• Title/Summary/Keyword: thermoelectric properties

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Synthesis and Characterization of Delafossite $CuLaO_2$ for Thermoelectric Application

  • Takahashi, Yuhsuke;Matsushita, Hiroaki;Katsui, Akinori
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09b
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    • pp.1114-1115
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    • 2006
  • The preparation of single-phase $CuLaO_2$ with delafossite-type structure by means of the solid-state reaction method was investigated using X-ray diffraction. The results showed that notwhistanding the fact that there was a trace of metallic copper, nearly single-phase $CuLaO_2$ was obtained by using $La(OH)_3$ as a lanthanum source and by firing the mixed powder with nonstoichiometric composition ratio of $La(OH)_3:Cu_2O=1:1.425$ in a vacuum at 1273 K for 10 h. The measurement of electrical conductivity and Seebeck coefficient showed that $CuLaO_2$ thus obtained was a p-type semiconductor and had a Seebeck coefficient of approximately $70{\mu}V/K$.

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Electrical Properties of Poly (1,4-phenylene vinylene-co-2,5-dimethoxy-1,4-phenylene vinylene)s and Poly(1,4-phenylene vinylene-co-2,5-thienylene vinylene)s

  • Hong-Ku Shim;Sae-Kyung Kim;Jung-Il Jin;Kil-Ho Kim;Yung-Woo Park
    • Bulletin of the Korean Chemical Society
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    • v.11 no.1
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    • pp.11-15
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    • 1990
  • The temperature dependence of electrical conductivities and thermoelectric power of $I_2$-doped poly(1,4-penylene vinylene-co-2,5-dimethoxy-1,4-phenylene vinylene)s [poly(PV-co-DMPV)] and poly(1,4-phenylene vinylene-co-2,5-thienylene vinylene)s [poly(PV-co-TV)] were studied. The former copolymers were also doped with $FeCl_3$. All the samples used were in thin film forms. The temperature dependence of electrical conductivity implies that the variable range hopping conduction mechanism applises to these systems. The activation energy for the electrical conduction in dimethoxy-phenylene vinylene (DMPV) copolymers ranged from about 7 to 30 meV depending on the polymer composition and the nature of the dopant. It was significantly higher for $I_2$-doped thienylene vinylene (TV) copolymers, namely 90-200 meV. The values of the room temperature thermoelectric power were $30-70{\mu}V/K$ for DMPV copolymer and $100-800{\mu}V/K$ for TV copolymers. Anisotropy in the electrical conductivities was also studied for oriented films obtained by uniaxial stretching of the precursor polymer films.

The synthesis and properties of point defect structure of Cu2-XZnSnS4 (x=0.1, 0.2, and 0.3)

  • Bui D. Long;Le T. Bang
    • Advances in materials Research
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    • v.13 no.1
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    • pp.55-62
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    • 2024
  • Cu-based sulfides have recently emerged as promising thermoelectric (TE) materials due to their low cost, non-toxicity, and abundance. In this research, point defect structure of Cu2-xZnSnS4 (x=0.1, 0.2, 0.3) samples were synthesized by the mechanical alloying method. Mixed powders of Cu, Zn, Sn and S were milled using high energy ball milling at a rotation speed of 300 rpm in Ar atmosphere. The milled Cu2-xZnSnS4 powders were heat-treated at 723 K for 24 h, and subsequently consolidated using spark plasma sintering (SPS) under an applied pressure of 60 MPa for 15 min. The thermal conductivity of the sintered Cu2-xZnSnS4 samples was evaluated. A well-defined Cu2-xZnSnS4 powders were successfully formed after milling for 16 h, with the particle sizes mostly distributed in the range of 60-100 nm. The lattice constants of aand cdecreased with increasing composition value x. The thermal conductivity of sintered x=0.1 sample exhibited the lowest value and attained 0.93 W/m K at 673 K.

Chemical Analysis and Thermoelectric Properties of the PbSnTe Semiconductors (화학조성에 따른 PbSnTe계 반도체의 열전특성조사)

  • Oh, Kyu-Whan;Oh, Seung-Mo
    • Applied Chemistry for Engineering
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    • v.1 no.1
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    • pp.83-90
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    • 1990
  • The semiconducting $(Pb_1\;_xSn_x)_1$ $_yTe_y$, one of the low - temperature thermoelectric materials, has been prepared and its chemical composition and nonstoichiometry has been analyzed. The content of Pb in the specimens was determined by the complexometric back - titration method with EDTA and Pb(II) standard solutions. Te - content was analyzed with the redox titration method. The electrical conductivity and the thermoelectric power have also been measured by the DC 4 - probe and the heat-pulse technique, respectively. All of the specimens showed a nonstoichiometric behavior in their chemical compositions (Te excess), thus gave rise to a p - type semiconducting property, and the nonstoichoimetry became bigger as the Sn - content increased. The thermoelectric power vs. temperature results have been analyzed upon the basis of the Fermi level vs. temperature profiles in the saturation regime. The specimen of x=0.1 evolved a transition from p - to n - type property at about 670K, which has been explained by the fact that the mobility of electrons is bigger than that of holes in the temperature range of the intrinsic regime.

