Disproportionation reaction of LaH2 at high pressure and low temperature

18th APS-SCCM; 24th AIRAPT

Machida, A.^1 ; Watanuki, T.^1 ; Kawana, D.^2 ; Aoki, K.^1,3

Quantum Beam Science Directrte., Japan Atomic Energy Agency, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo

679-5148, Japan^1

High Energy Accelerator Research, Organization (KEK), 1-1 Oho, Ibaraki, Tsukuba

305-0801, Japan^2

Institute for Materials Research, TohokuUniversity, 2-1-1 Katahira, Sendai

980-8577, Japan^3

关键词: Disproportionation reactions;    Disproportionations;    FCC metals;    High pressure;    Interstitial hydrogen;    Low temperatures;    Synchrotron radiation x-ray diffractions;    Tetrahedral sites;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/500/2/022001/pdf
DOI  :  10.1088/1742-6596/500/2/022001

来源: IOP

【 摘 要 】

Structural change of LaH2has been investigated at high pressure and low temperature by synchrotron radiation X-ray diffraction. LaH2has an fcc metal lattice with interstitial hydrogen atoms located at tetrahedral sites. The fcc-LaH2decomposes into two phases, which have different hydrogen compositions such as hydrogen-poor LaH and hydrogen -rich LaH2+δphases, at 11 GPa at room temperature. In spite of largely suppressed diffusivity of the interstitial hydrogen atoms at low temperature, we have found the disproportionation reaction around 14 GPa at 200 K. Difference in the molar volume between each phases suggests monohydride LaH is formed as the disproportionation product even at low temperature. The volume fraction of the hydrogen-poor phase relative to the hydrogen-rich one at 200 K rapidly rises against pressure and reaches to ∼0.45 at ∼17 GPa.