• Title/Summary/Keyword: thermoelectric properties

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Thermoelectric Properties of Porous Mg3Sb2 Based Compounds Fabricated by Reactive Liquid Phase Sintering (반응성 액상 소결법으로 제조한 다공성 Mg3Sb2계 화합물의 열전물성)

  • Jang, Kyung-Wook;Kim, In-Ki;Kim, Il-Ho
    • Korean Journal of Materials Research
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    • v.25 no.2
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    • pp.68-74
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    • 2015
  • The porous $Mg_3Sb_2$ based compounds with 60~70% of relative density were prepared by powder compaction at room temperature and reactive liquid phase sintering at 1023 K for 4hrs. The stoichiometric $Mg_3Sb_2$ compounds were synthesized from elemental Sb and Mg powder in the mixing range of 61~63 at% Mg. The increased scattering effect due to the micro-pores reduced the mobility of the charge carrier and the phonon, which caused the electrical conductivity and the thermal conductivity to decrease, respectively. But the scattering effect was greater for the electrical conductivity than for the thermal conductivity. Excess Mg alloyed in the $Mg_3Sb_2$ compounds decreased the electrical conductivity, but had no effect on the thermal conductivity. On the other hand, the large increase of the Seebeck coefficient was the result of a decrease in the charge carrier density due to the excess Mg. Dimensionless figure of merit of the porous $Mg_3Sb_2$ compound reached a maximum value of 0.28 at 61 at% Mg. The obtained value was similar to that of $Mg_3Sb_2$ compounds having little pores.

First-principles Study on the Magnetic Properties of Gd doped Bithmuth-Telluride (Gd 도핑된 비스무스 텔루라이드의 자기적 성질에 대한 제일원리 계산 연구)

  • Van Quang, Tran;Kim, Miyoung
    • Journal of the Korean Magnetics Society
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    • v.26 no.2
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    • pp.39-44
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    • 2016
  • Determination of the structural, electronic, and magnetic properties of the magnetically doped bismuth-telluride alloys are drawing lots of interest in the fields of the thermoelectric application as well as the research on magnetic interaction and topological insulator. In this study, we performed the first-principles electronic structure calculations within the density functional theory for the Gd doped bismuth-tellurides in order to study its magnetic properties and magnetic phase stability. All-electron FLAPW (full-potential linearized augmented plane-wave) method is employed and the exchange correlation potentials of electrons are treated within the generalized gradient approximation. In order to describe the localized f-electrons of Gd properly, the Hubbard +U term and the spin-orbit coupling of the valence electrons are included in the second variational way. The results show that while the Gd bulk prefers a ferromagnetic phase, the total energy differences between the ferromagnetic and the antiferromagnetic phases of the Gd doped bismuth-telluride alloys are about ~1meV/Gd, indicating that the stable magnetic phase may be changed sensitively depending on the structural change such as defects or strains.

Crystallization behavior and thermoelectric properties of p-type $(Bi_{1-X}Sb_X)_2Te_3$ thin films prepared by magnerron sputtering (마그네트론 스퍼터링법으로 제조한 P형 $(Bi_{1-X}Sb_X)_2Te_3$ 박막의 결정성과 열전특성)

  • 연대중;오태성
    • Journal of the Korean Vacuum Society
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    • v.9 no.4
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    • pp.353-359
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    • 2000
  • $(Bi_{0.15}Sb_{0.85})_2Te_3$ and $(Bi_{1-x}Sb_x)_2Te_3$ thermoelectric thin films were prepared by magnetron sputtering process, and their thermoelectric characteristics were investigated with variation of the sputtering condition and the $Sb_2Te_3$ content. The $(Bi_{0.15}Sb_{0.85})_2Te_3$ film, deposited by DC sputtering at $300^{\circ}C$ with rotating the Corning glass substrate at 10 rpm, was fully crystallized to $(Bi,Sb)_2Te_3$ phase with c-axis preferred orientation. This $(Bi_{0.15}Sb_{0.85})_2Te_3$ film exhibited the Seebeck coefficient of 185 $\mu$V/K which was higher than the values of other $(Bi_{0.15}Sb_{0.85})_2Te_3$ films fabricated with different sputtering conditions. With increasing the $Sb_2Te_3$ content, the Seebeck coefficient and electrical resistivity of p-type $(Bi_{1-x}Sb_x)_2Te_3$ (0.77$\leq$x$\leq$1.0) film were lowered. Among p-type $(Bi_{1-x}Sb_x)_2Te_3$ films, a maximum power factor of $0.79{\times}10^{-3}W/K^2-m$ was obtained at (Bi_{0.05}Sb_{0.95})_2Te_3$ composition..

