| Project/Area Number |
18K04677
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Review Section |
Basic Section 26010:Metallic material properties-related
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| Research Institution | Tohoku University |
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Principal Investigator |
Fujita Nobuhisa 東北大学, 多元物質科学研究所, 講師 (70431468)
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| Project Period (FY) |
2018-04-01 – 2022-03-31
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| Project Status |
Completed (Fiscal Year 2021)
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| Budget Amount *help |
¥4,290,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥990,000)
Fiscal Year 2021: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000)
Fiscal Year 2020: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
Fiscal Year 2019: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
Fiscal Year 2018: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000)
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| Keywords | 準結晶 / 近似結晶 / 複雑合金 / 合金状態図 / 構造安定性 / 構造解析 / 結晶構造解析 / 構造相転移 / 荷電子濃度則 / 相平衡 / 構造形成マップ / 価電子濃度則 / 軌道混成効果 / 原子半径比 / 荷電子濃度 / 二相共存 / 荷電子数 / 正二十面体準結晶 / 相図 / 第一原理計算 / 相形成マップ |
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| Outline of Final Research Achievements |
By synthesizing many alloy samples with different choices of elements and mixing ratios, the formation behaviors of complex alloy phases, namely, icosahedral quasicrystals and their approximants, in the Al-Pd-TM (=transition metal) and Cd-Mg-RE (=rare earth element) systems were studied in detail. A few novel complex alloy crystals including an unconventional 1/1 approximant in the Cd-Mg-Ce system were discovered. Moreover, the crystal structures were determined for some of the approximants using single-crystal X-ray diffraction technique. Meanwhile, a new mapping method was examined in order to reveal any universal trends in the formation behaviors irrespective of TM species. In this method, compositions of related phases were projected onto a planar map in which the mean number of valence electrons per atom and the vacant fraction of d-orbitals as calculated from the composition were used as the orthogonal coordinate axes.
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| Academic Significance and Societal Importance of the Research Achievements |
準結晶や様々な近似結晶の相形成挙動に関する調査は、準結晶の発見から長きにわたり世界中で行われてきた。これらの新規複雑合金相の探索指針として固溶合金に対するヒュームロザリー則が適用されてきたが、元素置換による構造変化には電子の干渉効果に加えて軌道混成効果の影響も無視できず，その詳細なメカニズムの理解は道半ばである。本研究では元素の部分置換による相形成挙動の変化を系統的に調査するとともに、平均価電子濃度やd軌道空席率等を座標軸とするマッピング法を考案することで、準結晶や近似結晶の普遍的な形成挙動を部分的にあぶりだした。この試みをさらに進めれば、構造変化の支配因子を解明できると期待できる。
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