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Quantitative Atomic-Site Analysis of Functional Dopants/Point Defects in Crystalline Materials by Electron-Channeling-Enhanced Microanalysis
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Crystal Structure Analysis of La2Ni6CoD(x) During Deuterium Absorption Process
Kenji Iwase1, Kazuhiro Mori2, Suguru Tashiro1
1Department of Materials Science and Engineering, Ibaraki University , 4-12-1, Nakanarusawa, Hitachi 316-8511, Japan.
Inorganic Chemistry
|August 13, 2015
Summary
This study reveals the crystal structures of lanthanum-nickel-cobalt deuterides (La2Ni6CoD(x)) using neutron diffraction. Deuterium absorption leads to phase transformations from hexagonal to orthorhombic and monoclinic structures.
Area of Science:
- Materials Science
- Solid State Chemistry
- Crystallography
Background:
- Lanthanum-nickel-cobalt alloys are investigated for hydrogen storage applications.
- Understanding the structural changes upon deuterium absorption is crucial for material design.
Purpose of the Study:
- To determine the crystal structures of La2Ni6CoD(x) at different deuterium concentrations (x = 5.2 and 9.6).
- To elucidate the phase transformation sequence during the initial deuterium absorption process.
Main Methods:
- In situ neutron diffraction was employed to analyze the crystal structures.
- The study was conducted along the pressure-composition (P-C) isotherm.
Main Results:
- La2Ni6CoD(5.2) (phase I) exhibited an orthorhombic structure with specific lattice parameters and deuterium sites within MgZn2-type and CaCu5-type cells.
- La2Ni6CoD(9.6) (phase II) showed a monoclinic structure with distinct lattice parameters and increased deuterium occupation.
- A phase transformation sequence from hexagonal to orthorhombic (phase I) and finally to monoclinic (phase II) was observed.
Conclusions:
- Deuterium absorption in La2Ni6Co induces phase transformations with decreasing symmetry.
- The distribution and occupation of deuterium atoms vary significantly across different crystallographic sites and phases.
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