Potential Thermoelectric Performance Research Articles

Theoretical Study of Lattice Thermal Conductivity of NbFeM (M = Sb, Bi) for Potential Thermoelectric Performance

Theoretical Study of Lattice Thermal Conductivity of NbFeM (M = Sb, Bi) for Potential Thermoelectric Performance

Theoretical insight into potential thermoelectric performance of ternary metal phosphide CaAgP

Metal phosphides have recently emerged as promising thermoelectric materials with high performance and low cost of constituent elements. In this work, we provide atomistic insight into thermoelectric performance of ternary metal phosphide CaAgP using first-principles calculations of transport properties, focusing on an accurate description of phonon–phonon and electron–phonon interactions. Applying a unified theory for lattice thermal conductivity and momentum, self-energy relaxation time approximation approaches for phonon-limited electronic transports result in overall agreement with experiment for transport properties of CaAgP. Having a promising thermoelectric figure of merit ZT over 0.48 at 650 K, nano-phasing or doping is suggested to further enhance the thermoelectric performance.

Large thermopower in topological surface state of Sn-BSTS topological insulators: Thermoelectrics and energy-dependent relaxation times

Topological surface Dirac states (TSDSs) generated in three-dimensional topological insulators (3D-TIs) are currently of significant interest for new science and advanced technologies. In contrast to many other thermoelectric materials, 3D-TIs exhibit a significant potential to achieve a large enhancement in thermoelectric power factor ($PF=\ensuremath{\sigma}{S}^{2}$) due to their special topological symmetry. However, only limited experiments and discussions have been made so far for elucidating the thermoelectric properties of TSDS. Herein, we report a large $S$ and $\mathit{PF}$ observed for high-quality single-crystal flakes of $\mathrm{Sn}\text{\ensuremath{-}}\mathrm{B}{\mathrm{i}}_{1.1}{\mathrm{Sb}}_{0.9}\mathrm{Te}{\mathrm{S}}_{2}$ (Sn-BSTS). Accurate interpretations that the energy-dependent relaxation times $\ensuremath{\tau}(E)$ play an important role in thermoelectrical transport of 3D-TIs are provided. Among 3D-TIs, Sn-BSTS has the highest bulk insulation and shows intrinsic TSDS transport without bulk contributions, along with its hallmark of quantum integer Hall effect at high temperatures. Based on the longitudinal/transverse electrical transport and the thermoelectric coefficient, $\ensuremath{\tau}(E)\ensuremath{\propto}{E}^{0.21}$ is accurately deduced. As a consequence of the energy-dependent $\ensuremath{\tau}(E)$, a large enhancement in both $S$ and $\mathit{PF}$ is obtained ($S=58\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{V}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ and $PF=5.0\phantom{\rule{0.16em}{0ex}}\mathrm{mW}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}1}\phantom{\rule{0.28em}{0ex}}{\mathrm{K}}^{\ensuremath{-}2}$ at 77 K), leading to a large increase of 160% for $S$ and 280% for $\mathit{PF}$ when compared to those of graphene at 77 K. The potential thermoelectric performance of the pure TSDS is discussed based on the Boltzmann transport equations.

Thermoelectric properties of Cu4Ge3Se5with an intrinsic disordered zinc blende structure

Ternary Cu4Ge3Se5with a disordered zinc blende structure shows a low intrinsic lattice thermal conductivity and potential thermoelectric performance.

Enhanced thermoelectric properties of YbZn2Sb2−xBix through a synergistic effect via Bi-doping

Recently, extensive research has been done to explore the potential thermoelectric performance of p-Type Zintl compounds AB2Sb2 (A = Ca, Yb, Eu, Sr, Mg; B = Zn, Mn, Cd, Mg), mainly focus on A-site substitution and/or B-site substitution effect. Herein, we report that both power factors and thermal conductivities are simultaneously optimized to increase ZT values via substitution of Sb atoms with the isoelectronic Bi atoms in YbZn2Sb2−xBix compounds. We found that the power factor could be enhanced by 27%, as a result of improved electrical conductivities and the maintained Seebeck coefficients. The former is obtained from an increase of carrier density through a shift of Fermi level via Bi doping, which is supported by XPS analysis. The Seebeck coefficients are maintained due to the increased effective mass. Moreover, the lowest lattice thermal conductivity (0.47 Wm−1 K−1 at 723K) is below the lattice thermal conductivity limit due to enhanced phonon scattering via Bi-doping, which is analyzed by the Callaway model. Benefiting from the synergistic effect, the ZT of Bi-doping samples are significantly enhanced compared with that of the pristine one. These results probably offer a synergistic strategy to enhance ZT for p-Type Zintl compounds AB2Sb2 and other high-efficiency thermoelectric materials.

Thermoelectric properties of In-Hg co-doping in SnTe: Energy band engineering

Synergistic effect of band convergence and resonant level could be manipulated in SnTe by co-doping In and Hg, leading to a potential thermoelectric performance enhancement in a much wider temperature range. In this work we carefully investigated thermoelectric properties of the In-Hg co-doped SnTe, synthesized by a hot pressing method. With this co-doping the Seebeck coefficients of the co-doped samples were greatly improved (over 50 μVK−1) at the room temperature. Although power factors of the In-Hg co-doped SnTe were also able to be optimized, the peak ZT (0.9 at 850 K in Sn0.98Bi0.02Te-1%HgInTe2), however, is not high enough when comparing to other co-doped SnTe systems. This may be caused by the relatively high lattice thermal conductivity. An apparent competition between band convergence doping and resonant level doping was observed in our experiment. The results suggest that band engineering via co-doping should be further understood in order to optimize the thermoelectric properties inside the material system.

