Investigation of modification of hydrogenation and structural properties of LaNi{sub 5} intermetallic compound induced by substitution of Ni by Pd

Journal Article · Sat Jan 15 00:00:00 EST 2011 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2010.10.037· OSTI ID:21494180

Prigent, J ^[1]; Gupta, M ^[2]

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1. Chimie Metallurgique des Terres Rares, Institut de Chimie et Materiaux Paris-Est, CNRS, Universite Paris-Est, 2-8 rue H. Dunant, 94320 Thiais Cedex (France)
2. Laboratoire de Thermodynamique et Physico-Chimie des Hydrures et Oxydes, Universite Paris-Sud Orsay, Bat. 415, 91405 Orsay (France)

The hydrogenation properties of the LaNi{sub 5} (CaCu{sub 5} type, hP6, P6/mmm) and Pd substituted derivatives LaNi{sub 5-x}Pd{sub x} compounds have been studied in the whole homogeneity range of the solid solution (0.25{<=}x{<=}1.5). The pressure versus hydrogen content isotherms show several plateaus and an increase of the plateau pressure as a function of palladium concentration. The volume increase of the Pd substituted alloys should have resulted in a lowering, and not an increase, of the plateau pressure, according to the conventional models based on the size effect. In order to elucidate the origin of this anomalous behavior, both an experimental and a theoretical ab initio electronic structure investigation have been carried out. Experimentally, the nature and the structural properties of the hydrides have been studied by both in situ and ex situ neutron diffraction. The crystal structures of the three hydride phases are reported (LaNi{sub 3.5}Pd{sub 1.5}D{sub 1.96}, filled-up CaCu{sub 5} type, P6/mmm; LaNi{sub 4}PdD{sub 2.72}, LaNi{sub 2}(Ni{sub 0.75}Pt{sub 0.25}){sub 3}H{sub 2.61} type, oI128, Ibam; LaNi{sub 4.75}Pd{sub 0.25}D{sub 5.67}, partly ordered CaCu{sub 5} type, P6mm). In addition, the phase diagram of LaNi{sub 5-x}Pd{sub x}-H system has been investigated. The electronic and thermodynamic properties of both intermetallic compounds and the hydrides have been studied by ab initio electronic structure calculations. The theoretical results are in good agreement with our experimental data, and show that electronic interactions play a major role in the hydrogenation behavior of these Pd substituted intermetallic compounds, and that these effects cannot be accounted for by a simplistic model based on the size effect alone. -- Graphical abstract: Phase diagram of the system LaNi{sub 5-x}Pd{sub x}-D{sub 2} (absorption) at 25 {sup o}C and 25 bar. Display Omitted

• OSTI ID: 21494180
• Journal Information: Journal of Solid State Chemistry, Vol. 184, Issue 1; Other Information: DOI: 10.1016/j.jssc.2010.10.037; PII: S0022-4596(10)00494-9; Copyright (c) 2010 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ABSORPTION
ELECTRONIC STRUCTURE
HEXAGONAL LATTICES
HYDRIDES
HYDROGEN
HYDROGEN STORAGE
HYDROGENATION
INTERACTIONS
INTERMETALLIC COMPOUNDS
LANTHANUM ALLOYS
NEUTRON DIFFRACTION
NICKEL ALLOYS
ORTHORHOMBIC LATTICES
PALLADIUM ALLOYS
PHASE DIAGRAMS
SOLID SOLUTIONS
TEMPERATURE RANGE 0273-0400 K
THERMODYNAMIC PROPERTIES
ALLOYS
CHEMICAL REACTIONS
COHERENT SCATTERING
CRYSTAL LATTICES
CRYSTAL STRUCTURE
DIAGRAMS
DIFFRACTION
DISPERSIONS
ELEMENTS
HOMOGENEOUS MIXTURES
HYDROGEN COMPOUNDS
INFORMATION
MIXTURES
NONMETALS
PHYSICAL PROPERTIES
PLATINUM METAL ALLOYS
RARE EARTH ALLOYS
SCATTERING
SOLUTIONS
SORPTION
STORAGE
TEMPERATURE RANGE
TRANSITION ELEMENT ALLOYS