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門野 良典*; 平石 雅俊*; 岡部 博孝*; 幸田 章宏*; 伊藤 孝
Journal of Physics; Condensed Matter, 35(28), p.285503_1 - 285503_13, 2023/07
被引用回数:0 パーセンタイル:0(Physics, Condensed Matter)Magnesium hydride has great potential as a solid hydrogen (H) storage material because of its high H storage capacity of 7.6 wt%. However, its slow hydrogenation and dehydrogenation kinetics and the high temperature of 300 C required for decomposition are major obstacles to small-scale applications such as automobiles. The local electronic structure of interstitial H in MgH is an important fundamental knowledge in solving this problem, which has been studied mainly based on density functional theory (DFT). However, few experimental studies have been performed to assess the results of DFT calculations. We have therefore introduced muon (Mu) as pseudo-H into MgH and investigated the corresponding interstitial H states by analyzing their electronic and dynamical properties in detail. As a result, we observed multiple Mu states similar to those observed in wide-gap oxides, and found that their electronic states can be attributed to relaxed-excited states associated with donor/acceptor levels predicted by the recently proposed ambipolarity model. This provides an indirect support for the DFT calculations on which the model is based via the donor/acceptor levels. An important implication of the muon results for improved hydrogen kinetics is that dehydrogenation, serving as a reduction for hydrides, stabilises the interstitial H state.
山川 浩二*; 知見 康弘; 石川 法人; 岩瀬 彰宏*
Journal of Alloys and Compounds, 370(1-2), p.211 - 216, 2004/05
被引用回数:1 パーセンタイル:12.39(Chemistry, Physical)Pd系希薄合金(Pd-1at.% Fe-H及びPd-1at.% Ag-H)における水素の移動について、50K付近の電気抵抗測定により調べた。0.5MeV電子線を15K以下で照射することにより不規則化した水素原子は、試料の昇温中に原子移動により規則化した。このときの電気抵抗の回復曲線には、電子線照射した試料では2つのサブステージが、急冷した試料では1つのステージのみが見られた。各ステージでの水素の移動エネルギーは、規則化に起因する電気抵抗変化をクロスカット法で解析することにより得られた。低温ステージでの移動エネルギーは高温ステージよりも小さく、高温ステージでの値は急冷の場合と同程度であった。Pd系合金に関して、照射による水素原子の不規則化と急冷によるものとの違いについて議論する。