Potential thermoelectric performance of hole-doped Cu2O

High thermoelectric performance in oxides requires stable conductive materials that have suitable band structures. Here we show, based on an analysis of the thermopower and related properties using first-principles calculations and Boltzmann transport theory in the relaxation time approximation, that hole-doped Cu2O may be such a material. We find that hole-doped Cu2O has a high thermopower of above 200 μV K−1 even with doping levels as high as 5.2 × 1020 cm−3 at 500 K, mainly attributed to the heavy valence bands of Cu2O. This is reminiscent of the cobaltate family of high-performance oxide thermoelectrics and implies that hole-doped Cu2O could be an excellent thermoelectric material if suitably doped.

Electronic and thermoelectric properties of CoSbS and FeSbS

We present a combined theoretical and experimental study of the potential thermoelectric performance of three transition metal antimonide sulfides, CoSbS, FeSbS, and NiSbS. From theory we find that NiSbS is metallic and hence of little interest regarding thermoelectric performance. CoSbS and FeSbS are both semiconductors with rather heavy valence and conduction bands, whose thermopower can exceed 200 $\ensuremath{\mu}$V/K at temperatures of 900 K and carrier concentrations of 10${}^{21}$cm${}^{\ensuremath{-}3}$, which is similar to the $n$-type high performance thermoelectric filled skutterudites. The experimental results on several non-optimized $n$-type CoSbS samples confirm its semiconducting nature and indicate a potential for good high temperature thermoelectric performance, finding a $ZT$ for two of the samples of 0.35 at 773 K. Substantially higher $ZT$ values may be possible if the lattice thermal conductivity can be reduced by alloying and the effects of extrinsic scattering, which appear to be substantial in the experimental results, are reduced.

Apparatus for the high temperature measurement of the Seebeck coefficient in thermoelectric materials

The Seebeck coefficient is a physical parameter routinely measured to identify the potential thermoelectric performance of a material. However, researchers employ a variety of techniques, conditions, and probe arrangements to measure the Seebeck coefficient, resulting in conflicting materials data. To compare and evaluate these methodologies, and to identify optimal Seebeck coefficient measurement protocols, we have developed an improved experimental apparatus to measure the Seebeck coefficient under multiple conditions and probe arrangements (300 K-1200 K). This paper will describe in detail the apparatus design and instrumentation, including a discussion of its capabilities and accuracy as measured through representative diagnostics. In addition, this paper will emphasize the techniques required to effectively manage uncertainty in high temperature Seebeck coefficient measurements.

Thermoelectric properties of AgGaTe2and related chalcopyrite structure materials

We present an analysis of the potential thermoelectric performance of $p$-type AgGaTe${}_{2}$, which has already shown a $ZT$ of 0.8 with partial optimization, and observe that the same band-structure features, such as a mixture of light and heavy bands and isotropic transport, that lead to this good performance are present in certain other ternary chalcopyrite structure semiconductors. We find that optimal performance of AgGaTe${}_{2}$ will be found for hole concentrations between 4 $\ifmmode\times\else\texttimes\fi{}{10}^{19}$ and 2 $\ifmmode\times\else\texttimes\fi{}{10}^{20}$ cm${}^{\ensuremath{-}3}$ at 900 K, and 2 $\ifmmode\times\else\texttimes\fi{}{10}^{19}$ and 10${}^{20}$ cm${}^{\ensuremath{-}3}$ at 700 K, and that certain other chalcopyrite semiconductors might show good thermoelectric performance at similar doping ranges and temperatures if not for higher lattice thermal conductivity.

Potential Thermoelectric Performance from Optimization of Hole-DopedBi2Se3

The search for efficient and more economical thermoelectric materials is still on and gaining even more urgency after fifty years. Scientists at Oak ridge National Lab show that nanostructured $B\phantom{\rule{0}{0ex}}{i}_{2}\phantom{\rule{0}{0ex}}S\phantom{\rule{0}{0ex}}{e}_{3}$ holds significant promise.

Doping dependence of thermoelectric performance in Mo3Sb7: First-principles calculations

We study the effects of doping Mo3Sb7 with transition metals (Ni,Fe,Co,Ru) via first principles calculations, including electronic structure, lattice dynamics and Boltzmann transport. We find heavy-mass bands and large, rapidly varying density-of-states, generally favorable for high thermopower, near the band gap of this material. Transport calculations predict large Seebeck coefficients exceeding 300 $$\mu$$V/K in a wide temperature range above 500 K (a range suitable for waste heat recovery), if the material can be doped into a semiconducting state. These thermopowers are much higher than those that have previously been experimentally observed; we find that performance exceeding current limits may be found at lower carrier concentration than achieved presently. We also discuss the selection of dopant and the potential thermoelectric performance of optimally doped Mo3Sb7.