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Thermal Property of 2D-Disordered Tungsten Chalcogenides (2차원적으로 무질서화된 텅스텐 칼코겐화물의 열적특성에 관한 연구)

  • Kim, Jong-Young;Jang, Kyoung-Ju;Pee, Jae-Hwan;Cho, Kwang-Yeon;Choi, Soon-Mok;Seo, Won-Sun;Kim, Kyung-Ja
    • Journal of the Korean Ceramic Society
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    • v.47 no.2
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    • pp.132-135
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    • 2010
  • Thermal properties of layered metal chalcogenides such as $WT_2$ (T=S,Se) with two-dimensionally disordered structure were evaluated. Thermal conductivity shows a marked decrease after exfoliation and subsequent restacking because of random stacking of two-dimensional crystalline sheet, which circumvents thermal conduction pathways along longitudinal direction in anisotropic materials.

Analysis of Electromotive Force Characteristics for Electromagnetic Energy Harvester using Ferrofluid

  • Kim, Young Sun
    • Journal of Magnetics
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    • v.20 no.3
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    • pp.252-257
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    • 2015
  • This paper investigates the concept and implementation of an energy harvesting device using a ferrofluid sloshing movement to generate an electromotive force (EMF). Ferrofluids are often applied to energy harvesting devices because they have both magnetic properties and fluidity, and they behave similarly to a soft ferromagnetic substance. In addition, a ferrofluid can change its shape freely and generate an EMF from small vibrations. The existing energy harvesting techniques, for example those using piezoelectric and thermoelectric devices, generate minimal electric power, as low as a few micro-watts. Through flow analysis of ferrofluids and examination of the magnetic circuit characteristics of the resultant electromagnetic system, an energy harvester model based on an electromagnetic field generated by a ferrofluid is developed and proposed. The feasibility of the proposed scheme is demonstrated and its EMF characteristics are discussed based on experimental data.

A study on the thermal analysis of resistance sport welding Process using a FEM method (FEM 방법을 이용한 저항 점용접 공정의 열분석에 관한 연구)

  • Kim, Ill-Soo;Hou Zhigang;Wang Yuanxun;Li Chunzhi;Chen Chuanyao
    • Proceedings of the KWS Conference
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    • 2003.11a
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    • pp.172-174
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    • 2003
  • In this paper, a 2D axisymmetric model of thermoelectric Finite Element Method (FEM) is developed to analyze the transient thermal behavior of Resistance Spot Welding (RSW) process using commercial software, called ANSYS. The determination of the contact resistance at the faying surface is moderately simplified to reduce the calculating time, while the temperature dependent material properties, phase change and convectional boundary conditions are taken account fur the improvement of the calculated accuracy. The thermal history of the whole process (including cooling) and temperature distributions for any position in the weldment is obtained through the analysis.

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Thermoelectric and electrical properties of In-Sn-Zn-O thin films deposited by magnetron co-sputtering (이원 동시 마그네트론 스퍼터링법을 이용하여 증착한 In-Sn-Zn-O 박막의 열전 특성)

  • Byeon, Ja-Yeong;Song, Pung-Geun
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2015.11a
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    • pp.297-298
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    • 2015
  • 우수한 열전 성능의 소자가 되기 위해서는 높은 전기 전도도 및 제백상수 그리고 낮은 열 전도도를 가져야한다. 본 연구에서는 DC 마그네트론 스퍼터링 법을 이용하여 비정질 구조를 갖는 ITZO 박막을 제작하였으며, 전기적 특성과 열전 특성을 조사하였다. 그 결과 ITO에 ZnO 첨가시 전기적 특성 및 열전 특성이 향상 되었다. 또한 비정질 구조를 가지므로 격자에 의한 열 전도도가 낮아 전체 열 전도도가 낮을 것이며 이는 높은 열전 성능 지수(ZT)를 가질 것이라 예상된다.

