Thermoelectric Conversion Applications Research Articles

A biomass hydrogel solar evaporator based on low-grade tobacco leaves for water evaporation and thermoelectric conversion applications

A low-cost and eco-friendly solar steam generator was designed by combining polyvinyl alcohol hydrogels with low-grade tobacco leaves biomass photothermal materials, which apply for water evaporation and thermoelectric conversion.

Exploring electrical property improvement for thermoelectric sulfides

Metal sulfides have been the subject of extensive research as a promising candidate in the study of thermoelectric energy transfer due to their eco-friendly abundance and similarities in chemical and structural properties with tellurides and selenides. Their intrinsically low thermal conductivity decouples the intercorrelated thermoelectric parameters that comprise the figure merit of ZT. This perspective aims to further advance thermoelectric sulfides application in structural designing, performance optimization and mechanism analysis, providing new insights to explore their electrical properties. The influence of chemical modification, heterogeneous phase mixture, and multi-physical technologies for matrix on electrical transport is used to demonstrate the performance improvement for thermoelectric sulfides. Lastly, key outcomes along with future thermoelectric conversion applications are outlined.

Dimensionality reduction induced synergetic optimization of the thermoelectric properties in Bi2Si2X6 (X = Se, Te) monolayers.

Different from three-dimensional bulk compounds, two-dimensional monolayer compounds exhibit much better thermoelectric performance on account of the quantum confinement and interface effect. Here, we present a systematic study on the electronic and thermal transport properties of bulk and monolayer Bi2Si2X6 (X = Se, Te) through theoretical calculations using density functional theory based on first-principles and Boltzmann transport theory. Monolayer Bi2Si2X6 are chemically, mechanically and thermodynamically stable semiconductors with suitable band gaps, and they have lower lattice thermal conductivity (κL) in the a/b direction than their bulk counterparts. The calculated κL of monolayer Bi2Si2Se6 (Bi2Si2Te6) is as low as 0.72 (0.95) W m-1 K-1 at 700 K. Moreover, monolayer Bi2Si2X6 exhibit a higher Seebeck coefficient compared with bulk Bi2Si2X6 owing to the sharper peaks in the electronic density of states (DOS). This results in a significant increase in power factor by dimensionality reduction. Combined with the synergetically suppressed thermal conductivity, the maximum ZT values for monolayer Bi2Si2Se6 and Bi2Si2Te6 are significantly enhanced up to 5.03 and 2.87 with p-type doping at 700 K, which are more than 2 times that of the corresponding bulk compounds. These results demonstrate the superb thermoelectric performance of monolayer Bi2Si2X6 for promising thermoelectric conversion applications.

Layered Tin Chalcogenides SnS and SnSe: Lattice Thermal Conductivity Benchmarks and Thermoelectric Figure of Merit.

Tin sulfide (SnS) and tin selenide (SnSe) are attractive materials for thermoelectric conversion applications. Favorable small band gap, high carrier mobility, large Seebeck coefficient, and remarkably low lattice thermal conductivity are a consequence of their anisotropic crystal structure of symmetry Pnma, made of corrugated, black phosphorus-like layers. Their internal lattice dynamics combined with chemical bond softening in going from SnS to SnSe make for subtle effects on lattice thermal conductivity. Reliable prediction of phonon transport for these materials must therefore include many-body effects. Using first principles methods and a transferable tight-binding potential for frozen phonon calculations, here, we investigate the evolution of thermal lattice conductivity and thermoelectric figure of merit in Pnma-SnS and -SnSe, also including the high-temperature Cmcm-SnS phase. We show how thermal conductivity lowering in SnS at higher temperatures is largely due to dynamic phonon softening ahead of the Pnma–Cmcm structural phase transition. SnS becomes more similar to SnSe in its lifetime and mean free path profiles as it approaches its high-temperature Cmcm phase. The latter nonetheless intrinsically constraints phonon group velocity modules, preventing SnS to overtake SnSe. Our analysis provides important insights and computational benchmarks for optimization of thermoelectric materials via a more efficient computational strategy compared to previous ab initio attempts, one that can be easily transferred to larger systems for further thermoelectric materials nanoengineering. The good description of anharmonicity at higher temperatures inherent to the tight-binding potential yields calculated lattice conductivity values that are in very good agreement with experiments.

