• Title/Summary/Keyword: thermoelectric properties

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Determination of the Thermolelectric Properties of NaxCo2O4 by Controlling the Concentration of Na and Additive (NaxCo2O4의 열전특성에 미치는 Na 함량변화와 첨가제의 효과)

  • Choi, Soon-Mok;Jeong, Seong-Min;Seo, Won-Seon
    • Journal of the Korean Ceramic Society
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    • v.46 no.6
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    • pp.689-694
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    • 2009
  • Layer-structured $Na_xCo_2O_4$ was synthesized from $Na_2CO_3\;and\;Co_3O_4$ powders. The chemical concentrations of Na and additive were controlled to enhance the thermoelectric properties over the temperature range from 400 K to 1,150 K. As a result, we obtained the maximum thermoelectric properties at a single phase region with Na content of x=1.5. When Na content was smaller than x=1.5, the thermoelectric properties was low due to formation of second phases of CoO and other oxides. Additionally, Mn was doped to improve thermoelectric properties by means of decreasing thermal conductivity. The results showed that the concentrations of both Na and Mn are all governing factors to determine the thermoelectric properties of $Na_xCo_2O_4$ system.

Study on Thermoelectric Properties of Cu Doping of Pulse-Electrodeposited n-type Bi2(Te-Se)3 Thin Films (펄스 전기도금법에 의해 제조된 n형 Bi2(Te-Se)3 박막의 Cu 도핑에 따른 열전특성에 관한 연구)

  • Heo, Na-Ri;Kim, Kwang-Ho;Lim, Jae-Hong
    • Journal of the Korean institute of surface engineering
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    • v.49 no.1
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    • pp.40-45
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    • 2016
  • Recently, $Bi_2Te_3$-based alloys are the best thermoelectric materials near to room temperature, so it has been researched to achieve increased figure of merit(ZT). Ternary compounds such as Bi-Te-Se and Bi-Sb-Te have higher thermoelectric property than binary compound Bi-Te and Sb-Te, respectively. Compared to DC plating method, pulsed electrodeposition is able to control parameters including average current density, and on/off pulse time etc. Thereby the morphology and properties of the films can be improved. In this study, we electrodeposited n-type ternary Cu-doped $Bi_2(Te-Se)_3$ thin film by modified pulse technique at room temperature. To further enhance thermoelectric properties of $Bi_2(Te-Se)_3$ thin film, we optimized Cu doping concentration in $Bi_2(Te-Se)_3$ thin film and correlated it to electrical and thermoelectric properties. Thus, the crystal, electrical, and thermoelectric properties of electrodeposited $Bi_2(Te-Se)_3$ thin film were characterized the XRD, SEM, EDS, Seebeck measurement, and Hall effect measurement, respectively. As a result, the thermoelectric properties of Cu-doped $Bi_2(Te-Se)_3$ thin films were observed that the Seebeck coefficient is $-101.2{\mu}V/K$ and the power factor is $1412.6{\mu}W/mK^2$ at 10 mg of Cu weight. The power factor of Cu-doped $Bi_2(Te-Se)_3$ thin film is 1.4 times higher than undoped $Bi_2(Te-Se)_3$ thin film.

Thermoelectric Properties of Co1-xFexSb3 Prepared by Hot Pressing (열간압축성형으로 제조한 Co1-xFexSb3의 열전특성)

  • Park, Kwan-Ho;Ur, Soon-Chul;Kim, Il-Ho
    • Korean Journal of Materials Research
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    • v.16 no.7
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    • pp.435-438
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    • 2006
  • The hot pressing was employed to prepare Fe-doped $CoSb_3$ skutterudites and their thermoelectric properties were investigated. Single phase ${\delta}-CoSb_3$ was successfully obtained by the hot pressing under 60MPa at 773 K for 2 hrs. Iron atoms acted as electron acceptors by substituting cobalt atoms. Thermoelectric properties were remarkably improved by the appropriate doping. $Co_{0.7}Fe_{0.3}Sb_3$ was found as an optimum composition for the best thermoelectric property in this work.

Consolidation of Thermal Electric Material Powder by MPC Process and Thermal Electric Properties (MPC 공정에 의한 열전반도체 분말의 성형 및 열전특성)

  • Yun, J.S.;Koo, J.M.;Kim, T.S.;Hong, S.J.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2009.05a
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    • pp.454-456
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    • 2009
  • N-Type $SbI_3$ doped $95%Bi_2Te_3+5%\;Bi_2Se_3$ compounds were newly fabricated by the combination of gas atomization process and Magnetic Pulsed Compaction process. The thermoelectric properties of the MPCed bulks according to consolidation temperatures were investigated by a combination of microscopy, XRD and thermoelectric property testing. The microstructure of MPCed bulk shows homogeneous and fine distribution through consolidated bulks due to the high solidification of compound powders. The research presented the challenges toward the successful consolidation of thermoelectric powder using magnetic pulsed compaction (MPC) and analysis of thermoelectric properties of the consolidated bulks.

