• Journal of the Microelectronics and Packaging Society
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• v.15 no.3
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• pp.1-8
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• 2008

Effects of annealing process in a reduction ambient on thermoelectric properties of the $(Bi,Sb)_{2}Te_3$ thin films prepared by thermal evaporation have been investigated. With annealing at $300^{\circ}C$ for 2 hrs in a reduction ambient(50% $H_2$+50% Ar), the crystallinity of the $(Bi,Sb)_{2}Te_3$ thin films were substantially improved with remarkable increase in the grain size. Seebeck coefficients of the $(Bi,Sb)_{2}Te_3$ thin films increased from$\sim90{\mu}V/K$ to $\sim180{\mu}V/K$ with annealing in the reduction ambient due to decrease in the hole concentration. Power factors of the $(Bi,Sb)_{2}Te_3$ thin films were remarkably improved for $5\sim16$ times with annealing in the reduction atmosphere. After annealing in the reduction ambient, a $(Bi,Sb)_{2}Te_3$ evaporated film exhibited a maximum power factor of $18.6\times10^{-4}W/K^{2}-m$.

• Journal of the Microelectronics and Packaging Society
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• v.7 no.4
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• pp.1-5
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• 2000

Properties of AC applied hot pressed ($Pb_{1-x}Sn_{x}$) Te thermoelectrics were investigated. Mechanical alloying process used to produce alloyed powder to reduce the inhomogeneity and to avoid vaporization of constituents. It showed an increase in the mechanical alloying time with increasing of Sn contents in ($Pb_{1-x}Sn_{x}$)Te. ($Pb_{1-x}Sn_{x}$)Te were sintered at 873 to 923K for 1-4 minutes, under 150 kgf/$\textrm{cm}^2$ by AC applied hot pressng method. The short sintering time of AC applied hot pressing process could reduce the vaporization of Te. The density of ($Pb_{1-x}Sn_{x}$) Te was more dependent on the sintering temperature than the sintering time. The p-n transition was observed at x=0.1 but only p type conduction behavior was observed at more than 20 mol% of Sn compositions. The maximum value of Seebeck coefficient is 250 $\mu$V/K for x=0.2 at 500K. As the amount of Sn increases, the peak value of Seebeck coefficient drops and shifts to higher temperature and the peak value of electrical conductivity decreased with increasing temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.6
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• pp.502-507
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• 2010

In order to design nano structured materials with enhanced thermoelectric properties, the alloys in the pseudo-binary $Bi_2Te_3$-PbTe system are investigated for their micro structure properties. For this synthesis, the liquid alloys are cooled by the water quenching method. Micro structure images are obtained by using an electron probe micro analyzer(EPMA). Dendritic and lamellar structures are clearly observed with the variation in the composition ratio between $Bi_2Te_3$ and PbTe. The increase in the $Bi_2Te_3$ composition ratio causes to change of the structure from dendritic to lamellar. The Seebeck coefficient of sample 5, in which the mixture rate of $Bi_2Te_3$ is 83%, is measured as the highest value. In contrast, the others decrease with the increase of the $Bi_2Te_3$ composition ratio. Meanwhile, p-type characteristics are observed in sample 6, at 91%-$Bi_2Te_3$ mixture rate. The power factors of the all samples are calculated with the Seebeck coefficient and resistivity.

• Korean Journal of Materials Research
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• v.13 no.5
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• pp.292-296
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• 2003

In an attempt to enhance phase transformation and homogenization of Mn-doped $FeSi_2$, mechanical alloying of elemental powders was applied. Cold pressing and sintering in vacuum were carried out to produce a dense microstructure, and then isothermal annealing was employed to induce a phase transformation to the $\beta$-$FeSi_2$semiconductor. Phase transitions in this alloy system during the process were investigated by using XRD, EDS and SEM. As-milled powders after 100 h of milling were shown to be metastable state. As-sintered iron silicides consisted of untransformed mixture of $\alpha$-$Fe_2$$Si_{5}$and $\varepsilon$-FeSi phases. $\beta$-$FeSi_2$phase transformation was induced by subsequent isothermal annealing at $830^{\circ}C$, and near single phase of $\beta$-$FeSi_2$was obtained after 24 h of annealing. Thermoelectric properties in terms of Seebeck coefficient, and electrical conductivity were evaluated and correlated with phase transformation. Seebeck coefficient electrical resistivity and hardness increased with increasing annealing time due to $\beta$ phase transformation.

• Korean Journal of Materials Research
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• v.21 no.4
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• pp.192-195
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• 2011