Exploring Thermoelectric Property Improvement for Binary Copper Chalcogenides

Copper chalcogenides have been the subject of extensive research as promising candidates in thermoelectric conversion applications due to their advantageous properties, environmental compatibility, and abundance. The low intrinsic thermal conductivity and high electric conductivity of these materials are born out of the “phonon-liquid electron-crystal” structure between the copper and chalcogens. In this review, strategies for thermoelectric property improvement of copper chalcogenides are discussed. The challenges and the future development of binary copper chalcogenides for further thermoelectric conversion applications are outlined.

Thermoelectric properties of stannite-phase CuZn2AS4 (CZAS; A=Al, Ga and In) nanocrystals for solar energy conversion applications

The current study aimed to comprehensively investigate structural, electronic, optical and transport properties of quaternary semiconductor CuZn2AS4 (CZAS; A=Al, Ga and In) nanocrystals (NCs). Based on energy considerations, the stannite structure (I-42m; No. 121) is found to be more stable than the kesterite (I-4; No.82) and wurtzite (P63mc; No.186) type structures. By means of hybrid functional calculations, these nanocrystals have direct band gap of 0.81–1.71 eV with a high absorption coefficient of >104 cm−1, which are well-suited for use in solar energy-conversion applications. Some of the latest advances in applications of these nanocrystals in thermoelectric applications are also highlighted in the current study. It is observed that transport coefficients of these materials are found to be nearly direction independent and isotropic. All three samples are p-type conductors at room temperature. Especially, the Seebeck coefficient of CuZn2AlS4 is even larger than that of CuZn2GaS4 and CuZn2InS4 under the studied carrier concentration and temperature region. The maximum figure of merit (ZT) reaches 0.982 (0.977), 0.984 (0.974) and 0.53 (0.955) for p-type (n-type) CuZn2AlS4, CuZn2GaS4, and CuZn2InS4, respectively, at 300 K. The high Seebeck coefficients, high figure of merit and low thermal conductivities make these systems good candidates for high-efficiency thermoelectric conversion applications.

Transport properties of the SnBi2Te4–PbBi2Te4 solid solution

We report on the electrical and thermal transport properties of the Sn1−xPbxBi2Te4 series and we discuss the potential of these materials for thermoelectric conversion applications. From the evolution of the XRD patterns, we can confidently conclude that a complete solid solution exists between SnBi2Te4 and PbBi2Te4, with no miscibility gap. A crossover from p-type conduction in Sn-rich samples to n-type conduction in Pb-rich ones has been observed, with a transition between x=0.3 and 0.4. A concomitant increase of the electrical resistivity and of the Seebeck coefficient has been observed in the solid solution, which leads to almost constant values of the thermoelectric power factor. Moreover, the thermal conductivity is slightly reduced in the solid solution. The best figure of merit ZT values at room temperature have been observed for p-type Sn0.8Pb0.2Bi2Te4 with ZT=0.25 and for n-type Sn0.3Pb0.7Bi2Te4 with ZT=0.15.

열분해와 Hot Injection법을 이용한 CoSb3나노분말합성

CoSb₃ with its high electrical conductivity, Seebeck coefficient and rather low thermal conductivity is quite a promising material for thermoelectric conversion applications. A potentially high figure of merit (ZT) can be achieved by a nanostructure evolution of thermoelectric materials. In this work, CoSb₃ nanoparticles were synthesized through a thermal decomposition method in cooperation with a hot injection technique. Nano-sized CoSb₃ particles were obtained through the thermal decomposition reaction between the pre-heated cobalt-oleate at 320℃ and the injected antimony oleate with room temperature. The results showed that the particle size was increased with increasing synthesis temperature and the crystallinity of particles was improved with temperature but the decomposition of CoSb₃ was observed at 320℃. The CoSb₃ particles synthesized at 300℃ showed a high purity and an homogeneous shape with average particle size of 26 nm.