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Optimization of Thermoelectric Elements for Thermoelectric Coolers (열전냉동기용 열전요소의 최적화)

  • Jeong, Eun-Soo
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.24 no.5
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    • pp.409-414
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    • 2012
  • A theoretical investigation to optimize thermoelectric elements for thermoelectric coolers was performed using a new one-dimensional analytic model. Mathematical expressions for the optimum current and the optimum length of a thermoelectric element, which maximize the coefficient of performance of thermoelectric coolers, were obtained. The optimum current is expressed in terms of the cooling load for a thermoelectric element, the hot and cold side temperatures and thermoelectric properties, but not the length of a thermoelectric element. The optimum current is proportional to the cooling load and decreases as the temperature difference between the hot and cold sides decreases. It is also shown that the optimum length of a thermoelectric element decreases as the cooling load increases.

Characteristics of thermal stress for thermoelectric generator with sliding (온도차를 이용한 열전발전기의 sliding에 따른 열응력 특성)

  • Woo, B.C.;Lee, H.W.;Lee, D.Y.;Kim, B.S.;Kim, B.G.;Suh, C.M.
    • Proceedings of the KIEE Conference
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    • 1999.07d
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    • pp.1904-1906
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    • 1999
  • The purpose of this study is to manufacture and test a thermoelectric generator which converts unused energy from close-at-hand sources, such as garbage incineration heat and industrial exhaust, to electricity. A manufacturing process and the properties of a thermoelectric generator are discussed before simulating the thermal stress and thermal properties of a thermoelectric module located between an aluminum tube and alumina plate. It was shown that the electric voltage of a thermoelectric generator with 128 thermoelectric modules was 4.8 voltage per Kelvin, and the longitudinal stresses of an aluminum tube with a two-point constrained tube could be released more than those with a one-point constrained tube.

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Optimized Thermoelectric Properties in Zn-doped Zintl Phase Magnesium-Antimonide

  • Rahman, Md. Mahmudur;Ur, Soon-Chul
    • Korean Journal of Materials Research
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    • v.32 no.6
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    • pp.287-292
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    • 2022
  • Magnesium-antimonide is a well-known zintl phase thermoelectric material with low band gap energy, earth-abundance and characteristic electron-crystal phonon-glass properties. The nominal composition Mg3.8-xZnxSb2 (0.00 ≤ x ≤ 0.02) was synthesized by controlled melting and subsequent vacuum hot pressing method. To investigate phase development and surface morphology during the process, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were carried out. It should be noted that an additional 16 at. % Mg must be added to the system to compensate for Mg loss during the melting process. This study evaluated the thermoelectric properties of the material in terms of Seebeck coefficient, electrical conductivity and thermal conductivity from the low to high temperature regime. The results demonstrated that substituting Zn at Mg sites increased electrical conductivity without significantly affecting the Seebeck coefficient. The maximal dimensionless figure of merit achieved was 0.30 for x = 0.01 at 855 K which is 30% greater than the intrinsic value. Electronic flow properties were also evaluated and discussed to explain the carrier transport mechanism involved in the thermoelectric properties of this alloy system.

The Thermoelectric Properties of p-type SiGe Alloys Prepared by RF Induction Furnace (고주파 진공유도로로 제작한 p형 SiGe 합금의 열전변환물성)

  • 이용주;배철훈
    • Journal of the Korean Ceramic Society
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    • v.37 no.5
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    • pp.432-437
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    • 2000
  • Thermoelectric properties of p-type SiGe alloys prepared by a RF inductive furnace were investigated. Non-doped Si80Ge20 alloys were fabricated by control of the quantity of volatile Ge. The carrier of p-type SiGe alloy was controlled by B-doping. B doped p-type SiGe alloys were synthesized by melting the mixture of Ge and Si containing B. The effects of sintering/annealing conditions and compaction pressure on thermoelectric properties (electrical conductivity and Seebeck coefficient) were investigated. For nondoped SiGe alloys, electrical conductivity increased with increasing temperatures and Seebeck coefficient was measured negative showing a typical n-type semiconductivity. On the other hand, B-doped SiGe alloys exhibited positive Seebeck coefficient and their electrical conductivity decreased with increasing temperatures. Thermoelectric properties were more sensitive to compaction pressure than annealing time. The highest power factor obtained in this work was 8.89${\times}$10-6J/cm$.$K2$.$s for 1 at% B-doped SiGe alloy.

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Direct Solid State Synthesis of Zn4Sb3 by Hot Pressing and Thermoelectric Properties (열간 압축 공정에 의한 Zn4Sb3의 직접 고상 반응 합성 및 열전특성)

  • Ur Soon-Chul
    • Journal of Powder Materials
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    • v.12 no.4 s.51
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    • pp.255-260
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    • 2005
  • Direct solid state synthesis by hot pressing has been applied in order to produce high efficiency $Zn_4Sb_3$ bulk specimens. Single phase $Zn_4Sb_3$ with 98.5% of theoretical density was successfully produced by direct hot pressing of elemental powders containing 1.2 at.% excess Zn. Thermoelectric properties as a function of temperature were investigated from room temperature to 600 K and compared with results of other studies. Transport properties at room temperature were also evaluated. Thermoelectric properties of single phase $Zn_4Sb_3$ materials produced by direct synthesis were measured and are comparable to the published data. Direct solid state synthesis by hot pressing provides a promising processing route in this material.