• Journal of the Microelectronics and Packaging Society
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• v.19 no.1
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• pp.33-38
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• 2012

An in-plane thermoelectric sensor was processed on a glass substrate by evaporation of the n-type Bi-Te and p-type Sb-Te thin films, and its sensing characteristics were evaluated. The n-type Bi-Te thins film used to fabricate the inplane sensor exhibited a Seebeck coefficient of -165 ${\mu}V$/K and a power factor of $80{\times}10^{-4}W/K^2-m$. The p-type Sb-Te thin film used to fabricate the in-plane sensor exhibited a Seebeck coefficient of 142 ${\mu}V$/K and a power factor of $51.7{\times}10^{-4}W/K^2-m$. The in-plane thermoelectric sensor consisting of 15 pairs of the n-type Bi-Te and the p-type Sb-Te evaporated thin films exhibited a sensitivity of 2.8 mV/K.

• Korean Journal of Materials Research
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• v.14 no.1
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• pp.41-45
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• 2004

P-type $Bi_{0.5}$$Sb_{1.5}$ $Te_3$ thin films were deposited by the flash evaporation technique, and their thermoelectric properties and electronic transport parameters were investigated. The effective mean free path model was adopted to examine the thickness effect on the thermoelectric properties. Annealing effects on the carrier concentration and mobility were also studied, and their variations were analyzed in conjunction with the antisite defects. Seebeck coefficient and electrical resistivity versus inverse thickness showed a linear relationship, and the effective mean free path was found to be 3150$\AA$. No phase transformation and composition change were observed after annealing treatment, but carrier mobility increased due to grain growth. Carrier concentration decreased considerably due to reduction of the antisite defects, so that electrical conductivity decreased and Seebeck coefficient increased. When annealed at 473 K for 1 hr, Seebeck coefficient and electrical conductivity were $160\mu$V/K and 610 $W^{-1}$ $cm^{ -1}$, respectively. Therefore, the thermoelectric quality factor were also enhanced to be $16\mu$W/cm $K^2$.>.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.8
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• pp.961-966
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• 2013

A coupled governing equation of thermoelectric materials can be converted into an uncoupled form to predict the effective Seebeck coefficient of thermoelectric composites, where modified Eshelby model is adopted. The predicted results by the present approach for serial- and parallel-connected composites and composite with spherical inclusions are compared with theoretical and experimental results from literatures to be justified. It is shown that the predictions by the theoretical approaches coincide exactly and show in good agreement with the experiments.

• Journal of the Korean Ceramic Society
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• v.27 no.3
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• pp.412-422
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• 1990

Porous SiC ceramics were proposed to be promising materials for high-temperature thermoelectric energy conversion. Throughthe thermoelectric property measurements and microstructure observations on the porous alpha SiC and the mixture of $\alpha$-and $\beta$-SiC, it was experimentally clarified that elimination of stacking faults and twin boundaries by grain growth is effective to increase the seebeck coefficient and increasing content of $\alpha$-SiC gives rise to lower electrical conductivity. Furthermore, the effects of additives on the thermoelectric properties of 6H-SiC ceramics were also studied. The electrical conductivity and the seebeck coefficient were measured at 35$0^{\circ}C$ to 105$0^{\circ}C$ in argon atmospehre. The thermoelectric conversion efficiency of $\alpha$-SiC ceramics was lower than that of $\beta$-SiC ceramics. The phase homogeneity would be needed to improve the seebeck coefficient and electrical conductivity decreased with increasing the content of $\alpha$-phase. In the case of B addition, XRD analysis showed that the phase transformation did not occur during sintering. On the other hand, AlN addiiton enhanced the reverse phase transformation from 6H-SiC to 4H-SiC, and this phenomenon had a great effect upon the electrical conductivity.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.4
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• pp.611-616
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• 2016

In this study, we synthesized $Ag_2Se$ nanoparticles (NPs) in an aqueous solution and investigated the thermoelectric characteristics of $Ag_2Se$ NPs thin films on plastic substrates. Regardless of thermal annealing treatment, all the $Ag_2Se$ NPs thin films show the negative Seebeck coefficients, indicating the n-type characteristics. As the annealing temperature increases, the electric conductivity increases while the Seebeck coefficient decreases. The electric conductivity of the thin film annealed at $180^{\circ}C$ is larger by $10^6$ times, compared with the as-prepared thin film, And the maximum power density for the thin film annealed at $180^{\circ}C$ is calculated to be $44{\mu}W/cm^2$.

• Korean Journal of Materials Research
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• v.21 no.8
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• pp.456-460
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• 2011

Microelectromechanical systems (MEMS)-fabricated suspended devices were used to measure the in-plane electrical conductivity, Seebeck coefficient, and thermal conductivity of 304 nm and 516 nm thick InGaAlAs films with 0.3% ErAs nanoparticle inclusions by volume. The suspended device allows comprehensive thermoelectric property measurements from a single thin film or nanowire sample. Both thin film samples have identical material compositions and the sole difference is in the sample thickness. The measured Seebeck coefficient, electrical conductivity, and thermal conductivity were all larger in magnitude for the thicker sample. While the relative change in values was dependent on the temperature, the thermal conductivity demonstrated the largest decrease for the thinner sample in the measurement temperature range of 325 K to 425 K. This could be a result of the increased phonon scattering due to the surface defects and included ErAs nanoparticles. Similar to the results from other material systems, the combination of the measured data resulted in higher values of the thermoelectric figure of merit (ZT) for the thinner sample; this result supports the theory that the reduced dimensionality, such as in twodimensional thin films or one-dimensional nanowires, can enhance the thermoelectric figure of merit compared with bulk threedimensional materials. The results strengthen and provide a possible direction in locating and optimizing thermoelectric materials for energy applications.

