• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1223-1224
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• 2006

The p-type $(Bi_{0.2}Sb_{0.8})_2Te_3/(Pb_{0.7}Sn_{0.3})$Te functional gradient material (FGM) was fabricated by hot-pressing the mechanically alloyed $(Bi_{0.2}Sb_{0.8})_2Te_3$ and the 0.5 at% $Na_2Te-doped$ $(Pb_{0.7}Sn_{0.3})Te$ powders. Also, the n-type $Bi_2(Te_{0.9}Se_{0.1})_3/PbTe$ FGM was processed by hot-pressing the mechanically alloyed $Bi_2(Te_{0.9}Se_{0.1})_3$ and the 0.3 wt% Bi-doped PbTe powders. With ${\Delta}T$ larger than $300^{\circ}C$, the p-type $(Bi_{0.2}Sb_{0.8})_2Te_3/(Pb_{0.7}Sn_{0.3})Te$ FGM exhibited larger thermoelectric output power than those of the $(Bi_{0.2}Sb_{0.8})_2Te_3$ and the 0.5 at% $Na_2Te-doped$ $(Pb_{0.7}Sn_{0.3})Te$ alloys. For the n-type $Bi_2(Te_{0.9}Se_{0.1})_3/PbTe$ FGM, the thermoelectric output power superior to those of the $Bi_2(Te_{0.9}Se_{0.1})_3$ and the 0.3 wt% Bi-doped PbTe was predicted at ${\Delta}T$ larger than $300^{\circ}C$.

• 한국분말재료학회지
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• 제22권4호
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• pp.254-259
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• 2015

$Bi_2Te_3$ related compounds show the best thermoelectric properties at room temperature. However, n-type $Bi_2Te_{2.7}Se_{0.3}$ showed no improvement on ZT values. To improve the thermolectric propterties of n-type $Bi_2Te_{2.7}Se_{0.3}$, this research has Cu-doped n-type powder. This study focused on effects of Cu-doping method on the thermoelectric properties of n-type materials, and evaluated the comparison between the Cu chemical and mechanical doping. The synthesized powder was manufactured by the spark plasma sintering(SPS). The thermoelectric properties of the sintered body were evaluated by measuring their Seebeck coefficient, electrical resistivity, thermal conductivity, and hall coefficient. An introduction of a small amount of Cu reduced the thermal conductivity and improved the electrical properties with Seebeck coefficient. The authors provided the optimal concentration of $Cu_{0.1}Bi_{1.99}Se_{0.3}Te_{2.7}$. A figure of merit (ZT) value of 1.22 was obtained for $Cu_{0.1}Bi_{1.9}Se_{0.3}Te_{2.7}$ at 373K by Cu chemical doping, which was obviously higher than those of $Cu_{0.1}Bi_{1.9}Se_{0.3}Te_{2.7}$ at 373K by Cu mechanical doping (ZT=0.56) and Cu-free $Bi_2Se_{0.3}Te_{2.7}$ (ZT=0.51).

• 한국결정성장학회지
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• 제25권4호
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• pp.135-139
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• 2015

단결정 ingot 성장기술 중 하나인 traveling heater method(THM) 기술을 이용하여 n형 열전소재인 $Bi_2Te_3-Bi_2Se_3$ 고용체화합물을 성장하였다. 고용체 화합물내 $CdCl_2$와 $SbI_3$을 첨가하여 dopant의 영향을 확인하였고 각각의 dopant의 최적의 첨가량[$CdCl_2$ 0.1 wt%(Z: $2.73{\times}10^{-3}/K$), $SbI_3$ 0.05 wt%(Z: $2.29{\times}10^{-3}/K$)]을 확인하였다. THM 기술을 통해 성장된 ingot의 각 부위별 열전특성을 확인해 본 결과 주요 인자들의 표준편차가 낮은 매우 균질화된 특성을 보였다. 또한 $Bi_2Te_3-Bi_2Se_3$ 고용체화합물의 비등방성 지수와 dopant와의 관계를 확인하기 위하여 $90(Bi_2Te_3)10(Bi_2Se_3)$ 조성의 고용체화합물에 donor dopant로서 $CdCl_2$(0.05~0.1 wt%)을 첨가하여 dopant의 증가에 따른 비등방성 지수의 변화를 확인해본 결과 dopant가 증가함에 따라 비등방성 지수가 변하는 것을 확인하였고 이러한 비등방성 지수의 변화가 실제 열전성능에 크게 영향을 미치는 것을 확인하였다.

• Nuclear Engineering and Technology
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• 제55권8호
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• pp.3080-3087
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• 2023

Thermoelectric (TE) materials working in radioisotope thermoelectric generators are irradiated by neutrons throughout its service; thus, investigating the neutron irradiation stability of TE devices is necessary. Herein, the influence of neutron irradiation with fluences of 4.56 × 10¹⁰ and 1 × 10¹³ n/cm² by pulsed neutron reactor on the electrical and thermal transport properties of n-type Bi₂Te_2.7Se_0.3 and p-type Bi_0.5Sb_1.5Te₃ thermoelectric alloys prepared by cold-pressing and molding is investigated. After neutron irradiation, the properties of thermoelectric materials fluctuate, which is related to the material type and irradiation fluence. Different from p-type thermoelectric materials, neutron irradiation has a positive effect on n-type Bi₂Te_2.7Se_0.3 materials. This result might be due to the increase of carrier mobility and the optimization of electrical conductivity. Afterward, the effects of p-type and n-type TE devices with different treatments on the output performance of TE devices are further discussed. The positive and negative effects caused by irradiation can cancel each other to a certain extent. For TE devices paired with p-type Bi_0.5Sb_1.5Te₃ and n-type Bi₂Te_2.7Se_0.3 thermoelectric legs, the generated power and conversion efficiency are stable after neutron irradiation.

