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기계적 합금화 공정으로 제조한 p형 (Bi0.25 Sb0.75)2 Te3 의 열전특성
현도빈,심재동,정부양,오태성,남등의 대한금속재료학회(대한금속학회) 1997 대한금속·재료학회지 Vol.35 No.1
Formation of (Bi_(0. 25)Sb_(0. 75))₂Te₃ alloy was completed by mechanical alloying of the as-mixed Bi, Sb, and Te granules of ∼5 ㎜ size for 5 hours at ball-to-material ration of 5:1. When hot pressed at temperatures ranged from 300℃ to 550℃ for 30 minutes, figure of merit of (Bi_(0. 25)Sb_(0. 75))₂Te₃ increased with increasing hot pressing temperature and maximum value of 2.8×10^(-3)/K could be obtained by hot pressing at 550℃. When hot pressed at 400℃, figure of merit was increased from 2.0×10^(-3)/K to 2.37×10^(-3)/K with addition of 1.25 wt% Sb as an acceptor dopant. With further addition of Sb, however, figure of merit was abruptly decreased. When hot pressed at 550℃, figure of merit(∼2.8×10^(-3)/K) was little changed with addition of Sb up to 2 wt%, and then decreased abruptly below 0.5×10^(-3)/K with further addition of Sb.
기계적 합금화 공정으로 제조한 n 형 PbTe 가압소결체의 소결특성과 열전특성
현도빈,오태성,최재식 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.4
Bi-doped n-type PbTe thermoelectric materials were fabricated by mechanical alloying and hat pressing, and the sintering characteristics and thermoelectric properties of the hot-pressed PbTe were characterized. Even without Bi doping, the hot-pressed PbTe exhibited a negative Seebeck coefficient and thus n-type conduction. With increasing the hot pressing temperature from 650℃ to 800℃, the temperature at which a maximum figure-of-merit was obtained shifted to higher temperature. When hot pressed at 650℃, 0.3 wt% Bi-doped PbTe exhibited a maximum figure-of-merit of 1.33×10³/K at 200℃ With hot pressing at 750℃ and 800℃, 0.1 wt% Bi-doped PbTe exhibited maximum figure-of-merits of 1.27×10^(-3)/K at 250℃ and 1.3×10^(-3)/K at 400℃ respectively.
(100-x)%Bi2Te3-x%Sb2Te3(x≥66.7) 단결정의 전기적 특성과 열전특성
현도빈,심재동,오태성,하헌필,한동균 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.11
Electrical and thermoelectric properties of the undoped (100-x)% Bi₂Te₃-x% Sb₂Te₃ (x≥66.7) pseudo-binary single crystals grown by the zone melting method were measured over the temperature range from 77 to 600K. For the (100-x)% Bi₂Te₃-x% Sb₂Te₃ (x≥66.7) alloys, the temperature dependence of the Hall mobility was T^(-1.0) regardless the Sb₂Te₃ contents. The temperature dependences of (m^*/m_o)^(3/2)·μ_c and the effective mass were proportional to T^(-1.5) and T^(-1/3), respectively. The saturated hole concentration decreased with increasing temperature and the slope of the Seebeck coefficient changed at about 350K, which implied the two sub-bands in the valence band. While the 33.3% Bi₂Te₃-66.7% Sb₂Te₃ alloy exhibited the highest figure-of-merit among the undoped Bi₂Te₃-Sb₂Te₃ alloys, the maximum figure-of-merit could be expected fur the 22.5% Bi₂Te₃-77.5% Sb₂Te₃ alloy with optimizing the carrier concentration.
0.2wt% SbI3 첨가 90% Bi2Te3-(10-x)% Sb2Te3-x% Sb2Se3 고용체 합금의 전기적특성 및 열전특성
현도빈,황종승,심재동,오태성,Barabash, V . A . 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.8
Electrical and thermoelectric properties of the 0.2 wt% SbI₃- doped n-type 90% Bi₂Te₃-(10-x)% Sb₂Te₃-x% Sb₂Se₃ single crystals have been investigated at temperatures ranging from 77K to 600K. The carrier concentration and Seebeck coefficient were independent of the Sb₂Se₃ content. With increasing the Sb₂Se₃ content, the electrical resistivity increased and Hall mobility decreased, which was attributed to the lattice distortion. The thermal conductivity decreased with increasing Sb₂Se₃ content, which was mainly due to the decrease of the electronic thermal conductivity. With increasing the Sb₂Se₃ content, the maximum figure-of-merit decreased and was shifted to the lower temperature. The 0.2 wt% SbI₃-doped 90% Bi₂Te₃-5% Sb₂Te₃-5% Sb₂Se₃ single crystal showed the maximum figure-of-merit of 1.65×10^(-3)/K at 280K.
