scholarly journals α-Bi2Sn2O7: a potential room temperature n-type oxide thermoelectric

2020 ◽  
Vol 8 (32) ◽  
pp. 16405-16420 ◽  
Author(s):  
Warda Rahim ◽  
Jonathan M. Skelton ◽  
David O. Scanlon
Keyword(s):  
Thermal Conductivity ◽  
Low Temperature ◽  
Ab Initio ◽  
Room Temperature ◽  
Lattice Thermal Conductivity ◽  
Phonon Scattering ◽  
High Density ◽  
Earth Abundant ◽  
Scattering Events

Using ab initio methods, we predict α-Bi2Sn2O7 to have an ultra-low lattice thermal conductivity at room temperature due to the high density of phonon scattering events, which makes it a potential earth-abundant n-type low temperature thermoelectric.

scholarly journals α-Bi2Sn2O7: A Potential Room Temperature n-type Oxide Thermoelectric

2020 ◽  
Author(s):  
Warda Rahim ◽  
Jonathan Skelton ◽  
David Scanlon
Keyword(s):  
Thermal Conductivity ◽  
Low Temperature ◽  
Room Temperature ◽  
Lattice Thermal Conductivity ◽  
Phonon Transport ◽  
Consumer Electronics ◽  
Low Grade ◽  
Oxide Material ◽  
Thermoelectric Efficiency ◽  
Oxide Thermoelectrics

<p>Interest in oxide thermoelectrics has been building due to their high thermal stability and earth-abundant constituent elements. However, the thermoelectric efficiency of flagship oxide materials remains comparatively low, and most materials only reach the maximum figure of merit, <i>ZT</i>, at very high temperatures, above those where the majority of low-grade industrial heat is emitted. It is important to identify thermoelectrics with high conversion efficiency closer to room temperature, particularly for lower-temperature applications such as in domestic heating, consumer electronics and electric vehicles. One of the main factors limiting the efficiency of oxide thermoelectrics is their large lattice thermal conductivities, which has inspired research into more structurally complex materials. In this study, we apply first-principles modelling to assess the low-temperature polymorph of Bi<sub>2</sub>Sn<sub>2</sub>O<sub>7</sub> (α-Bi<sub>2</sub>Sn<sub>2</sub>O<sub>7</sub>) as a potential thermoelectric material, due to its complex crystal structure, which should suppress phonon transport, and the presence of Bi <i>p</i> and Sn <i>s</i> states in the conduction band, which should yield high electrical conductivity when donor (<i>n</i>) doped. Lattice-dynamics calculations using third-order perturbation theory predict an ultralow room-temperature lattice thermal conductivity of 0.4 W m<sup>-1</sup> K<sup>-1</sup>, the lowest ever predicted for an oxide material, and suggest that nanostructuring to a grain size of 5 nm could further decrease this to 0.28 W m<sup>-1</sup> K<sup>-1</sup>. The ultralow lattice thermal conductivity gives α-Bi<sub>2</sub>Sn<sub>2</sub>O<sub>7 </sub>a maximum <i>ZT</i> of 0.36 at 385 K (0.46 with nanostructuring), which is the highest low-temperature value predicted for an oxide thermoelectric. Most importantly, our analysis highlights the relationship between the structural complexity, the chemical nature of the cation, and the short phonon lifetimes, and thus provides guidelines for identifying other novel high-performance oxide thermoelectrics.</p>

scholarly journals Excellent Room-Temperature Thermoelectricity of 2D GeP3: Mexican-Hat-Shaped Band Dispersion and Ultralow Lattice Thermal Conductivity

Molecules ◽  
2021 ◽  
Vol 26 (21) ◽  
pp. 6376
Author(s):  
Cong Wang ◽  
Zhiyuan Xu ◽  
Ke Xu ◽  
Guoying Gao
Keyword(s):  
Thermal Conductivity ◽  
Power Factor ◽  
Room Temperature ◽  
Lattice Thermal Conductivity ◽  
Transport Theory ◽  
Phonon Scattering ◽  
Quantum Confinement Effect ◽  
Boltzmann Transport Theory ◽  
Mexican Hat ◽  
P Type

Although some atomically thin 2D semiconductors have been found to possess good thermoelectric performance due to the quantum confinement effect, most of their behaviors occur at a higher temperature. Searching for promising thermoelectric materials at room temperature is meaningful and challenging. Inspired by the finding of moderate band gap and high carrier mobility in monolayer GeP3, we investigated the thermoelectric properties by using semi-classical Boltzmann transport theory and first-principles calculations. The results show that the room-temperature lattice thermal conductivity of monolayer GeP3 is only 0.43 Wm−1K−1 because of the low group velocity and the strong anharmonic phonon scattering resulting from the disordered phonon vibrations with out-of-plane and in-plane directions. Simultaneously, the Mexican-hat-shaped dispersion and the orbital degeneracy of the valence bands result in a large p-type power factor. Combining this superior power factor with the ultralow lattice thermal conductivity, a high p-type thermoelectric figure of merit of 3.33 is achieved with a moderate carrier concentration at 300 K. The present work highlights the potential applications of 2D GeP3 as an excellent room-temperature thermoelectric material.

