Low thermal conductivity and triaxial phononic anisotropy of SnSe

Carrete, Jesús; Mingo, Natalio; Curtarolo, Stefano

doi:10.1063/1.4895770

Cited by 238 publications

(227 citation statements)

References 27 publications

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“…There are numerous studies on the origin of this impressive property. [98,104,106,107] As shown in Figure 5a, the thermal con ductivity of SnSe is sensitive to the stoichiometry and oxida tion. After the record high ZT of SnSe was reported, it became controversial as to whether these samples are intrinsic.…”

Section: Snsementioning

confidence: 99%

Promising Thermoelectric Bulk Materials with 2D Structures

2017

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Given that more than two thirds of all energy is lost, mostly as waste heat, in utilization processes worldwide, thermoelectric materials, which can directly convert waste heat to electricity, provide an alternative option for optimizing energy utilization processes. After the prediction that superlattices may show high thermoelectric performance, various methods based on quantum effects and superlattice theory have been adopted to analyze bulk materials, leading to the rapid development of thermoelectric materials. Bulk materials with two‐dimensional (2D) structures show outstanding properties, and their high performance originates from both their low thermal conductivity and high Seebeck coefficient due to their strong anisotropic features. Here, the advantages of superlattices for enhancing the thermoelectric performance, the transport mechanism in bulk materials with 2D structures, and optimization methods are discussed. The phenomenological transport mechanism in these materials indicates that thermal conductivities are reduced in 2D materials with intrinsically short mean free paths. Recent progress in the transport mechanisms of Bi2Te3‐, SnSe‐, and BiCuSeO‐based systems is summarized. Finally, possible research directions to enhance the thermoelectric performance of bulk materials with 2D structures are briefly considered.

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Section: Snsementioning

confidence: 99%

Promising Thermoelectric Bulk Materials with 2D Structures

2017

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“…104 The ab initio calculations reveal that the strong PPI of SnSe originates from the large phonon scattering channel and the very anharmonic resonant bonds. 103,105 Recent molecular dynamics calculations of PPI even account for the evolution of κ L with temperature. The stiffening of the transverse optic phonon at Γ point in PbTe with increasing temperature is revealed by both inelastic neutron scattering and AIMD calculations.…”

Section: From the Conventional Phonon-phonon Interactions To Nanostrumentioning

confidence: 99%

“…The phonon mean-free paths, if we define the mean values corresponding to 50 % κ L reduction, 111 vary by 2-3 orders of magnitude according to ab initio IFC calculations. 94,102,[105][106][107][108] Usually, low κ L materials have low MFPs, sometimes even lower than the effective length of charge carriers. This makes the nanostructuring approach less effective for low κ L materials, as verified by the theoretical work with nanoparticles embedded in (Bi, Sb) 2 Te 3 .…”

Section: From the Conventional Phonon-phonon Interactions To Nanostrumentioning

confidence: 99%

On the tuning of electrical and thermal transport in thermoelectrics: an integrated theory–experiment perspective

et al. 2016

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During the last two decades, we have witnessed great progress in research on thermoelectrics. There are two primary focuses. One is the fundamental understanding of electrical and thermal transport, enabled by the interplay of theory and experiment; the other is the substantial enhancement of the performance of various thermoelectric materials, through synergistic optimisation of those intercorrelated transport parameters. Here we review some of the successful strategies for tuning electrical and thermal transport. For electrical transport, we start from the classical but still very active strategy of tuning band degeneracy (or band convergence), then discuss the engineering of carrier scattering, and finally address the concept of conduction channels and conductive networks that emerge in complex thermoelectric materials. For thermal transport, we summarise the approaches for studying thermal transport based on phonon-phonon interactions valid for conventional solids, as well as some quantitative efforts for nanostructures. We also discuss the thermal transport in complex materials with chemical-bond hierarchy, in which a portion of the atoms (or subunits) are weakly bonded to the rest of the structure, leading to an intrinsic manifestation of part-crystalline part-liquid state at elevated temperatures. In this review, we provide a summary of achievements made in recent studies of thermoelectric transport properties, and demonstrate how they have led to improvements in thermoelectric performance by the integration of modern theory and experiment, and point out some challenges and possible directions. INTRODUCTION Thermoelectric (TE) materials are materials that can generate useful electric potentials when subjected to a temperature gradient (known as the Seebeck effect). Conversely, they also transfer heat against the temperature gradient when a current is driven against this potential (known as the Peltier effect). They are promising energy materials with many applications, such as waste heat harvesting, radioisotope TE power generation, and solid state Peltier refrigeration, all of which are driving growing research interest. A key challenge is to improve the TE properties in order to obtain more efficient energy conversion and in turn enable new practical applications. Good TE materials must have excellent electrical transport properties, measured by the TE power factor ( = S 2 σ, where S is the Seebeck coefficient and σ is the electrical conductivity), and also a very low thermal conductivity κ (composed of the electronic contribution κ e , the lattice contribution κ L , and the bipolar contribution κ bi ). Combining the two aspects gives us the dimensionless figure of merit ZT,