The electro-deposition of compound semiconductors has been attracting more attention because of its ability to rapidly deposit nanostructured materials and thin films with controlled morphology, dimensions, and crystallinity in a costeffective manner (1). In particular, low band-gap $A_2B_3$-type chalcogenides, such as $Sb_2Te_3$ and $Bi_2Te_3$, have been extensively studied because of their potential applications in thermoelectric power generator and cooler and phase change memory. Thermoelectric $Sb_xTe_y$ films were potentiostatically electrodeposited in aqueous nitric acid electrolyte solutions containing different ratios of $TeO_2$ to $Sb_2O_3$. The stoichiometric $Sb_xTe_y$ films were obtained at an applied voltage of -0.15V vs. SCE using a solution consisting of 2.4 mM $TeO_2$, 0.8 mM $Sb_2O_3$, 33 mM tartaric acid, and 1M $HNO_3$. The stoichiometric $Sb_xTe_y$ films had the rhombohedral structure with a preferred orientation along the [015] direction. The films featured hole concentration and mobility of $5.8{\times}10^{18}/cm^3$ and $54.8\;cm^2/V{\cdot}s$, respectively. More negative applied potential yielded more Sb content in the deposited $Sb_xTe_y$ films. In addition, the hole concentration and mobility decreased with more negative deposition potential and finally showed insulating property, possibly due to more defect formation. The Seebeck coefficient of as-deposited $Sb_2Te_3$ thin film deposited at -0.15V vs. SCE at room temperature was approximately 118 ${\mu}V/K$ at room temperature, which is similar to bulk counterparts.

• Korean Journal of Materials Research
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• v.15 no.2
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• pp.89-92
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• 2005

The induction melting was employed to prepare Nb-doped $CoSb_3$ skutterudites and their thermoelectric properties were investigated. Single phase $\delta-CoSb_3$ was successfully obtained by induction melting and subsequent annealing at $400^{\circ}C$ for 2 hrs in vacuum. The positive signs of Seebeck coefficients for all the specimens revealed that Nb atoms acted as p-type dopants by substituting Co atoms. Electrical conductivity decreased and then increased with increasing temperature, indicating mixed conduction behavior. Electrical conductivity increased by Nb doping, and it was saturated at high temperature. Maximum value of the thermoelectric power factor was shifted to higher temperature with increasing the amount of Nb doping, mainly originated from the high Seebeck coefficient around mixed conduction temperature and high electrical conductivity.

• Composites Research
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• v.29 no.4
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• pp.156-160
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• 2016

Glassy carbon can be utilized in a variety of harsh environment due to exceptional thermal stability and chemically impermeability along with scalability and low electrical resistance. In this work, we studied effects of electron(e)-beam irradiation on thermoelectric properties of the glassy carbon film. E-beam irradiation triggered local crystallization and/or amorphization of glassy carbon thin films, which was determined by a Raman spectroscopy. The structural change by e-beam irradiation leads to the change in the doping level of the glassy carbon, which can be inferred from the change of a Seebeck coefficient and an electric conductivity. The optimal power factor we obtained for the irradiated glassy carbon film was ~200% higher than that of the non-irradiated sample.

• Journal of Energy Engineering
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• v.25 no.4
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• pp.133-140
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• 2016

Thermoelectric generator, which is known as using Seebeck effect, have been widely applied in many industrial parts, for instance, from submarine to equipments capable of producing hot or cooling water. Its usefulness was verified in terms of producing electric power using temperature difference and vice versa. Application on thermoelectric generator has been mainly forced on exhaust gas of automotive engine so far. In this study, the possibility was investigated whether electric power could be produced by using cooling water in automotive engine. As the result, it showed that electric power had differences depending on shapes of power auxiliary apparatus and, in this experiment, maximum of electric power was 1.5 voltage.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.04b
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• pp.7-7
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• 2009

Lead telluride (PbTe) is a very promising thermoelectric material due to its narrow band gap (0.31 eV at 300 K), face-centered cubic structure and large average excitonic Bohr radius (46 nm) allowing for strong quantum confinement within a large range of size. In this work, we present the thermoelectric properties of individual single-crystalline PbTe nanowires grown by a vapor transport method. A combination of electron beam lithography and a lift-off process was utilized to fabricate inner micron-scaled Cr (5 nm)/Au (130 nm) electrodes of Rn (resistance of a near electrode), Rf (resistance of a far electrode) and a microheater connecting a PbTe nanowire on the grid of points. A plasma etching system was used to remove an oxide layer from the outer surface of the nanowires before the deposition of inner electrodes. The carrier concentration of the nanowire was estimated to be as high as $3.5{\times}10^{19}\;cm^{-3}$. The Seebeck coefficient of an individual PbTe nanowire with a radius of 68 nm was measured to be $S=-72{\mu}V/K$ at room temperature, which is about three times that of bulk PbTe at the same carrier concentration. Our results suggest that PbTe nanowires can be used for high-efficiency thermoelectric devices.

• Korean Journal of Materials Research
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• v.8 no.3
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• pp.245-251
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• 1998

Bi-doped n-type PbTe thermoeletric materials were fabricated by mechanical alloying and hot pressing. The intering characteristics and thermoelectric properties of the hot- pressed PbTe were characterized and compared with the properties of the specimens prepared by meltingigrinding method. The hot-pressed PbTe specimens fabricated by mechanical alloying exhibited more negative Seebeck coefficient, higher electrical resistivity and lower thermal conductivity. compared to ones prepared by meltingigrinding. The maximum figure-of-merit increased and the temperature for the maximum figure-of-merit shifted to lower temperature for the specimens fabricated by mechanical alloying. When hot pressed at $650^{\circ}C$, 0.3 wt% Bi-doped PbTe fabricated by mechanical alloying and meltingjgrinding exhibited maximum figure-of-merits of $1.33\times10^{-3}/K$ at $200^{\circ}C$ and $1.07\times10^{-3}/K$ at $400^{\circ}C$ respectively.