• 한국재료학회지
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• 제7권1호
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• pp.40-49
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• 1997

기계적 합금화 공정과 가압소결법으로 $Bi_{2}(Te_{0.9}Se_{0.1})_{3}$ 열전재료를 제조하여, 가압소결온도 및 dopant첨가에 따른 미세구조와 열전특성의변화를 연구하였다. 평균 3.6mm 크기의 Bi, Te, Se granule을 볼과 원료금속의 무게비 5:1에서 3 시간 기계적 합금화 하므로써 $Bi_{2}(Te_{0.9}Se_{0.1})_{3}$ 합금분말의 형성이 완료되었다. $Bi_{2}(Te_{0.9}Se_{0.1})_{3}$ 가압소결체의 성능지수는 $450^{\circ}C$ 이상의 온도에서 가압소결시 급격히 증가하였으며, $550^{\circ}C$에서 가압소결한 시편에서 $1.9{\times}10^{-3}/K$의 값을 얻었다. $550^{\circ}C$에서 가압소결한 $Bi_{2}(Te_{0.9}Se_{0.1})_{3}$의 성능지수는 acceptor dopant 인 Bi를 0.015wt %첨가함에 따라 $2.1{\times}10^{-3}/K$로 향상되었다.

• 한국분말재료학회지
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• 제18권5호
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• pp.437-442
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• 2011

The present study focused on the synthesis of Bi-Te-Se-based powder by an oxide-reduction process, and analysis of the thermoelectric properties of the synthesized powder. The phase structure, chemical composition, and morphology of the synthesized powder were analyzed by XRD, EPMA and SEM. The synthesized powder was sintered by spark plasma sintering. The thermoelectric properties of the sintered body were evaluated by measuring its Seebeck coefficient, electrical resistivity, and thermal conductivity. $Bi_2Te_{2.7}Se_{0.3}$ powder was synthesized from a mixture of $Bi_2O_3$, $TeO_2$, and $SeO_2$ powders by mechanical milling, calcination, and reduction. The sintered body of the synthesized powder exhibited n-type thermoelectric characteristics. The thermoelectric properties of the sintered bodies depend on the reduction temperature. The Seebeck coefficient and electrical resistivity of the sintered body were increased with increasing reduction temperature. The sintered body of the $Bi_2Te_{2.7}Se_{0.3}$ powder synthesized at $360^{\circ}C$ showed about 0.5 of the figure of merit (ZT) at room temperature.

• 한국재료학회지
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• 제6권7호
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• pp.678-683
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• 1996

In the fabrication processes of thin film thermoelectrics, a subsequent annealing treatment is inevitable to reduce the defects and residual stresses introduced during the film growth, and to make the uniform carrier concentration of the film. However, the diffusion-induced atomic redistribution and the broadening of p/n junction region are expected to affect the thermoelectric properties of thin film modules. The present study intends to investigate the diffusion at the p/n junctions of thermoelectric thin films and to relate it to the property changes. The film junctions of p-type(Bi0.5Sb1.5Te3)and n-type(Bi2Te2.4Se0.6)were prepared by the flash evaporation method. Aluminum thin layer was employed as a diffusion barrier between p-and n-type films of the junction. This was found to be an effective barrier by showing a negligible diffusion into both type films. After annealing treatment, the thermoelectric properties of p/n couples with aluminum barrier layer were accordingly retained their properties without any deterioration.

• 한국분말재료학회지
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• 제23권2호
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• pp.126-131
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• 2016

The recent rise in applications of thermoelectric materials has attracted interest in studies toward the fabrication of thermoelectric materials using mass production techniques. In this study, we successfully fabricate n-type $Bi_2Te_{2.7}Se_{0.3}$ material by a combination of mass production powder metallurgy techniques, gas atomization, and spark plasma sintering. In addition, to examine the effects of hydrogen reduction in the microstructure, the thermoelectric and mechanical properties are measured and analyzed. Here, almost 60% of the oxygen content of the powder are eliminated after hydrogen reduction for 4 h at $360^{\circ}C$. Micrographs of the powder show that the reduced powder had a comparatively clean surface and larger grain sizes than unreduced powder. The density of the consolidated bulk using as-atomized powder and reduced atomized powder exceeds 99%. The thermoelectric power factor of the sample prepared by reduction of powder is 20% better than that of the sample prepared using unreduced powder.

• 열처리공학회지
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• 제31권3호
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• pp.126-134
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• 2018

In this research, we produced polycrystalline n-type $Bi_2Te_{2.7}Se_{0.3}$ powder using water atomization. To obtain full benefit through water atomized powder, we have implemented spark plasma sintering and hot extrusion for powder compaction. The microstructure and thermoelectric properties were investigated and compared. The average grain size of SPS and extruded bulks were 3.08 and $3.86{\mu}m$ respectively. The extruded material microstructure contains layered grains with less grain boundaries and its counter-part SPS displays dense packed grains with high grain boundaries. Among both bulks, extrusion sample exhibited high power factor (PF) of $2.96{\times}10^{-3}Wm^{-1}K^{-2}$ which is 38% higher than SPS ($2.14{\times}10^{-3}$) bulk sample. Due to variations in grain size and grain boundaries, the SPS bulk shows low thermal conductivity than extruded bulk. However, the extruded bulk sample exhibited a peak ZT of 0.69 at 400 K, which is 19% higher than SPS bulk sample, due to its higher power factor.

• 한국재료학회지
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• 제7권5호
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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.