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Growth of Apatite-Type Lanthanide Silicates Single Crystals by the Floating Zone Method and Mechanism of Their Oxide Ionic Conduction

Research Project

Project/Area Number10450327
Research Category

Grant-in-Aid for Scientific Research (B)

Allocation TypeSingle-year Grants
Section一般
Research Field 無機工業化学
Research InstitutionHOKKAIDO UNIVERSITY

Principal Investigator

KODAIRA Kohei  Hokkaido Univ., Grad. School of Eng., Prof., 大学院・工学研究科, 教授 (60002002)

Co-Investigator(Kenkyū-buntansha) NAKAYAMA Susumu  Niihama National College of Technology, Lec., 講師 (50300637)
HIGUCHI Mikio  Hokkaido Univ., Grad. School of Eng., Inst., 大学院・工学研究科, 助手 (40198990)
Project Period (FY) 1998 – 1999
Project Status Completed(Fiscal Year 1999)
Budget Amount *help
¥12,100,000 (Direct Cost : ¥12,100,000)
Fiscal Year 1999 : ¥3,800,000 (Direct Cost : ¥3,800,000)
Fiscal Year 1998 : ¥8,300,000 (Direct Cost : ¥8,300,000)
Keywordsrare-earth silicates / oxide ionic conductor / apatite structure / floating zone method / single crystals / conductivity / anisotropy / 酸素イオン伝導体 / 非化学量論性 / 導電率の異方性
Research Abstract

Lanthanide silicates with an apatite structure are a new type of oxide ionic conductors; at low temperatures blow 600 ℃ the conductivities of these materials are superior to that of stabilized zirconia. However, no large-size single crystals of these materials have so far been grown, and accordingly their essential properties have not yet clarified. In this study, single crystals of apatite-type lanthanide silicates were grown by the floating zone method and their electrical properties were evaluated.
From the viewpoint of light-absorption, praseodymium, neodymium and samarium silicates crystals were grown. All the crystals were easily grown by the floating zone method since they melt congruently. For the Nd-system, bubble inclusions were occasionally contained but the use of a Nd-poor feed rod enabled to grow an inclusion-free crystal. The congruent composition may be different form the stoichiometric one and is located at Nd-poor side. For the Sm-system, macroscopic defect-free crystals have not yet been obtained due to the formation of microcracks. Since the cracks were formed parallel to the c-plane, however, they do not hinder significantly the measurements of conductivities. For all the kinds of crystals, the conductivities parallel to the c-axis were larger by about one order of magnitude than those perpendicular to the c-axis. These results proved that the oxide ions at 2a site migrate preferentially through the channel parallel to the c-axis of the apatite structure. The conductivities of the single crystals were independent on the kinds of rare-earth ions although remarkable decrease in the conductivities were observed for the sintered compacts. This is because the oxide ions at 2a site is coordinated by three rare-earth ions at 6h site on the same plane level.

Report

(3results)
  • 1999 Annual Research Report   Final Research Report Summary
  • 1998 Annual Research Report

Research Products

(10results)

All Other

All Publications

  • [Publications] S.Nakayama: "Oxide Ionic Conductivity of Apatite Type Nd_<9.33>(SiO_4)_6O_2 Single Crystal"J.Eur.Ceram.Soc.. 19. 507-510 (1999)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1999 Final Research Report Summary
  • [Publications] M.Higuchi: "Growth of Aptite-Type Neodymium Silicate Single Crystals by the Floating-Zone Method"J.Crystal Growth. 207. 298-302 (1999)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1999 Final Research Report Summary
  • [Publications] S.Nakayama: "Ionic Conductivity of Aptite-Type Ndx(SiO_4)_6O_<1.5X-12>(X=9.20 and 9.33)"J.Mater.Sci.Let.. (in press).

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1999 Final Research Report Summary
  • [Publications] M. Higuchi, K. Kodaira and S. Nakayama: "Growth of Apatite-type Neodymium Silicate Single Crystals by the Floating-Zone Method"J. Crystal Growth. 207. 298-302 (1999)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1999 Final Research Report Summary
  • [Publications] S. Nakayama, M. Sakamoto, M. Higuchi, K. Kodaira, M. Sato, S. Kakita, T. Suzuki, K. Itoh: "Oxide lonic Conductivity of Apatite Type NdィイD29.33ィエD2(SiOィイD24ィエD2)ィイD26ィエD2OィイD22ィエD2 Single Crystal"J. Eur. Ceram. Soc.. 19. 507-510 (1999)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1999 Final Research Report Summary
  • [Publications] S. Nakayama, M. Sakamoto, M. Higuchi and K. Kodaira: "Ionic Conductivities of Apatite Type NdィイD2xィエD2(SiOィイD24ィエD2)ィイD26ィエD2OィイD21.5x-12ィエD2 (x=9.20 and 9.33) Single Crystals"J. Mater. Sci. Let.. (in press).

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1999 Final Research Report Summary
  • [Publications] S .Nakayama: "Oxide Ionic Conductivity of Apatite Type Nd_<9.33>(SiO_4)_6O_2 single Crystal"J. Eur. Ceram. Soc.. 19. 507-510 (1999)

    • Related Report
      1999 Annual Research Report
  • [Publications] M. Higuchi: "Growth of Apatite-Type Neodymium Silicate Single Crystals by the Floating-Zone Method"J. Crystal Growth. 207. 298-302 (1999)

    • Related Report
      1999 Annual Research Report
  • [Publications] S. Nakayama: "Ionic Conductivity of Apatite-Type Nd_x(SiO_4)_6O_<1.5x-12> (x=9.20 and 9.33) Single Crystals"J. Mater. Sci. Let.. (in press).

    • Related Report
      1999 Annual Research Report
  • [Publications] S.Nakayama: "Oxide Ionic Conductivity of Apatite Type Nd_<9.33>(S_2O_4)_6O_2 Single Crystal" J.Eur.Ceram.Soc.,. (in press).

    • Related Report
      1998 Annual Research Report

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Published : 1998-04-01   Modified : 2016-04-21  

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