Hydrogenation and structural properties of Gd2Ni7 with superlattice structure |
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Authors: | Kenji Iwase Kazuhiro Mori Akinori Hoshikawa Toru Ishigaki |
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Affiliation: | 1. Frontier Research Center for Applied Sciences, Ibaraki University, 162-1 Shirakata, Tokai, Naka, Ibaraki 319-1106, Japan;2. Research Reactor Institute, Kyoto University, 2-1010 Asashiro-nishi, Kumatori, Sennan, Osaka 590-0494, Japan |
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Abstract: | The crystal structure and hydrogenation properties of Ce2Ni7-type Gd2Ni7 were investigated by X-ray diffraction (XRD) and the hydrogen pressure–composition (P–C) isotherm. Ce2Ni7-type Gd2Ni7 was obtained by annealing at 1523 K for 12 h and quenching in ice water. Two superlattice reflections (002 and 004) of the Ce2Ni7-type were clearly observed at 2θ = 7.3° and 14.6° in the XRD profile. The refined lattice parameters were a = 0.49662(9) nm and c = 2.4255(3) nm, respectively. Two plateaus were clearly observed during the absorption–desorption process in the P–C isotherm. The first and second plateaus were at 0.015 and 0.13 MPa, respectively, in the first desorption. The maximum hydrogen capacity reached was 1.13 H/M. The enthalpy and entropy were calculated as −20 kJ/mol H2 and −80 J/mol H2 K, respectively, from the van’t Hoff plot. After the P–C isotherm, the GdNi5 cell expanded by 2.15%, but the Gd2Ni4 cell shrank by 2.83%. |
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Keywords: | XRD Crystal structure P&ndash C isotherm Superlattice structure |
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