Japan Atomic Energy Agency : Press Releases

A face-centered-cubic lattice is found to a metal framework suitable to contain a mass of hydrogen commonly for rare-earth metals

Jul. 5, 2011

Hydrides of europium Eu, a rare-earth metal, was synthesized by hydrogenation of the metal powder with hydrogen fluid and their crystal structures and valence states were investigated synchrotron X-ray diffraction and Mössbauer spectroscopy measurements.

Europium hydride EuHx, when exposed to H₂ compressed to above 10 GPa (a hundred thousand atmospheric pressure), were found to exhibit the following structural and valence changes: orthorhombic (x=2; divalent) → hexagonal (x= 2; 7.2E.7 GPa) → tetragonal(x >2; 8.7E.7 GPa) → tetragonal (x> 2; 9.7 GPa~; trivalent). With a trivalent character, Eu³⁺H^-₃, and a distorted cubic fcc structure appearing above 9.7 GPa is the phase commonly observed for other rare-earth metal hydrides. The formation of trihydride of Eu was realized for the first time and Eu is no longer an irregular member of the rare-earth metal hydrides.

The results of the study was published in Physical Review Letters, 107, 025501(2011) on the 6th of July, 2011.

These findings were brought by the collaboration of Japan Synchrotron Radiation Research Institute (JASRI)/SPring-8, National Institute of Advanced Industrial Science and Technology (AIST), Quantum Beam Science Directorate, Japan Atomic Energy Agency (JAEA), and KYOKUGEN, Center for Quantum Science and Technology under Extreme Conditions, Osaka University. The research fund was supported by the New Energy Development Organization (NEDO) under Advanced Fundamental Research on Hydrogen Storage Materials.

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