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Thermoelectric Properties of Bi-Te Thin Films Processed by Coevaporation (동시증착법으로 형성한 Bi-Te 박막의 열전특성)

  • Choi, Young-Nam;Kim, Min-Young;Oh, Tae-Sung
    • Journal of the Microelectronics and Packaging Society
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    • v.17 no.4
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    • pp.89-94
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    • 2010
  • Bi-Te films were processed by coevaporation of Bi and Te dual sources with variations of the mole ratio of the Bi and Te evaporation sources, and thermoelectric properties of the coevaporated Bi-Te films were characterized. The coevaporated Bi-Te films were n-type semiconductors and exhibited Seebeck coefficients of $-60{\sim}-80{\mu}V/K$. The Terich Bi-Te film, processed with Bi and Te dual sources of 30 mol% Bi : 70 mol% Te ratio, exhibited a power factor of $5{\times}10^{-4}W/m-K^2$. On the other hand, a power factor of $17.7{\times}10^{-4}W/m-K^2$ was obtained for the Bi-rich film coevaporated using Bi and Te dual sources of 90 mol% Bi : 10 mol% Te ratio.

Effects of Various Fabrication Routes on Thermoelectric Properties of n-type Bi2Te2.85Se0.15 Alloys (제조공정에 따른 n형 Bi2Te2.85Se0.15합금의 열전성능 평가)

  • Nagarjuna, C.;Shin, D.W.;Lee, M.W.;Lee, S.H.;Hong, S.J.
    • Journal of the Korean Society for Heat Treatment
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    • v.31 no.3
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    • pp.135-142
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    • 2018
  • In this study, we have fabricated n-type $Bi_2Te_{2.85}Se_{0.15}$ compounds by different processing routes such as crushing, milling and mixing respectively. Subsequently, the obtained powders were consolidated by spark plasma sintering (SPS). The phase crystallinity of bulk samples were identified using X-ray diffraction technique. Powder morphology and fracture surface of bulk samples were observed using the scanning electron microscopy (SEM). The Seebeck coefficient and electrical conductivity values were significantly increased for the milling sample than crushing and mixing samples. As a result, the maximum power factor was obtained $2.4mW/mK^2$, which is thrice than that of crushing process. The maximum figure of merit (ZT) of 0.77 was achieved at 400 K for the milling sample. Furthermore, relatively high hardness and density values were noticed for the different processed samples.

Comparative Studies of Different Thermal Consolidation Techniques on Thermoelectric Properties of BiTeSe Alloy (BiTeSe 합금의 열적성형방법에 따른 열전특성)

  • Sharief, P.;Dharmaiah, P.;Lee, C.H.;Ahn, S.S.;Lee, S.H;Son, H.T;Hong, S.J.
    • Journal of the Korean Society for Heat Treatment
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    • v.31 no.3
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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.

Thermoelectric Properties of n-Type Half-Heusler Compounds Synthesized by the Induction Melting Method

  • Du, Nguyen Van;Lee, Soonil;Seo, Won-Seon;Dat, Nguyen Minh;Meang, Eun-Ji;Lim, Chang-Hyun;Rahman, Jamil Ur;Kim, Myong Ho
    • Transactions on Electrical and Electronic Materials
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    • v.16 no.6
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    • pp.342-345
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    • 2015
  • The n -type Hf0.25Zr0.25Ti0.5NiSn0.998Sb0.002 Half-Heusler (HH) alloy composition was prepared by using the induction melting method in addition to the mechanical grinding, annealing, and spark plasma sintering processes. Analysis of X-ray diffraction (XRD) results indicated the formation of a pure phase HH structured compound. The electrical and thermal properties at temperatures ranging from room temperature to 718 K were investigated. The electrical conductivity increased with increasing temperatures and demonstrated nondegenerate semiconducting behavior, and a large reduction in the thermal conductivity to the value of 2.5 W/mK at room temperature was observed. With the power factor and thermal conductivity, the dimensionless figure of merit was increased with temperature and measured at 0.94 at 718 K for the compound synthesized by the induction melting process.

Efface of Annealing in a Reduction Ambient on Thermoelectric Properties of the $(Bi,Sb)_{2}Te_{3}$ Thin Films Processed by Vacuum Evaporation (환원분위기 열처리가 $(Bi,Sb)_{2}Te_{3}$ 증착박막의 열전특성에 미치는 영향)

  • Kim, Min-Young;Oh, Tae-Sung
    • 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 $18.6\times10^{-4}W/K^{2}-m$.

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Preparation and Thermal Properties of Aliphatic Network Polyester-Silica Composites (지방족 가교 폴리에스테르-실리카 복합재료의 제조 및 열적특성)

  • Oh, Chang-Jin;Park, Su-Dong;Han, Dong-Cheul;Kwak, Gi-Seop
    • Polymer(Korea)
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    • v.34 no.5
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    • pp.424-429
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    • 2010
  • The hybrid composites of aliphatic polyester-silica were prepared via a sol-gel reaction and their potential application using as a buffer coating layer in the thermoelectric device were investigated. When aliphatic polyesters were thermally treated at a high temperature of $240^{\circ}C$, the polymer showed an increases in thermal degradation temperature by $30{\sim}90^{\circ}C$ according to the thermal treatment time. The polyester-silica composites showed an increases in thermal degradation temperature by $30{\sim}50^{\circ}C$ according to the content of the added silica. Polyester-silica composite showed neither discoloration nor change in optical properties because Knoevenagel condensation reaction was hindered by silica structure. The thermal conductivity of the composites increased linearly according to the content of added silica.