Enhancement of thermoelectric properties in liquid-phase sintered Te-excess bismuth antimony tellurides prepared by hot-press sintering

Kim, Yun Min; Lydia, R.; Kim, Jinhee; Lin, Chan-Chieh; Ahn, Kyunghan; Rhyee, Jong‐Soo

doi:10.1016/j.actamat.2017.06.036

Cited by 40 publications

(28 citation statements)

References 28 publications

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“…The room‐temperature electrical conductivity of the BST:T film is 42% higher than that of the BST film. It is believed that the tellurium addition results in: I) diminished carrier scattering due to improved interfacial connections between BST particles, and II) an increased carrier (hole) concentration consistent with previous reports, which is closely related to the modulation of antisites (Sb Te‐ and Bi Te‐ ) and anion vacancy (V Te 2+ ) defects in the BST matrix . In order to confirm the change of carrier concentration and mobility, room‐temperature Hall measurements were performed on a series of flexible films.…”

Section: Resultssupporting

confidence: 78%

Flexible Thermoelectric Devices of Ultrahigh Power Factor by Scalable Printing and Interface Engineering

Varghese

Dun

Kempf

et al. 2019

Adv Funct Materials

119

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Printing is a versatile method to transform semiconducting nanoparticle inks into functional and flexible devices. In particular, thermoelectric nanoparticles are attractive building blocks to fabricate flexible devices for energy harvesting and cooling applications. However, the performance of printed devices are plagued by poor interfacial connections between nanoparticles and resulting low carrier mobility. While many rigid bulk materials have shown a thermoelectric figure of merit ZT greater than unity, it is an exacting challenge to develop flexible materials with ZT near unity. Here, a scalable screen-printing method to fabricate high-performance and flexible thermoelectric devices is reported. A tellurium-based nanosolder approach is employed to bridge the interfaces between the BiSbTe particles during the postprinting sintering process. The printed BiSbTe flexible films demonstrate an ultrahigh room-temperature power factor of 3 mW m −1 K −2 and ZT about 1, significantly higher than the best reported values for flexible films. A fully printed thermoelectric generator produces a high power density of 18.8 mW cm −2 achievable with a small temperature gradient of 80 °C. This screen-printing method, which directly transforms thermoelectric nanoparticles into high-performance and flexible devices, presents a significant leap to make thermoelectrics a commercially viable technology for a broad range of energy harvesting and cooling applications.

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Section: Resultssupporting

confidence: 78%

Flexible Thermoelectric Devices of Ultrahigh Power Factor by Scalable Printing and Interface Engineering

Varghese

Dun

Kempf

et al. 2019

Adv Funct Materials

119

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“…Such high electrical conductivities have been previously measured in samples processed in an excess of tellurium and have been related to two main factors: 23,26 i) an increase (over materials with similar Bi/Sb ratios) of the hole concentration associated to a modification of the antisite and vacancy defects due to the tellurium excess; ii) formation during the liquid phase sintering of semicoherent grain boundaries having a minimal effect on hole scattering. 23 Hall measurements of a series of hot-pressed Bi0.5Sb1.5Te3 nanomaterials showed the charge carrier concentrations to be around 54 x10 19 cm -3 , i.e.…”

mentioning

confidence: 64%

Crystallographically Textured Nanomaterials Produced from the Liquid Phase Sintering of Bi_xSb_2–xTe₃ Nanocrystal Building Blocks

et al. 2018

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Bottom-up approaches for producing bulk nanomaterials have traditionally lacked control over the crystallographic alignment of nanograins. This limitation has prevented nanocrystal-based nanomaterials from achieving optimized performances in numerous applications. Here we demonstrate the production of nanostructured Bi SbTe alloys with controlled stoichiometry and crystallographic texture through proper selection of the starting building blocks and the adjustment of the nanocrystal-to-nanomaterial consolidation process. In particular, we hot pressed disk-shaped Bi SbTe nanocrystals and tellurium nanowires using multiple pressure and release steps at a temperature above the tellurium melting point. We explain the formation of the textured nanomaterials though a solution-reprecipitation mechanism under a uniaxial pressure. Additionally, we further demonstrate these alloys to reach unprecedented thermoelectric figures of merit, up to ZT = 1.96 at 420 K, with an average value of ZT = 1.77 for the record material in the temperature range 320-500 K, thus potentially allowing up to 60% higher energy conversion efficiencies than commercial materials.