SbI3 를 첨가한 33.3 % Bi2Te3-66.7 % Sb2Te3 열전반도체의 전기적특성과 열전특성
현도빈,황종승,심재동,오태성,황창원 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.2
The temperature dependences of the electrical and thermoelectric properties of the SbI₃-doped 33.3% Bi₂Te₃66.7% Sb₂Te₃ single crystals have been measured at temperatures ranging from 77K to 600K. The scattering parameter of the 33.3 Bi₂Te₃-66.7% Sb₂Te₃ single crystals was determined as s = 0. With increasing the amount of SbI₃ dopant, the hole concentration of the 33.3% Bi₂Te₃-66,7% Sb₂Te₃ single crystal is decreased, resulting in the increment of the Seebeck coefficient and electrical resistivity, and the temperature for the maximum figure-of-merit shifted to lower temperature. A maximum figure-of-merit of 2.3×10^(-3)/K was obtained for 0.3 wt% SbI₃-doped specimen. It has been revealed that. the addition of SbI₃ as a donor dopant is useful in controlling the hole concentration of p-type 33.3% Bi₂Te₃ 66.7% Sb₂Te₃ alloy system.
가압소결법으로 제조된 p형 Bi2Te3-Sb2-Te3-Sb2Se3 의 삼원계 합금의 열전특성
현도빈,오태성,이준수,김항종 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.5
P-type 20% Bi₂Te₃-(80-x)% Sb₂Te₃-x% Sb₂Se₃ (0≤x≤7) alloy powders, fabricated by mechanical alloying and melting/grinding processes, were hot pressed and their thermoelectric properties were characterized with the Sb₂Se₃ content and the powder processing method. The Seebeck coefficient and electrical resistivity of the hot-pressed 20% Bi₂Te₃-(80-x)% Sb₂Te₃-x% Sb₂Se₃ alloys increased with increasing the Sb₂Se₃ content due to the reduction of the hole concentration. Although the total thermal conductivity of the hot-pressed 20% Bi₂Te₃-(80-x)% Sb₂Te₃-x% Sb₂Se₃ alloys decreased with increasing the Sb₂Se₃ content due to the reduction of κ_(el), the lattice thermal conductivity κ_(ph) was not lowered. The figure-of-merit of the hot-pressed 20% Bi₂Te₃-(80-x)% Sb₂Te₃-x% Sb₂Se₃ alloys decreased with increasing the Sb₂Se₃ content, because the increment of the electrical resistivity was much larger than the decrement of the thermal conductivity and the increment of the Seebeck coefficient.
Sbi3 를 첨가한 25% Bi2Te3-75% Sb2Te3 와 15% Bi2Te3-85% Sb2Te3 단결정의 전기적특성과 열전특성
현도빈,황종승,심재동,오태성,하헌필 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.8
The temperature dependences of the electrical and thermoelectric properties of the SbI₃-doped 25% Bi₂Te₃-75% Sb₂Te₃ and 15% Bi₂Te₃-85% Sb₂Te₃ single crystals, grown by the Bridgman method, were measured at temperatures ranging from 77 K to 600 K. For the Sb₂Te₃-rich single crystals, the temperature dependence of the Hall mobility was T^(-1.0) regardless the Sb₂Te₃ contents and added amount of SbI₃. The temperature dependences of (m*/m_o)^(3/2)·μ_c and effective mass m*/m_o were T^(-1.5) and T^(-1/3), respectively. The decrease of the saturated hole concentration and the change of the slope of the Seebeck coefficient with temperature were considered in the view point of the two sub-bands in the valence band. The maximum figure-of-merit at 300 K of 0.2 wt% SbI₃-doped 25% Bi₂Te₃-75% Sb₂Te₃ and 0.4 wt% SbI₃-doped 15% Bi₂Te₃-85% Sb₂Te₃ single crystals were 2.25×10^(-3)/K and 1.95×10^(-3)/K, respectively.
