title: Crystal structure and cyclic hydrogenation property of Pr4MgNi19.
abstract: The hydrogen absorption-desorption property and the crystal structure of Pr4MgNi19 was investigated by pressure-composition isotherm measurement and X-ray diffraction (XRD). Pr4MgNi19 consisted of two phases: 52.9% Ce5Co19-type structure (3R) and 47.0% Gd2Co7-type structure (3R). Sm5Co19-type structure (2H) and Ce2Ni7-type structure (2H) were not observed in the XRD profile. The Mg atoms substituted at the Pr sites in a MgZn2-type cell. The maximum hydrogen capacity reached 1.14 H/M (1.6 mass%) at 2 MPa. The hysteresis factor, Hf = ln(Pabs/Pdes), was 1.50. The cyclic hydrogenation property of Pr4MgNi19 was investigated up to 1000 absorption-desorption cycles. After 250, 500, 750, and 1000 cycles, the retention rates of hydrogen were reduced to 94%, 92%, 91%, and 90%, respectively. These properties were superior to those of Pr2MgNi9 and Pr3MgNi14.
authors.affiliation: Department of Materials Science and Engineering, Ibaraki University , 4-12-1, Nakanarusawa, Hitachi, Ibaraki 316-8511, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Iwase
authors.forename: Naoyoshi
authors.initials: N
authors.lastname: Terashita
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Mori
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Yokota
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Suzuki