• Korean Journal of Materials Research
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• v.21 no.10
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• pp.542-545
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• 2011

Half-Heusler alloys are a potential thermoelectric material for use in high-temperature applications. In an attempt to produce half-Heusler thermoelectric materials with fine microstructures, TiCoSb was synthesized by the mechanical alloying of stoichiometric elemental powder compositions and then consolidated by vacuum hot pressing. The phase transformations during the mechanical alloying and hot consolidation process were investigated using XRD and SEM. A single-phase, half- Heusler allow was successfully produced by the mechanical alloying process, but a minor portion of the second phase of the CoSb formation was observed after the vacuum hot pressing. The thermoelectric properties as a function of the temperature were evaluated for the hot-pressed specimens. The Seebeck coefficients in the test range showed negative values, representing n-type conductivity, and the absolute value was found to be relatively low due to the existence of the second phase. It is shown that the electrical conductivity is relatively high and that the thermal conductivities are compatibly low in MA TiCoSb. The maximum ZT value was found to be relatively low in the test temperature range, possibly due to the lower Seebeck coefficient. The Hall mobility value appeared to be quite low, leading to the lower value of Seebeck coefficient. Thus, it is likely that the single phase produced by mechanical alloying process will show much higher ZT values after an excess Ti addition. It is also believed that further property enhancement can be obtained if appropriate dopants are selectively introduced into this MA TiCoSb System.

• Journal of the Korean Ceramic Society
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• v.37 no.7
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• pp.632-637
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• 2000

Thermoelectric conversion properties of commercial Fe-Si2 and Fe-Si alloy ingots prepared by RF inductive furnace were investigated. As sintering temperature increased, density of the specimen increased and the phase transformation from metallic phases ($\varepsilon$-FeSi, ${\alpha}$-Fe2Si5) to semiconducting phase (${\beta}$-FeSi2) occurred more effectively. The FeSi phase was detected even after 100hrs of annealing treatment. For the Fesi1.95∼FeSi2.05 specimens prepared by RF inductive furnace, the thermoelectric property improved as the composition of the specimen approached to stoichiometric composition FeSi2. Electrical conductivity of the specimen increased with increasing temperatures showing typical semiconducting behavior. From the electrical conductivity measurements, activation energy in the intrinsic region (above about 700 K) was calculated to be approximately 0.46 eV. In spite of non-doping, the Seebeck coefficient for every specimen exhibited p-type conduction due to Si deficiency. Its maximum value was located at about 475 K, and then decreased abruptly with increasing temperatures. The power factor was governed by the Seebeck coefficient of the specimen more significantly than by electrical conductivity.

• Korean Journal of Metals and Materials
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• v.50 no.11
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• pp.839-845
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• 2012

The effect of an AlN additive on the thermoelectric properties of SiC ceramics was studied. Porous SiC ceramics with 48-54% relative density were fabricated by sintering the pressed ${\alpha}-SiC$ powder compacts with AlN at $2100-2200^{\circ}C$ for 3 h in an Ar atmosphere. In the undoped specimens, the Seebeck coefficients were positive (p-type semiconducting) possibly due to a dominant effect of the acceptor impurities (Al, Fe) contained in the starting powder. With AlN addition, the reverse phase transformation of 6H-SiC to 4H-SiC was observed during the sintering process. The electrical conductivity of the AlN doped specimen was larger than that of the undoped specimen under the same conditions, which might be due to a reverse phase trans-formation. The Seebeck coefficient of the AlN doped specimen was also larger than that of the undoped specimen. The density of specimen and the amount of addition had significant effects on the thermoelectric properties.

• Electronic Materials Letters
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• v.14 no.6
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• pp.725-732
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• 2018

The thermoelectric and transport properties of Ti-doped FeVSb half-Heusler alloys were studied in this study. $FeV_{1-x}Ti_xSb$ (0.1 < x < 0.5) half-Heusler alloys were synthesized by mechanical alloying process and subsequent vacuum hot pressing. After vacuum hot pressing, a near singe phase with a small fraction of second phase was obtained in this experiment. Investigation of microstructure revealed that both grain and particle sizes were decreased on doping which would influence on thermal conductivity. No foreign elements pick up from the vial was seen during milling process. Thermoelectric properties were investigated as a function of temperature and doping level. The absolute value of Seebeck coefficient showed transition from negative to positive with increasing doping concentrations ($x{\geq}0.3$). Electrical conductivity, Seebeck coefficient and power factor increased with the increasing amount of Ti contents. The lattice thermal conductivity decreased considerably, possibly due to the mass disorder and grain boundary scattering. All of these turned out to increase in power factor significantly. As a result, the thermoelectric figure of merit increased comprehensively with Ti doping for this experiment, resulting in maximum thermoelectric figure of merit for $FeV_{0.7}Ti_{0.3}Sb$ at 658 K.