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Thermoelectric Characteristics of the p-type (Bi,Sb)2Te3 Nano-Bulk Hot-Pressed with Addition of ZrO2 as Nano Inclusions (ZrO2를 나노개재물로 첨가한 p형 (Bi,Sb)2Te3 나노벌크 가압소결체의 열전특성)

  • Yeo, Y.H.;Kim, M.Y.;Oh, T.S.
    • Journal of the Microelectronics and Packaging Society
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    • v.17 no.3
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    • pp.51-57
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    • 2010
  • Thermoelectric properties of the p-type (Bi,Sb)2Te3, hot-pressed with the (Bi,Sb)2Te3 powders fabricated by melting/grinding method, were characterized with variation of the hot-pressing conditions. Thermoelectric characteristics of the hot-pressed (Bi,Sb)2Te3 were also analyzed with addition of ZrO2 as nano inclusions. With increasing the hotpressing temperature from 350C to 550C, Seebeck coefficient and electrical resistivity decreased from 275 μV/K to 230 μV/K and 6.68 mΩ-cm to 1.86 mΩ-cm, respectively. The power factor decreased with addition of ZrO2 nano powders more than 1 vol%, implying that the optimum amount of ZrO2 nano inclusions to get a maximum power factor would be less than 1 vol%.

Cubic ZrO2 Single Crystals Growth by Skull Method : Effect of Melt Homogenization in Crystallization (스컬(Skull)법에 의한 큐빅 ZrO2단결정 성장 : 융액의 균질화가 결정성장에 미치는 영향)

  • 정대식;오근호
    • Journal of the Korean Ceramic Society
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    • v.27 no.5
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    • pp.597-604
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    • 1990
  • In Cubic ZrO2 crystal growth by Skull method, it was examined on effect of homonization on melt as keeping ZrO2(90mol%)-Y2O3(10mol%) melt with 1hr, 2hr, 4hrs, 8hrs, 16hrs, respectively. The optimum homonizing condition in this system was obtained by the examination between quality of grown crystals and soaking time of melt. It was obtained that the lower quality crystal could be produced in the longer holding melt than the optimum soaking time of melt in spite of the supposedly well homonized state, because the melt stability is sensibly dependent on the convective state of melt in skull method (cold crucible process).

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A comparative study on the flux pinning properties of Zr-doped YBCO film with those of Sn-doped one prepared by metal-organic deposition

  • Choi, S.M.;Shin, G.M.;Joo, Y.S.;Yoo, S.I.
    • Progress in Superconductivity and Cryogenics
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    • v.15 no.4
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    • pp.15-20
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    • 2013
  • We investigated the flux pinning properties of both 10 mol% Zr-and Sn-doped YBa2Cu3O7δ (YBCO) films with the same thickness of ~350 nm for a comparative purpose. The films were prepared on the SrTiO3 (STO) single crystal substrate by the metal-organic deposition (MOD) process. Compared with Sn-doped YBCO film, Zr-doped one exhibited a significant enhancement in the critical current density (Jc) and pinning force density (Fp). The anisotropic Jc,min/Jc,max ratio in the field-angle dependence of Jc at 77 K for 1 T was also improved from 0.23 for Sn-doped YBCO to 0.39 for Zr-doped YBCO. Thus, the highest magnetic Jc values of 9.0 and 2.9MA/cm2 with the maximum Fp (Fp,max) values of 19 and 5GN/m3 at 65 and 77 K for H // c, respectively, could be achieved from Zr-doped YBCO film. The stronger pinning effect in Zr-doped YBCO film is attributable to smaller BaZrO3 (BZO) nanoparticles (the average size 28.4 nm) than YBa2SnO5.5 (YBSO) nanoparticles (the average size 45.0 nm) incorporated in Sn-doped YBCO film since smaller nanoparticles can generate more defects acting as effective flux pinning sites due to larger incoherent interfacial area for the same doping concentration.

Effects of A-site Ca and B-site Zr Substitution on the Dielectric Characteristics and Microstructure of BaTiO3-CaTiO3 Composite (A-site Ca 및 B-site Zr 첨가에 의한 BaTiO3-CaTiO3복합체의 유전특성 및 미세구조에 미치는 영향)

  • 윤만순;박영민
    • Journal of the Korean Ceramic Society
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    • v.40 no.1
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    • pp.37-45
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    • 2003
  • The dielectric and sintering characteristics of composites made by substituting Ca ion to Ba-site and Zr ion to Ti site in $(Ba{1-x}Ca_x)(Ti{0.96-yZr_ySn_{0.04})O_3$ (0.15x0.20,0.09y0.14) were investigated. As the content of Ca was more than 15 mol%, composite was formed by precipitating the second phase whose main element was CaTiO3 and the fraction of the second phase was increased. The curie temperature of composites was depended on Ca concentration, 1.7C per mol% and the maximum dielectric constant of composite was decreased by the rate of 200/mol%. The substitution of Zr ion decreased the curie temperature by the rate of 10C per mol% and the maximum dielectric constant was decreased by 217/mol% due to the increase of diffuse phase transition. The density and insulation breakdown characteristics were improved by suppressing the abnormal grain growth due to the increase of second phase. We developed the composition of Y5U (EIA standard) condenser which had high breakdown voltage and dielectric constant by controlling diffuse phase transition by the addition of Zr ion into composite.

