Abnormal lattice behavior of MgH2 in isotope labeled LiBD4-MgH2 composites at the melting of LiBD4

• Published in: Journal of alloys and compounds Vol. 808; p. 151640
• Main Authors: Cho, In Hwa, Gang, Seunggi, Choi, Yong Nam, Lee, Heeju, Park, Mirae, Shim, Jae-Hyeok, Noh, Do Young
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 05-11-2019; Elsevier BV
• Subjects: Composite materials; Diffusion; Hydrogen storage; In situ neutron diffraction; In situ x-ray diffraction; LiBH4-MgH2 composite; Melt temperature; Melting points; Neutron diffraction; Neutrons; Unit cell; Hydrogen storage; In situ x-ray diffraction; LiBH4-MgH2 composite; In situ neutron diffraction
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2019.07.352

We found abnormal lattice behavior of MgH2 in LiBD4-MgH2 composites at the melting of LiBD4 using high resolution x-ray diffraction measurements. At the LiBD4 melting point, the tetragonal MgH2 unit cell contracted isotropically which is attributed to D atoms diffused from neighboring LiBD4; these D atoms can occupy interstitals or lattice points of MgH2. Endothermic behavior of LiBD4 during melting might also have contriubuted to the contraction of MgH2. In addition, the intensity of MgH(D)2 Bragg peaks measured in in situ neutron diffraction experiment confirms that H/D exchange between the two hydrides starts below the LiBD4 melting temperature.
•In LiBD4-MgH2, the MgH2 unit-cell contracts at the LiBD4 melting.•Before LiBD4 melts, H/D exchanged MgH(D)2 phases are confirmed.•The c/a ratio of MgH2 increases after LiBD4 melts.