Growth of Apatite-Type Lanthanide Silicates Single Crystals by the Floating Zone Method and Mechanism of Their Oxide Ionic Conduction
| Project/Area Number | 10450327 |
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
無機工業化学
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| Research Institution | HOKKAIDO UNIVERSITY |
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Principal Investigator |
KODAIRA Kohei Hokkaido Univ., Grad. School of Eng., Prof., 大学院・工学研究科, 教授 (60002002)
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| 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)
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| Project Period (FY) |
1998 – 1999
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| Project Status |
Completed(Fiscal Year 1999)
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| 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)
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| Keywords | rare-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 |
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| 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.
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Report
(3results)
Research Output
(10results)