scholarly journals α-Bi2Sn2O7: A Potential Room Temperature n-type Oxide Thermoelectric

2020 ◽  
Author(s):  
Warda Rahim ◽  
Jonathan Skelton ◽  
David Scanlon
Keyword(s):  
Thermal Conductivity ◽  
Low Temperature ◽  
Room Temperature ◽  
Lattice Thermal Conductivity ◽  
Phonon Transport ◽  
Consumer Electronics ◽  
Low Grade ◽  
Oxide Material ◽  
Thermoelectric Efficiency ◽  
Oxide Thermoelectrics

<p>Interest in oxide thermoelectrics has been building due to their high thermal stability and earth-abundant constituent elements. However, the thermoelectric efficiency of flagship oxide materials remains comparatively low, and most materials only reach the maximum figure of merit, <i>ZT</i>, at very high temperatures, above those where the majority of low-grade industrial heat is emitted. It is important to identify thermoelectrics with high conversion efficiency closer to room temperature, particularly for lower-temperature applications such as in domestic heating, consumer electronics and electric vehicles. One of the main factors limiting the efficiency of oxide thermoelectrics is their large lattice thermal conductivities, which has inspired research into more structurally complex materials. In this study, we apply first-principles modelling to assess the low-temperature polymorph of Bi<sub>2</sub>Sn<sub>2</sub>O<sub>7</sub> (α-Bi<sub>2</sub>Sn<sub>2</sub>O<sub>7</sub>) as a potential thermoelectric material, due to its complex crystal structure, which should suppress phonon transport, and the presence of Bi <i>p</i> and Sn <i>s</i> states in the conduction band, which should yield high electrical conductivity when donor (<i>n</i>) doped. Lattice-dynamics calculations using third-order perturbation theory predict an ultralow room-temperature lattice thermal conductivity of 0.4 W m<sup>-1</sup> K<sup>-1</sup>, the lowest ever predicted for an oxide material, and suggest that nanostructuring to a grain size of 5 nm could further decrease this to 0.28 W m<sup>-1</sup> K<sup>-1</sup>. The ultralow lattice thermal conductivity gives α-Bi<sub>2</sub>Sn<sub>2</sub>O<sub>7 </sub>a maximum <i>ZT</i> of 0.36 at 385 K (0.46 with nanostructuring), which is the highest low-temperature value predicted for an oxide thermoelectric. Most importantly, our analysis highlights the relationship between the structural complexity, the chemical nature of the cation, and the short phonon lifetimes, and thus provides guidelines for identifying other novel high-performance oxide thermoelectrics.</p>

Lattice Thermal Conductivity Modelling of a Diatomic Nanoscale Material

2020 ◽  
Vol 10 (5) ◽  
pp. 602-609
Author(s):  
Adil H. Awad
Keyword(s):  
Thermal Conductivity ◽  
Lattice Thermal Conductivity ◽  
Phonon Scattering ◽  
Correction Term ◽  
Nanoscale Material ◽  
New Approach ◽  
Two Samples ◽  
Conductivity Modelling ◽  
Callaway Model

Introduction: A new approach for expressing the lattice thermal conductivity of diatomic nanoscale materials is developed. Methods: The lattice thermal conductivity of two samples of GaAs nanobeam at 4-100K is calculated on the basis of monatomic dispersion relation. Phonons are scattered by nanobeam boundaries, point defects and other phonons via normal and Umklapp processes. Methods: A comparative study of the results of the present analysis and those obtained using Callaway formula is performed. We clearly demonstrate the importance of the utilised scattering mechanisms in lattice thermal conductivity by addressing the separate role of the phonon scattering relaxation rate. The formulas derived from the correction term are also presented, and their difference from Callaway model is evident. Furthermore their percentage contribution is sufficiently small to be neglected in calculating lattice thermal conductivity. Conclusion: Our model is successfully used to correlate the predicted lattice thermal conductivity with that of the experimental observation.

scholarly journals Local ferroelectric polarization switching driven by nanoscale distortions in thermoelectric $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Aastha Vasdev ◽  
Moinak Dutta ◽  
Shivam Mishra ◽  
Veerpal Kaur ◽  
Harleen Kaur ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Lattice Thermal Conductivity ◽  
Direct Evidence ◽  
Temperature Dependent ◽  
Force Microscopy ◽  
Ferroelectric Domains ◽  
Pdf Analysis ◽  
Ferroelectric Transition Temperature

