Effect of spark plasma sintering conditions on the thermoelectric properties of (Bi0.25Sb0.75)2Te3 alloys

Lim, Sang Soon; Kim, Ju Heon; Kwon, Beomjin; Kim, Seong Keun; Park, Hyung Ho; Lee, Ki Suk; Baik, Jeong Min; Choi, Won Jun; Kim, Dong Ik; Hyun, Dow-Bin; Kim, Jin Sang; Baek, Seung Hyub

doi:10.1016/j.jallcom.2016.03.284

Cited by 26 publications

(6 citation statements)

References 29 publications

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“…The size of the Bi 2 Te 2.7 Se 0.3 grains was found to be small, generally below 1 µm. Given that the grains of Bi 2 Te 3 -based alloys generally grow to a larger size after SPS at high temperatures, such as 500 • C [40], this suggests that the ALD of a thin oxide layer effectively suppressed the grain growth during the sintering process. Indeed, it has been previously reported that an extremely low κ value was obtained in the ALD-ZnO-coated Bi 0.4 Sb 1.6 Te 3 , due to the formation of fine grains [38].…”

Section: Resultsmentioning

confidence: 99%

Carrier Modulation in Bi2Te3-Based Alloys via Interfacial Doping with Atomic Layer Deposition

et al. 2020

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The carrier concentration in Bi2Te3-based alloys is a decisive factor in determining their thermoelectric performance. Herein, we propose a novel approach to modulate the carrier concentration via the encapsulation of the alloy precursor powders. Atomic layer deposition (ALD) of ZnO and SnO2 was performed over the Bi2Te2.7Se0.3 powders. After spark plasma sintering at 500 °C for 20 min, the carrier concentration in the ZnO-coated samples decreased, while the carrier concentration in the SnO2-coated samples increased. This trend was more pronounced as the number of ALD cycles increased. This was attributed to the intermixing of the metal ions at the interface. Zn2+ substituted for Bi3+ at the interface acted as an acceptor, while Sn4+ substituted for Bi3+ acted as a donor. This indicates that the carrier concentration can be adjusted depending on the materials deposited with ALD. The use of fine powders changes the carrier concentration more strongly, because the quantity of material deposited increases with the effective surface area. Therefore, the proposed approach would provide opportunities to precisely optimize the carrier concentration for high thermoelectric performance.

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Section: Resultsmentioning

confidence: 99%

Carrier Modulation in Bi2Te3-Based Alloys via Interfacial Doping with Atomic Layer Deposition

et al. 2020

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“…The methods to obtain physical properties of the test materials are described in the Section 3. The test samples are Bi 2 -Te 3 based sintered materials that were prepared in our group either via hot-extrusion technique (type 1 and 2) 17 , or spark plasma sintering (type 3) 18 . To vary the shape factor, we modified either L or A .…”

Section: Overview Of Harman Measurementmentioning

confidence: 99%

Correction of the Electrical and Thermal Extrinsic Effects in Thermoelectric Measurements by the Harman Method

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Roh

Lee

et al. 2016

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Although the Harman method evaluates the thermoelectric figure-of-merit in a rapid and simple fashion, the accuracy of this method is affected by several electrical and thermal extrinsic factors that have not been thoroughly investigated. Here, we study the relevant extrinsic effects and a correction scheme for them. A finite element model simulates the electrical potential and temperature fields of a sample, and enables the detailed analysis of electrical and thermal transport. The model predicts that the measurement strongly depends on the materials, sample geometries, and contact resistance of the electrodes. To verify the model, we measure the thermoelectric properties of Bi2-Te3 based alloys with systematically varied sample geometries and either with a point or a surface current source. By comparing the model and experimental data, we understand how the measurement conditions determine the extrinsic effects, and, furthermore, able to extract the intrinsic thermoelectric properties. A correction scheme is proposed to eliminate the associated extrinsic effects for an accurate evaluation. This work will help the Harman method be more consistent and accurate and contribute to the development of thermoelectric materials.

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“…Test materials are Bi 2 Te 3− x Se x (n-type) and Bi 2− x Sb x Te 3 (p-type) fabricated via various processes such as hot extrusion, spark plasma sintering (SPS)13, and hot press14. As the TE properties such as α , ρ , and k of the materials all affect the PTEs34568910, testing several materials enables to see the link between the PTEs and TE properties, and helps to confirm the validity of the developed method.…”

Section: Sample Preparationmentioning

confidence: 99%

Harman Measurements for Thermoelectric Materials and Modules under Non-Adiabatic Conditions

Roh

Lee

Kang

et al. 2016

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Accuracy of the Harman measurement largely depends on the heat transfer between the sample and its surroundings, so-called parasitic thermal effects (PTEs). Similar to the material evaluations, measuring thermoelectric modules (TEMs) is also affected by the PTEs especially when measuring under atmospheric condition. Here, we study the correction methods for the Harman measurements with systematically varied samples (both bulk materials and TEMs) at various conditions. Among several PTEs, the heat transfer via electric wires is critical. Thus, we estimate the thermal conductance of the electric wires, and correct the measured properties for a certain sample shape and measuring temperature. The PTEs are responsible for the underestimation of the TEM properties especially under atmospheric conditions (10–35%). This study will be useful to accurately characterize the thermoelectric properties of materials and modules.

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Effect of spark plasma sintering conditions on the thermoelectric properties of (Bi0.25Sb0.75)2Te3 alloys

Cited by 26 publications

References 29 publications

Carrier Modulation in Bi2Te3-Based Alloys via Interfacial Doping with Atomic Layer Deposition

Carrier Modulation in Bi2Te3-Based Alloys via Interfacial Doping with Atomic Layer Deposition

Correction of the Electrical and Thermal Extrinsic Effects in Thermoelectric Measurements by the Harman Method

Harman Measurements for Thermoelectric Materials and Modules under Non-Adiabatic Conditions

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