phonon band engineering approach to achieve an unusually high κphin semiconducting cubic‐boron arsenide (c‐BAs), recent theories have predicted ultrahigh κphof the semimetal tantalum nitride in the θ‐phase (θ‐TaN) with hexagonal tungsten carbide (WC) structure due to the combination of a small electron density of states near the Fermi level and a large phonon band gap, which suppress electron‐phonon and three‐phonon scattering, respectively. Here, measurements on the thermal and electrical transport properties of polycrystalline θ‐TaN converted from the ε phase via high‐pressure synthesis are reported. The measured thermal conductivity of the θ‐TaN samples shows weak temperature dependence above 200 K and reaches up to 90 Wm−1K−1, one order of magnitude higher than values reported for polycrystalline ε‐TaN and δ‐TaN thin films. These results agree with theoretical calculations that account for phonon scattering by 100 nm‐level grains and suggest κphincrease above the 249 Wm−1K−1value predicted for single‐crystal WC when the grain size of θ‐TaN is increased above 400 nm.
This article shows experimentally that an external electric field affects the velocity of the longitudinal acoustic phonons (
- Award ID(s):
- 2133718
- PAR ID:
- 10478909
- Publisher / Repository:
- AAAS
- Date Published:
- Journal Name:
- Science Advances
- Volume:
- 9
- Issue:
- 5
- ISSN:
- 2375-2548
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract -
Low-temperature thermal conductivity ( κ ), as well as the magnetic properties and specific heat, are studied for the frustrated zigzag spin-chain material SrEr 2 O 4 by using single-crystal samples. The specific heat data indicate the long-range antiferromagnetic transition at ∼ 0.73 K and the existence of strong magnetic fluctuations. The magnetizations at very low temperatures for magnetic field along the c axis (spin chain direction) or the a axis reveal the field-induced magnetic transitions. The κ shows a strong dependence on magnetic field, applied along the c axis or the a axis, which is closely related to the magnetic transitions. Furthermore, high magnetic field induces a strong increase of κ . These results indicate that thermal conductivity along either the c axis or the a axis are mainly contributed by phonons, while magnetic excitations play a role of scattering phonons.more » « less
-
more » « less
Nanocrystalline silicon can have unique thermal transport and mechanical properties governed by its constituent grain microstructure. Here, we use phonon ray-tracing and molecular dynamics simulations to demonstrate the largely tunable thermomechanical behaviors with varying grain sizes (a0) and aspect ratios (ξ). Our work shows that, by selectively increasing the grain size along the heat transfer direction while keeping the grain area constant, the in-plane lattice thermal conductivity (kx) increases more significantly than the cross-plane lattice thermal conductivity (ky) due to anisotropic phonon–grain boundary scattering. While kx generally increases with increasing ξ, a critical value exists for ξ at which kx reaches its maximum. Beyond this transition point, further increases in ξ result in a decrease in kx due to substantial scattering of low-frequency phonons with anisotropic grain boundaries. Moreover, we observe reductions in the elastic and shear modulus with decreasing grain size, and this lattice softening leads to significant reductions in phonon group velocity and thermal conductivity. By considering both thermal and mechanical size effects, we identify two distinct regimes of thermal transport, in which anisotropic phonon–grain boundary scattering becomes more appreciable at low temperatures and lattice softening becomes more pronounced at high temperatures. Through phonon spectral analysis, we attribute the significant thermal conductivity anisotropy in nanograined silicon to grain boundary scattering of low-frequency phonons and the softening-driven thermal conductivity reduction to Umklapp scattering of high-frequency phonons. These findings offer insights into the manipulation of thermomechanical properties of nanocrystalline silicon via microstructure engineering, carrying profound implications for the development of future nanomaterials.
-
Utilizing first-principles calculations combined with phonon Boltzmann transport theory up to fourth-order anharmonicity, we systematically investigate the thermal transport properties of the biphenylene network [BPN, recently synthesized experimentally by Fan et al. , Science , 2021, 372 , 852–856] and hydrogenated BPN (HBPN). The calculations show that four-phonon scattering significantly affects the lattice thermal conductivity ( κ ) of BPN. At room temperature, the κ of BPN is reduced from 582.32 (1257.07) W m −1 K −1 to 309.56 (539.88) W m −1 K −1 along the x ( y ) direction after considering the four-phonon scattering. Moreover, our results demonstrate that the thermal transport in BPN could also be greatly suppressed by hydrogenation, where the κ of HBPN along the x ( y ) direction is merely 16.62% (10.14%) of that of pristine BPN at 300 K. The mechanism causing such an obvious decrease of κ of HBPN is identified to be due to the enhanced phonon scattering rate and reduced group velocity, which is further revealed by the increased scattering phase space and weakened C–C bond. The results presented in this work shed light on the intrinsic thermal transport features of BPN and HBPN, which will help us to understand the phonon transport processes and pave the way for their future developments in the thermal field.more » « less
-
Abstract Materials with tunable thermal properties enable on-demand control of temperature and heat flow, which is an integral component in the development of solid-state refrigeration, energy scavenging, and thermal circuits. Although gap-based and liquid-based thermal switches that work on the basis of mechanical movements have been an effective approach to control the flow of heat in the devices, their complex mechanisms impose considerable costs in latency, expense, and power consumption. As a consequence, materials that have multiple solid-state phases with distinct thermal properties are appealing for thermal management due to their simplicity, fast switching, and compactness. Thus, an ideal thermal switch should operate near or above room temperature, have a simple trigger mechanism, and offer a quick and large on/off switching ratio. In this study, we experimentally demonstrate that manipulating phonon scattering rates can switch the thermal conductivity of antiferroelectric PbZrO 3 bidirectionally by −10% and +25% upon applying electrical and thermal excitation, respectively. Our approach takes advantage of two separate phase transformations in PbZrO 3 that alter the phonon scattering rate in different manners. In this study, we demonstrate that PbZrO 3 can serve as a fast (<1 second), repeatable, simple trigger, and reliable thermal switch with a net switching ratio of nearly 38% from ~1.20 to ~1.65 W m −1 K −1 .more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1126/sciadv.add7194