AbstractA remarkable decrease in the lattice thermal conductivity and enhancement of thermoelectric figure of merit were recently observed in rock-salt cubic SnTe, when doped with germanium (Ge). Primarily, based on theoretical analysis, the decrease in lattice thermal conductivity was attributed to local ferroelectric fluctuations induced softening of the optical phonons which may strongly scatter the heat carrying acoustic phonons. Although the previous structural analysis indicated that the local ferroelectric transition temperature would be near room temperature in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te , a direct evidence of local ferroelectricity remained elusive. Here we report a direct evidence of local nanoscale ferroelectric domains and their switching in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te using piezoeresponse force microscopy(PFM) and switching spectroscopy over a range of temperatures near the room temperature. From temperature dependent (250–300 K) synchrotron X-ray pair distribution function (PDF) analysis, we show the presence of local off-centering distortion of Ge along the rhombohedral direction in global cubic $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te . The length scale of the $${\text {Ge}}^{2+}$$ Ge 2 + off-centering is 0.25–0.10 Å near the room temperatures (250–300 K). This local emphatic behaviour of cation is the cause for the observed local ferroelectric instability, thereby low lattice thermal conductivity in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te .

scholarly journals First-principles predictions of low lattice thermal conductivity and high thermoelectric performance of AZnSb (A = Rb, Cs)

RSC Advances ◽  
2021 ◽  
Vol 11 (25) ◽  
pp. 15486-15496
Author(s):  
Enamul Haque
Keyword(s):  
Thermal Conductivity ◽  
Debye Temperature ◽  
Layered Structure ◽  
First Principles ◽  
Lattice Thermal Conductivity ◽  
Phonon Scattering ◽  
Thermoelectric Performance

The layered structure, and presence of heavier elements Rb/Cs and Sb induce high anharmonicity, low Debye temperature, intense phonon scattering, and hence, low lattice thermal conductivity.

Glass-Oxide Nanocomposites as Effective Thermal Insulation Materials

2013 ◽  
Vol 1558 ◽  
Author(s):  
Qing Hao ◽  
Minqing Li ◽  
Garrett Joseph Coleman ◽  
Qiang Li ◽  
Pierre Lucas
Keyword(s):  
Thermal Conductivity ◽  
Thermal Insulation ◽  
Room Temperature ◽  
Phonon Scattering ◽  
Material Composition ◽  
Insulation Materials ◽  
Atomic Structures ◽  
Porous Nanocomposites ◽  
Theoretical Minimum

ABSTRACTWith extremely disordered atomic structures, a glass possesses a thermal conductivity k that approaches the theoretical minimum of its composition, known as the Einstein’s limit.1 Depending on the material composition and the extent of disorder, the thermal conductivity of some glasses can be down to 0.1-0.3 W/m∙K at room temperature,2,3 representing some of the lowest k values among existing solids. Such a low k can be further reduced by the interfacial phonon scattering within a nanocomposite that can be used for thermal insulation applications. In this work, nanocomposites hot pressed from the mixture of glass nanopowder (GeSe4 or Ge20Te70Se10) and commercial SiO2 nanoparticles, or pure glass nanopowder, are investigated for the potential k reduction. It is found that adding SiO2 nanoparticles will instead increase k if the measured k values for usually porous nanocomposites are converted into those for the corresponding solid (kSolid) with Eucken’s formula. In contrast, pure glass nano-samples always show kSolid data significantly reduced from that for the starting glass. For a pure GeSe4 nano-sample, kSolid would beat the Einstein’s limit for its composition.

Development of Toughened, Fine Grained, Recrystallized W-1.1%TiC

2021 ◽  
Vol 1024 ◽  
pp. 103-109
Author(s):  
Shunsuke Makimura ◽  
Hiroaki Kurishita ◽  
Koichi Niikura ◽  
Hun Chea Jung ◽  
Hiroyuki Ishizaki ◽  
...  
Keyword(s):  
Melting Point ◽  
Low Temperature ◽  
Fracture Strength ◽  
Room Temperature ◽  
Target Material ◽  
High Density ◽  
High Melting ◽  
High Melting Point ◽  
Irradiation Embrittlement ◽  
Fine Grained

Tungsten (W) is a principal candidate as target material because of its high density and extremely high melting point. W inherently has a critical disadvantage of its brittleness at around room temperature (low temperature brittleness), recrystallization embrittlement, and irradiation embrittlement. TFGR (Toughened, Fine Grained, Recrystallized) W-1.1%TiC has been considered as a realized solution to the embrittlement problems. We started to fabricate TFGR W-1.1%TiC in 2016 under collaboration between KEK and Metal Technology Co. LTD (MTC). The TFGR W-1.1%TiC samples were successfully fabricated in June, 2018. As a result, the specimen showed slight bend ductility and 2.6 GPa of fracture strength.

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