Redox Characteristics of MO/Al2O3ZrO2 [M=Ni and Cu] Mixed Metal Oxides (MO/Al2O3ZrO2 [M=Ni 및 Cu] 혼합 금속 산화물의 환원-산화 특성)

  • Ryu, Jae-Chun;Kim, Young-Ho;Park, Chu-Sik;Hwang, Gab-Jin;Kim, Jong-Won
    • Journal of Hydrogen and New Energy
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    • v.16 no.1
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    • pp.49-57
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    • 2005
  • [ MO/Al2O3ZrO2 ](M=Ni and Cu) mixed metal oxides were prepared using sol-gel method in order to investigate the applicability to the 2-step thermo-chemical water splitting process and their redox behaviors were studied by temperature programmed reaction(TPR) from room temperature to 900C under 5% H2/Ar for the reduction and H2O/Ar for the oxidation, respectively. From the results, peaks of the reduction and the oxidation on temperature were shifted with the change of crystalline phases due to the addition of Al2O3 and ZrO2. The intensities of the peaks were also increased with the increase of contents of NiO or CuO that could be considered as active species. In addition, based on the observation of SEM images before and after the redox test, it seemed that Al2O3ZrO2 added prevented high temperature sintering of active metal components such as Ni (or Cu) on the surface and played a role of dispersing the active species homogeneously in solid solution of mixed oxides.

Effect of Dispersed MoO3 Amount on Catalytic Activity of NiO-ZrO2 Modified with MoO3 for Acid Catalysis

  • Sohn, Jong-Rack;Lee, Sung-Gyu;Shin, Dong-Cheol
    • Bulletin of the Korean Chemical Society
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    • v.27 no.10
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    • pp.1623-1632
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    • 2006
  • NiO supported on zirconia modified with MoO3 for acid catalysis was prepared by drying powdered Ni(OH)2Zr(OH)4 with ammonium heptamolybdate aqueous solution, followed by calcining in air at high temperature. The characterization of prepared catalysts was performed using FTIR, Raman, XRD, and DSC. MoO3 equal to or less than 15 wt% was dispersed on the surface of catalyst as two-dimensional polymolybdate or monomolybdate, while for MoO3 above 15 wt%, crystalline orthorhombic phase of MoO3 was formed, showing that the critical dispersion capacity of MoO3 on the surface of catalyst is 0.18 g/g NiO-ZrO2 on the basis of XRD analysis. Acidity and catalytic activities for acid catalysis increased with the amount of dispersed MoO3. The high acid strength and acidity was responsible for the Mo=O bond nature of the complex formed by the interaction between MoO3 and ZrO2. The catalytic activity for acid catalysis was correlated with the acidity of the catalysts measured by the ammonia chemisorption method.

The effect ofMnO2on the electrical properties in Pb(Zr, Ti)O3/-Pb(Mg, Nb)O3 (Pb(Zr, Ti)O3-Pb(Mg, Nb)O3MnO2첨가가 전기적 성질에 미치는 영향)

  • 김현재;조봉희;정형진;박창엽
    • Electrical & Electronic Materials
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    • v.1 no.2
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    • pp.152-161
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    • 1988
  • Pb(Zr, Ti)O3-Pb(Mg, Nb)O3계에 MnO2첨가량을 변화시켜 소결성, 미세구조, 유전상수, 비저항 및 압전특성에 미치는 영향을 XRD, EDAX 및 SEM을 이용하여 미세구조를 관찰하고 실험을 통하여 전기적 성질에 미치는 영향을 밝혔다. 비저항의 변화없이 그레인 성장이 억제되는 MnO2의 첨가량은 0.4wt%이었으며 이때 분말의 합성이 촉진되어 소성된 시편의 밀도가 증가하였다. 그러나 고상반응의 범위를 벗어나는 과잉 MnO2는 편석이 되어 그레인 경계상에 모임이 확인되었고 또한 기공을 형성하여 밀도를 낮추었다. Mn+4Mg+2 와 치환되어 페로브스카이트 구조의 "A" 결핍을 유발하였으며 이것이 비저강을 감소시키는 원인으로 밝혀졌다.감소시키는 원인으로 밝혀졌다.

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A Study on Sintering Behavior and Conductivity for NiO-doped BaZr0.85Y0.15O3-δ (NiO가 도핑된 BaZr0.85Y0.15O3-δ의 소결거동 및 전도도에 관한 연구)

  • Park, Young-Soo;Kim, Jin-Ho;Kim, Hae-Kyoung;Hwang, Kwang-Tak
    • Journal of Hydrogen and New Energy
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    • v.23 no.6
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    • pp.670-677
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    • 2012
  • Perovskite-type oxides such as doped barium zirconate (BaZrO3) show high proton conductivity and chemical stability when they are exposed to hydrogen and water vapour containing atmospheres, thus it can be applicable to the hydrogen separation and the fuel cell electrolyte membranes. However the high temperature (17001800C) and long sintering times (24h) are generally required to prepare the fully densified BaZrO3 pellets. These sintering conditions lead to the limitation of the grain size growth and the degradation of conductivity due to the acceleration of BaO evaporation at 1200C. Here we demonstrate NiO-doped BaZr0.85Y0.15O3δ with lower calcination and sintering temperature, less experimental procedure and lower process cost than the conventional mixing method. The stoichiometry of BaZr0.85Y0.15O3δ was optimized by the control of excess amount of Ba (5mol%) to minimized BaO evaporation. We found that the crystal size of NiO-doped BaZr0.85Y0.15O3δ was increased with increase of calcination temperature from XRD analysis. NiO-doped BaZr0.85Y0.15O3δ powder was calcined at 1000C for 12h when its showed the highest conductivity of 3.3×102s/cm.