• Korean Journal of Materials Research
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• v.15 no.10
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• pp.667-670
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• 2005

Binary skutterudite $CoSb_3$ compounds were prepared by the arc melting and hot pressing processes and their thermoelectric properties were investigated in the range from 300 to 600 K. Annealing effect was correlated to phase transformation and homogenization. Thermoelectric properties of the arc-melted and hot-pressed $CoSb_3$ were discussed and compared. Undoped intrinsic $CoSb_3$ prepared by the arc melting showed p-type conduction, while it showed metallic behavior with increasing measuring temperature. However, hot pressed specimens showed n-type conduction, possibly due to Sb evaporation. Thermoelectric properties were remarkably improved by annealing In vacuum and they were closely related to phase transformation.

• Korean Journal of Materials Research
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• v.22 no.6
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• pp.280-284
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• 2012

Bismuth antimony telluride (BiSbTe) thermoelectric materials were successfully prepared by a spark plasma sintering process. Crystalline BiSbTe ingots were crushed into small pieces and then attrition milled into fine powders of about 300 nm ~ 2${\mu}m$ size under argon gas. Spark plasma sintering was applied on the BiSbTe powders at 240, 320, and $380^{\circ}C$, respectively, under a pressure of 40 MPa in vacuum. The heating rate was $50^{\circ}C$/min and the holding time at the sintering temperature was 10 min. At all sintering temperatures, high density bulk BiSbTe was successfully obtained. The XRD patterns verify that all samples were well matched with the $Bi_{0.5}Sb_{1.5}Te_{3}$. Seebeck coefficient (S), electric conductivity (${\sigma}$) and thermal conductivity (k) were evaluated in a temperature range of $25{\sim}300^{\circ}C$. The thermoelectric properties of BiSbTe were evaluated by the thermoelectric figure of merit, ZT (ZT = $S^2{\sigma}T$/k). The grain size and electric conductivity of sintered BiSbTe increased as the sintering temperature increased but the thermal conductivity was similar at all sintering temperatures. Grain growth reduced the carrier concentration, because grain growth reduced the grain boundaries, which serve as acceptors. Meanwhile, the carrier mobility was greatly increased and the electric conductivity was also improved. Consequentially, the grains grew with increasing sintering temperature and the figure of merit was improved.

• Korean Journal of Materials Research
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• v.20 no.6
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• pp.326-330
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• 2010

$CoSb_3$ Skutterudites materials have high potential for thermoelectric application at mid-temperature range because of their superior thermoelectric properties via control of charge carrier density and substitution of foreign atoms. Improvement of thermoelectric properties is expected for the ternary solid solution developed by substitution of foreign atoms having different valances into the $CoSb_3$ matrix. In this study, ternary solid solutions with a stoichiometry of $Co_{1-x}Ni_xSb_3$ x = 0.01, 0.05, 0.1, 0.2, $CoSb_{3-y}Te_y$, y = 0.1, 0.2, 0.3 were prepared by the Spark Plasma Sintering (SPS) system. Before the SPS synthesis, the ingots were synthesized by vacuum induction melting and followed by annealing. For phase analysis X-ray powder diffraction patterns were checked. All the samples were confirmed as single phase; however, with samples that were more doped than the solubility limit some secondary phases were detected. All the samples doped with Ni and Te atoms showed a negative Seebeck coefficient and their electrical conductivities increased with the doping amount up to the solubility limit. For the samples prepared by SPS the maximum value for dimensionless figure of merit reached 0.26, 0.42 for $Co_{0.9}Ni_{0.1}Sb_3$, $CoSb_{2.8}Te_{0.2}$ at 690 K, respectively. These results show that the SPS method is effective in this system and Ni/Te dopants are also effective for increasing thermoelectric properties of this system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.1
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• pp.43-49
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• 2015

In recent years, the amount of heat generated inside of the computer has more increased because of high performance, multi-function, miniaturization and light weight. It is necessary to control the effective heat generation to improve performance and life extension of the computer. In this study, thermoelectric cooling system was manufactured using thermoelectric module and was attached to computer in order to control the heat generated inside computer. And the temperature distributions inside computer were experimentally measured and compared with and without thermoelectric cooling system to investigate the effect of cooling system. Also, to estimate the new cooling system which can substitute for the existing computer cooling system, temperature distributions inside computer were calculated by numerical analysis when there was no cooling system and was applied only cooling system to computer.