Single crystal flux growths of thermoelectric materials

We review recent achievements in single crystal flux growths for selected families of novel candidate materials for thermoelectric conversion applications, and the resulting contributions towards a better understanding of the physical mechanisms involved in optimizing their intrinsic thermoelectric figures of merit, ZT. We also take the opportunity to compile a small list of tips and tricks that we and other researchers have developed over the years to facilitate or optimize flux growths in general – those finer details that do not normally make it into mainstream research publications.

Cross-plane thermal conductivity of superlattices with rough interfaces using equilibrium and non-equilibrium molecular dynamics

This paper describes a heat transfer study of binary Lennard Jones superlattices, focusing on the influence of interface topology on cross-plane thermal conductivity, by using both non-equilibrium and equilibrium molecular dynamics methods. Both methods reveal the same trends of thermal conductivity. In particular, interfacial roughness is shown to slightly increase cross-plane thermal conductivity in comparison to smooth interfaces. Our results highlight paths for optimizing superlattices for thermoelectric conversion applications and for thermal management solutions in micro- and nano-systems.

Highly textured Bi2Te3-based materials for thermoelectric energy conversion

This work is concerned with Bi2Te3-based compounds known as being highly effective materials for thermoelectric applications near room temperature. These compounds are characterized by a remarkable anisotropy linked to their R3¯m crystal structure. Two textured p-type Bi0.4Sb1.6Te3 samples were prepared using a powder metallurgy approach, with the c axis parallel to the pressing direction. One sample was undoped while the second was doped with Pb which acts as an acceptor. The electrical conductivity, Hall coefficient, and magnetoresistivity were measured from room temperature down to 6K. The Seebeck coefficient α and electrical conductivity σ were measured along and perpendicular to the c axis from 300 up to 550K, and the thermal conductivity κ was measured at 300K. Different values of Seebeck coefficient were observed along and perpendicular to the c axis at temperatures above Ti, the beginning of intrinsic region in which the influence of the minority carriers becomes significant. Below Ti, the Seebeck coefficient was isotropic. The maximal power factor P=α2σ, calculated on the basis of the experimental results, was about 40μWcm−1K−2 for the direction perpendicular to the c axis. The thermal conductivity values for the temperature domain above 300K were calculated on the basis of a physical model and the measured values at 300K. The calculated values of the figure of merit Z=P∕κ were 3×10−3 and 2×10−3K−1 at 300 and 400K for the two samples, respectively. These values are comparable to those observed in Bi2Te3-based single crystals, thus making the powder metallurgy approach appropriate for thermoelectric conversion applications.

Enhancement of flip-chip fatigue life by encapsulation : Darbha Suryanarayana, Richard Hsiao, Thomas P. Gall and Jack M. McCreary. IEEE Trans. Compon. Hybrids mfg Technol.14(1), 218 (1991)

We report on the electrical and thermal transport properties of the Sn1−xPbxBi2Te4 series and we discuss the potential of these materials for thermoelectric conversion applications. From the evolution of the XRD patterns, we can confidently conclude that a complete solid solution exists between SnBi2Te4 and PbBi2Te4, with no miscibility gap. A crossover from p-type conduction in Sn-rich samples to n-type conduction in Pb-rich ones has been observed, with a transition between x=0.3 and 0.4. A concomitant increase of the electrical resistivity and of the Seebeck coefficient has been observed in the solid solution, which leads to almost constant values of the thermoelectric power factor. Moreover, the thermal conductivity is slightly reduced in the solid solution. The best figure of merit ZT values at room temperature have been observed for p-type Sn0.8Pb0.2Bi2Te4 with ZT=0.25 and for n-type Sn0.3Pb0.7Bi2Te4 with ZT=0.15.