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“…For p‐type (Bi,Sb) 2 Te 3 materials, a peak zT > 1.2 can be readily realized by nanostructuring 4d,i,6. Recently, the liquid‐phase sintering (LPS) process, which involves sintering under conditions where solid grains are surrounded by the wetting liquid, is also successfully applied to enhance the TE properties of p‐type Bi 2 Te 3 ‐based alloys 2a,4e,8. Nanoscale defects such as dense dislocations4e or Sb‐rich region8b could be introduced during LPS and play important roles in reducing κ L .…”

Section: Introductionmentioning

confidence: 99%

Liquid‐Phase Hot Deformation to Enhance Thermoelectric Performance of n‐type Bismuth‐Telluride‐Based Solid Solutions

Zhang

et al. 2019

Advanced Science

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Bismuth‐telluride‐based solid solutions are the best commercial thermoelectric materials near room temperature. For their n‐type polycrystalline compounds, the maximum figures of merit (zTs) are often less than 1.0 due to the degraded carrier mobility resulting from the loss of texture. Herein, a liquid‐phase hot deformation procedure, during which the Bi2(Te,Se)3 ingots are directly hot deformed with the extrusion of liquid eutectic phase, is performed to enhance the thermoelectric performance of n‐type Bi2(Te,Se)3 alloys. The deformation‐induced dynamic recrystallization is remarkably suppressed due to the reduction of nucleation sites and the release of deformation stress by liquid phase, contributing to a weakened carrier scattering and enhanced carrier mobility. The liquid eutectic phase also facilitates the rotation of grains and enhanced (000l) texture, further improving carrier mobility. In addition, the dense dislocations and lattice distortion introduced into the matrix reduce the lattice thermal conductivity. As a result, a high zT value of 1.1 at 400 K is obtained, about 75% increment over the normal one‐step hot deformed alloys. This work not only demonstrates a simple and efficient technique for achieving superior n‐type Bi2Te3‐based materials, but also elucidates the important role of liquid eutectic phase in hot deformation.

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Enhancement of thermoelectric properties in liquid-phase sintered Te-excess bismuth antimony tellurides prepared by hot-press sintering

Cited by 40 publications

References 28 publications

Flexible Thermoelectric Devices of Ultrahigh Power Factor by Scalable Printing and Interface Engineering

Flexible Thermoelectric Devices of Ultrahigh Power Factor by Scalable Printing and Interface Engineering

Crystallographically Textured Nanomaterials Produced from the Liquid Phase Sintering of Bi_xSb_2–xTe₃ Nanocrystal Building Blocks

Liquid‐Phase Hot Deformation to Enhance Thermoelectric Performance of n‐type Bismuth‐Telluride‐Based Solid Solutions

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Enhancement of thermoelectric properties in liquid-phase sintered Te-excess bismuth antimony tellurides prepared by hot-press sintering

Cited by 40 publications

References 28 publications

Flexible Thermoelectric Devices of Ultrahigh Power Factor by Scalable Printing and Interface Engineering

Flexible Thermoelectric Devices of Ultrahigh Power Factor by Scalable Printing and Interface Engineering

Crystallographically Textured Nanomaterials Produced from the Liquid Phase Sintering of BixSb2–xTe3 Nanocrystal Building Blocks

Liquid‐Phase Hot Deformation to Enhance Thermoelectric Performance of n‐type Bismuth‐Telluride‐Based Solid Solutions

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Crystallographically Textured Nanomaterials Produced from the Liquid Phase Sintering of Bi_xSb_2–xTe₃ Nanocrystal Building Blocks