Zone melting 법으로 성장시킨 90 % Bi2Te3-10 % Bi2Se3 n 형 단결정에서 길이방향에 따른 열전특성의 변화
현도빈,하헌필 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.3
CdI₂ and CdCl₂ doped n-type 90% Bi₂Te₃ 10% Bi₂Se₃ single crystals were grown by the vertical zone melting method, and the thermoelectric properties along the ingot were analyzed. The sharp increase of the Seebeck coefficient and electrical resistivity at the last-to-freeze region were considered as a result of the evaporation of I and Cl from the molten zone. The maximum Figure-of-Merit of the CdI₂ and CdCl₂ doped n-type 90% Bi₂Te₃ 10% Bi₂Se₃ single crystals were 2.7×10^(-3)/K and 2.8×10^(-3)/K, respectively. The higher Figure-of-Merit for the CdCl₂ doped specimens was mainly due to the lower (κ-κ_(el)). The optimum doping amount of CdI₂ and CdCl₂ for n-type 90% Bi₂Te₃-10% Bi₂Se₃ single crystals, grown by the vertical zone melting method, were 0.075-0.10 wt% and 0.04-0.05 wt%, respectively.
SbI3 및 과잉 Te 첨기에 따른 n 형 (Bi2Te3)0.9(Sb2Te3)0.05(Sb2Se3)0.05 가압소결체의 열전특성
현도빈,오태성,이준수,황창원 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.5
Thermoelectric properties of the n-type (Bi₂Te₃)_(0.9)(Sb₂Te₃)_(0.05)(Sb₂Se₃)_(0.05) alloy prepared by melting/grinding and hot pressing, were investigated with variation of the doping amount of SbI₃and excess Te. With increasing the doping amount of SbI₃ and excess Te, the Seebeck coefficient and electrical resistivity of the hot-pressed (Bi₂Te₃)_(0.9)(Sb₂Te₃)_(0.05)(Sb₂Te₃)_(0.05) alloy were lowered due to the increase in the electron concentration. When SbI₃ and excess Te were doped within 0.1 wt%, SbI₃ exhibited doping effect, i.e., increase in the electron concentration, 2.8 times larger than that of excess Te. The hot-pressed (Bi₂Te3)_(0.9)(Sb₂Te3)_(0.05)(Sb₂Se₃)_(0.05) alloy exhibited maximum figure-of-merits of 2.02×10^(-3)/K and 2.22×10^(-3)/K with doping of 0.025 wt% SbI₃ and 0.2 wt% excess Te, respectively.
P 형 (Bi1-xSbx)2 Te3 열전재료의 기계적 합금화 공정화 열전특성
현도빈,오태성,김항종,정부양 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.3
Thermoelectric properties of p-type polycrystalline (Bi_(1-x)Sb_x)₂Te₃ (0.75 ≤ x ≤ 0.85), fabricated by mechanical alloying and hot pressing, were investigated as a function of the Sb₂Te₃ content and the amount of excess Te addition. The effect of a reduction treatment in Hz atmosphere on thermoelectric properties of (Bi_(1-x)Sb_x)₂Te₃ was also studied. Among (Bi_(1-x)Sb_x)₂Te₃ fabricated by mechanical alloying. (Bi_(0.2)Sb_(0.8))₂Te₃ exhibited the highest figure-of-merit of 2.98×10³/K. When (Bi_(1-x)Sb_x)₂Te₃ powders were reduction-treated in H₂ atmosphere, the Seebeck coefficient and electrical resistivity decreased due to the removal of the oxide layer on the powder surface. With the reduction treatment, the figure-of-merits of (Bi_(0.25)Sb_(0.75))₂Te₃ (Bi_(0.2)Sb_(0.8))₂Te₃, (Bi_(0.15)Sb_(0.85))₂Te₃ were changed from 2.76×10^(-3)/K to 2.79×10^(-3)/K, from 2.98×10^(-3)/K to 2.80×10^-3/K, and from 2.78×10^(-3)/K to 1.81×10^(-3)/K, respectively. When 1.0 wt% excess Te-doped (Bi_(0.2)Sb_(0.8))₂Te₃ powders were reduction-treated, a Figure-of-merit of 3.33×10^(-3)/K was obtained.