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Thermoelectric and electrical properties of amrophous IZO and crystalline ITO thin films (DC 마그네트론 스퍼터링법으로 증착한 비정질 IZO와 결정질 ITO박막의 열전 특성)

  • Byeon, Ja-Yeong;Kim, Seo-Han;Song, Pung-Geun
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2016.11a
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    • pp.159-159
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    • 2016
  • 세계적으로 대체 에너지는 중요한 이슈가 되고 있으며, 이들 중 열전 재료는 열 에너지를 전기 에너지로 바꿀 수 있는 열전 재료가 각광 받고 있다. 그 중, 박막 형태의 열전 재료는 벌크 형태에 비해 나노 구조화가 용이하여 열전 특성을 향상 시킬 수 있는 잠재력을 지니고 있다. 특히, 박막형 열전 소자는 정밀 온도 제어가 가능하며, 소형화 기기의 응용이 가능하여, 고 직접화 전자 소자의 발열 문제를 해결 할 수 있어 더욱 주목 받고 있다. 박막형 열전소자 중 산화물 반도체계에 대한 연구가 활발히 진행되고 있으며, 이러한 산화물 반도체는 기존의 화합물 반도체인 Pb-Te, Bi-Te 등의 기존의 재료에 비해 낮은 독성을 가진다. 또한, 고온에서 열적 안정성이 우수하여 고온에서 적용 가능하다는 장점을 가진다. 열전재료의 효율은 열전 성능 지수(ZT)와 Power factor(PF)로 평가된다.

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Thermoelectric Properties of n-type $\textrm{Bi}_{2}\textrm{Te}_{2.4}\textrm{Se}_{0.6}$ Prepared by Novel Sintering Process (새로운 소결 방법으로 제조된 n형 $\textrm{Bi}_{2}\textrm{Te}_{2.4}\textrm{Se}_{0.6}$열전재료의 특성)

  • Son, Seok-Ho;Jang, Gyeo-Uk;Lee, Dong-Hui
    • Korean Journal of Materials Research
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    • v.7 no.5
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    • pp.374-380
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    • 1997
  • 열전재료 분말을 AI관에 진공봉입하고 형틀가입한 후 소결하는 새로운 방법으로 n형 B $i_{2}$T $e_{2.4}$S $e_{0.6}$를 제조하여 소결조건에 따른 소결성과 열전특성을 조사.분석하였다. AI은 소결시 열전재료와 반응하지 않아 보호 용기로 적합하였으며, 평균입도 195$\mu\textrm{m}$의 분말을 사용하여 성형압 280 MPa, 온도 400에서 50$0^{\circ}C$에서 소결할 경우 성능지수는 1.9x $10^{-3}$K였다.다.

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Single Crystal Growth and Magnetic Properties of Mn-doped Bi2Se3 and Sb2Se3

  • Choi, Jeong-Yong;Lee, Hee-Woong;Kim, Bong-Seo;Choi, Sung-Youl;Choi, Ji-Youn;Cho, Sung-Lae
    • Journal of Magnetics
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    • v.9 no.4
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    • pp.125-127
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    • 2004
  • We have grown Mn-doped $Bi_2Se_3$ and $Sb_2Se_3$ single crystals using the temperature gradient solidification method. We report on the structural and magnetic propertis of Mn-doped $Bi_2Se_3$ and $Sb_2Se_3$ compound semi-conductors. The lattice constants of several percent Mn-doped $Bi_2Se_3$ and $Sb_2Se_3$ were slightly smaller than those of the un-doped samples due to the smaller Mn atomic radius ($1.40 {\AA}$) than those of Bi ($1.60 {\AA}$) and Sb ($1.45 {\AA}$). Mn-doped $Bi_2Se_3$ and $Sb_2Se_3$ showed spin glass and paramagnetic properties, respectively.