• Title/Summary/Keyword: Oxide superconductors

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Peculiarities of SHS and solid state synthesis of $ReBa_{2}Cu_{3}O_{7-x}$ materials

  • Sho, Dea-Wha;Li, Yingmei;Cho, Yong-Joon;Kim, Tae-Wan;Korobova, N.;Isaikina, O.;Mansurov, Z.;Baydeldinova, A.;Ksandopoulo, G.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.07a
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    • pp.620-623
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    • 2001
  • The peculiarities of using Self-propagating High-temperature Synthesis (SHS) and solid state phase synthesis for production of high temperature superconductor materials are discussed. Oxide superconductors with general formula $ReBa_2$$Cu_3$$O_{7-x}$ (Re= Y, Yb, Sm, Nd) have been made with using barium oxide initial powder instead of traditional barium carbonate. X-ray powder diffraction showed a single phase orthorhombic perovskite structure was produced in all reactions. Phenomena observed during the grinding of the reactant mixture are presented. Mechano-chemical activation - as a pretreatment of the reactant mixture - strongly influences the kinetic parameters, the reaction mechanism, and the composition and structure of the final product.

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Peculiarities of SHS and Solid State Synthesis of ReBa2Cu3O7-x Materials

  • Soh, Deawha;Natalya, Korobova
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.15 no.3
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    • pp.275-280
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    • 2002
  • The peculiarities of using Self-propagating High-temperature Synthesis (SHS) and solid-stave chase synthesis for production of high temperature superconductor materials were discussed. Oxide superconductors with general formula of $ReBa_2Cu_3O_{7-x}$ (Re=Y, Sm) haute been made by using barium oxide initial powder instead of traditional barium carbonate. Phenomena observed during the grinding of the reactants mixture are presented. Mechano-chemical activation - as a pre-treatment of the reactants mixture - strongly influences the kinetic parameters, the reaction mechanism, and the composition and structure of the final product.

An analysis method of reflectance spectra of strongly correlated electron systems

  • Hwang, Jungseek
    • Progress in Superconductivity and Cryogenics
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    • v.15 no.1
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    • pp.14-18
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    • 2013
  • We introduce a generic method to analyze optical 17reflectance spectra of strongly correlated electron systems including high-temperature superconductors by using an extended Drude model and Allen's approach. We explain the process step by step from reflectance through the optical conductivity and the scattering rate to the bosonic spectral function. Through the process we are able to get important information on the interactions between charge carriers from measured optical conductivity of the strongly correlated electron systems including copper oxide and iron pnitide high temperature superconductors.

Preparation of Phase Pure Cuprate Superconductors via The Modification of Sol-Gel Method

  • Ahn, Beom-Shu
    • Journal of the Korean Applied Science and Technology
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    • v.17 no.2
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    • pp.144-148
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    • 2000
  • A modification of the sol-gel method to obtain phase pure superconducting oxides is described. The method starts from organic salts of yttrium, barium and copper, such as acetates, and avoids the sudden and uncontrollable decomposition of the organic fraction which occurs if nitrates are used as starting materials. The aqueous solution obtained with citric acid in an alkaline medium is concentrated under vacuum. The solid so prepared is decomposed at about $300^{\circ}C$ thus giving an oxide precursor containing well dispersed yttrium, barium and copper. Pyrolysis at 850 - $920^{\circ}C$ followed by oxygen annealing gives the superconducting orthorhombic 123 phase. The results of TGA/DTA of the precursor, as well as XRD, electrical and magnetic property measurements on the pyrolysis products are presented and discussed.

Results of the First Round-Robin-Test for Evaluation of Mechanical Properties in Bi-2223 Composite Superconductors (산화물 복합초전도체(Bi-2223)의 기계적특성 평가를 위한 라운드로빈 시험 결과)

  • 신형섭
    • Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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    • 2001.02a
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    • pp.13-16
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    • 2001
  • In the practical sense, it is important to assess the Young modulus and the degradation of $I_{c}$ due to mechanical deformation in HTS tapes for designing superconducting magnets. In order to establish a test method of mechanical properties in oxide composite superconductors, the committee of VAMAS/TWA 16-Subgroup proposed an international round robin test. The first effort has been focused on the multifilamentary Bi-2223 tapes. Eight groups participated in the RRT activity and each group carried out the tensile test by their own professional technique to three kinds of Bi-2223 tapes. The experimental details were reported and discussed for your information.

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A New Method of HTS Material Synthesis by Combination of MCA and SHS

  • Korobova, N.;Soh, Dea-Wha
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.07b
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    • pp.1270-1273
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    • 2004
  • The combination of methane-chemical activation and Self-propagating High-temperature synthesis (SHS) has widened the possibilities for both methods. For YBCO systems the investigation showed that a short-term mechano-chemical activation of initial powders before SHS leads to single-phase and ultra-fine products. A new technique for preparation ultra-fine high-temperature superconductors of YBCO composition with a grain size d < $1{\mu}m$ is developed. The specific feature of the technique is formation of the $YBa_2Cu_3O_{7-x}$ crystalline lattice directly from an X-ray amorphous state arising as a result of mechanical activation of the original oxide mixture. The technique allows the stage of formation of any intermediate reaction products to be ruled out. X-ray and magnetic studies of ultra-fine high temperature superconductors (HTS) are carried out. Dimension effects associated with the microstructure peculiarities are revealed. A considerable enhancement of inter-grain critical currents is found to take place in the ultra-fine samples investigated.

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Microstructure and Prooperties of Y-Ba-Cu-O Superconductor Fabricated by Hot Isostatic Pressing (열간정수압소결(HIP)시킨 Y-Ba-Cu-O 초전도체의 조직과 특성)

  • 신미남;백수현;송진태
    • Journal of the Korean Ceramic Society
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    • v.26 no.2
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    • pp.267-275
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    • 1989
  • YBa2Cu3O7-x oxide superconductors were fabricated by sintering and hotisostatic pressing (HIP), and their microstructures and properties were compared with each other. Thougha part of the second phase was observed along grain boundaries, their structures were consisted of single (123) phase and they had many porosities. But, porosities were remakably reduced by Hiping and the densification was brought about. The structure of (123) compound also showed a number of twins, which are typical of high Tc superconductors. The on-set temperature of YBa2Cu3O7-x compound sintered at 96$0^{\circ}C$ in oxygen and hipped at 88$0^{\circ}C$ was highest, but that shwoed 0 resistance at 87$^{\circ}$K, which is a little lower than the compound sintered at 96$0^{\circ}C$. HIP treatment also increased the critical current density of as-sintered compound. However, its value was low, which may be ascribed to the many pores of starting-sintered compact and partially to the second phase along grain boundaries.

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