• Journal of the Korean Ceramic Society
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• v.40 no.6
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• pp.560-565
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• 2003

M-doped (M=Al, Ni) ZnO thermoelectric materials were fully densified at low temperatures of 800∼1,000$^{\circ}C$ and their sintering characteristics and microstructural features were investigated. Electron microscopic analysis showed that the addition of NiO promoted tile formation of solid solution and caused actively grain growth. The addition of A1$_2$O$_3$ prevented the evaporation of pure ZnO at grain boundaries and suppressed the grain growth by the formation of secondary phase. In case of the addition of A1$_2$O$_3$ together with NiO, the specimen showed an excellent microstructure and also the SEM-EBSP (Electron Back-scattered Diffraction Pattern) analysis confirmed that it shows a superior grain boundary distribution to the others specimens. These microstructural characteristics induced by the addition of A1$_2$O$_3$ together with NiO may increase the electrical conductivity by the increase in carrier concentration and decrease the thermal conductivity by the phonon scattering effect and, consequently, improve the thermoelectric property.

• Korean Journal of Materials Research
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• v.32 no.3
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• pp.132-138
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• 2022

Zintl phase Mg₃Sb₂ is a promising thermoelectric material in medium to high temperature range due to its low band gap energy and characteristic electron-crystal phonon-glass behavior. P-type Mg₃Sb₂ has conventionally exhibited lower thermoelectric properties compared to its n-type counterparts, which have poor electrical conductivity. To address these problems, a small amount of Sn doping was considered in this alloy system. P-type Mg₃Sb₂ was synthesized by controlled melting, pulverizing, and subsequent vacuum hot pressing (VHP) method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate phases and microstructure development during the process. Single phase Mg₃Sb₂ was successfully formed when 16 at.% of Mg was excessively added to the system. Nominal compositions of Mg_3.8Sb_2-xSn_x (0 ≤ x ≤ 0.008) were considered in this study. Thermoelectric properties were evaluated in terms of Seebeck coefficient, electrical conductivity, and thermal conductivity. A peak ZT value ≈ 0.32 was found for the specimen Mg_3.8Sb_1.994Sn_0.006 at 873 K, showing an improved ZT value compared to intrinsic one. Transport properties were also evaluated and discussed.

• Composites Research
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• v.34 no.6
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• pp.434-439
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• 2021

Graphene and polyaniline with thermoelectric properties are one of the potential substitutes for inorganic materials for flexible thermoelectric applications. In this study, we studied the photo-induced thermoelectric effect of graphene-polyaniline composites. The graphene-polyaniline composites were synthesized by introducing an amine functional group to graphene oxide for covalently connecting graphene and polyaniline, reducing the graphene oxide, and then polymerizing the graphene oxide with aniline. Graphene-polyaniline composites were prepared by changing the aniline contents in order to expect an optimal photothermoelectric effect, and their structural properties were confirmed through FT-IR and Raman analysis. The photocurrent and photovoltage characteristics were analyzed by irradiating light asymmetrically without an external bias and the current and voltage with various aniline contents. While the photocurrent trends to the electrical conductivity of the graphene-polyaniline composites, the photovoltage was related to the temperature change of the graphene-polyaniline composite, which was converted into thermal energy by light.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.14 no.3
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• pp.29-34
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• 2018

To present the design direction of the thermoelectric module (TEM) refrigerator, analysis of the effect of the design parameters on the energy efficiency and performance of the refrigerator is performed. The design parameters considered are the cooling capacity of the TEM and the heat transfer performance of the heating and cooling surface of the TEM. The heat transfer performance is the most effective design parameter for improving cooling power. The smaller ΔT and cooling capacity of the TEM make the higher efficiency of the refrigerator.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.10a
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• pp.711-712
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• 2009

MCP 기술을 이용한 반도체 칩에서 문제가 되는 방열문제를 해결하기 위한 방법으로 열전 냉각 소자를 이용하여 열을 방출 시키는 방법에 관하여 연구를 수행하였다. 시뮬레이션을 통하여 열전 소자가 작동할 때, 흡수하는 열량을 계산할 수 있었으며, 열전 소자의 냉각 성능도 평가 할 수 있었다. 이러한 열 해석 및 열전 해석을 통하여 적층 구조의 MCP 모듈을 위한 열 설계 및 효율적 냉각을 가능하게 할 수 있을 것이다.

• Journal of the Korean Ceramic Society
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• v.33 no.1
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• pp.74-82
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• 1996

Fe-Si based powders prepare by melting the metals in the composition of FeSi2,.Fe0.95Mn0.05Si2 and Fe0.95Co0.05Si0.2 were used as the starting materials together with a commercial FeSi2 powder to study the effect of oxidation on their thermoelectric properties. The powders were heated at 650~80$0^{\circ}C$ in dired air before forming and sintering at 1190 and 120$0^{\circ}C$ in Ar+7%H2. The microstructure and phases of the annealed specimens were observed using the optical microscopty SEM, EDS and XRD. The thermoelectric properties of the specimens were also measured. The temperature at which Seebe다 coefficient showed the maximum value increased with the degree of oxidation. Electrical conductivity showed a tendency to decrease in the oxidized samples regardless of their compositions. Seebeck coefficient of the specimen showed almost the same value even after oxidation which may be explained by the formation of the discontinuous second phases from impurities in the oxidized specimens.