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“…SnSe received recent attention for its thermoelectric properties [15]. Given its triaxial phononic anisotropy [16], it additionally provides a challenging benchmark test for the thin film conduction model we present below. * bjorn.vermeersch@cea.fr…”

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confidence: 99%

Cross-plane heat conduction in thin films with ab-initio phonon dispersions and scattering rates

Vermeersch

Carrete

Mingo

2016

Applied Physics Letters

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We present a first-principles study of the cross-plane thermal conductivity κ ⊥ in a wide variety of semiconductor thin films. We introduce a simple suppression model that matches variance-reduced Monte Carlo simulations with ab-initio phonon dispersions and scattering rates within ≤ 5% even for anisotropic compounds. This, in turn, enables accurate κ ⊥ reconstruction from tabulated cumulative conductivity curves κΣ(Λ ⊥ ). We furthermore reveal, and explain, a distinct quasiballistic regime characterised by a fractional thickness dependence κ ⊥ ∼ L 2−α in alloys (where α is the Lévy exponent) and logarithmic dependence κ ⊥ ∼ ln(L) in single crystals. These observations culminate in the formulation of two compact parametric forms for κ ⊥ (L) that can fit the first-principles curves across the entire ballistic-diffusive range within a few percent for all investigated compounds.Phonon-mediated heat conduction in thin films plays an important role in nanoscale devices [1, 2] and received increasing theoretical attention [3][4][5][6][7][8][9][10]. Interestingly, cross-plane thermal transport has posed a considerably harder challenge than its in-plane counterpart. An exact solution of the Boltzmann transport equation (BTE) in cross-plane geometries has been obtained only very recently [7] and provides the film conductivity at thickness L as an integral over phonon frequencyHere S is a 'suppression function' that contains the thin film physics and κ(ω) denotes the bulk spectral conductivity. Evaluation of the latter often relies on analytical models with isotropic dispersions [8-10] for mathematical convenience. More realistic phonon spectra can also be utilised through frequency binning, but this procedure becomes problematic in anisotropic compounds. In this work, we adopt a first-principles framework [11,12] that goes well beyond the predictive power of spectral formulations. We subsequently show that the resulting cross-plane thin film conductivity curves κ(L) can be captured by compact models that effortlessly maintain their accuracy in anisotropic compounds. In the process, we also reveal quasiballistic regimes in both alloys and single crystals with distinct film thickness dependences.We performed our ab-initio study for a variety of semiconductors selected for their technological relevance. Thin Si films play a key role in silicon-on-insulator de- We calculated ab-initio heat capacities C( k), group velocities v( k) and scattering rates τ −1 ( k) using the procedure described in Ref. 17. The adopted method has been tested on a variety of bulk compounds and provides results in good agreement with experiments [11]. Phonon properties are resolved over a uniform wavevector grid with N 3 k points, where we have set N k to 24 for diamond/zincblende crystals, 16 for wurtzites and 12 for Pnma SnSe. Scattering rates τ −1 = τ −1 anh + τ −1 har and mean free paths (MFPs) Λ = v τ account for anharmonic (three-phonon) and harmonic (isotope/alloy) scattering mechanisms. Alloys were treated under the virtual crystal approxim...

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Low thermal conductivity and triaxial phononic anisotropy of SnSe

Cited by 238 publications

References 27 publications

Promising Thermoelectric Bulk Materials with 2D Structures

Promising Thermoelectric Bulk Materials with 2D Structures

On the tuning of electrical and thermal transport in thermoelectrics: an integrated theory–experiment perspective

Cross-plane heat conduction in thin films with ab-initio phonon dispersions and scattering rates

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