Rare earth metal rich magnesium compounds RE{sub 4}NiMg (RE=Y, Pr-Nd, Sm, Gd-Tm, Lu)-Synthesis, structure, and hydrogenation behavior

Journal Article · Sun Feb 15 00:00:00 EST 2009 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2008.10.026· OSTI ID:21212182

Tuncel, Selcan ^[1]; Roquefere, Jean Gabriel; Stan, Cristina ^[2]; Bobet, Jean-Louis ^[2]; Chevalier, Bernard ^[2]; Gaudin, Etienne ^[2]; Hoffmann, Rolf-Dieter; Rodewald, Ute Ch ^[1]; Poettgen, Rainer ^[1]

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1. Institut fuer Anorganische und Analytische Chemie, Universitaet Muenster, Corrensstrasse 30, D-48149 Muenster (Germany)
2. CNRS, Universite de Bordeaux, ICMCB, 87 Avenue du Docteur Albert Schweitzer, F-33608 Pessac Cedex (France)

The rare earth metal rich compounds RE{sub 4}NiMg (RE=Y, Pr-Nd, Sm, Gd-Tm, Lu) were synthesized from the elements in sealed tantalum tubes in an induction furnace. All compounds were investigated by X-ray diffraction on powders and single crystals: Gd{sub 4}RhIn type, space group F4-bar 3m, Z=16, a=1367.6(2) pm for Y{sub 4}NiMg, a=1403.7(3) pm for Pr{sub 4}NiMg, a=1400.7(1) pm for Nd{sub 4}NiMg, a=1386.5(2) pm for Sm{sub 4}NiMg, a=1376.1(2) pm for Gd{sub 4}NiMg, a=1362.1(1) pm for Tb{sub 4}NiMg, a=1355.1(2) pm for Dy{sub 4}NiMg, a=1355.2(1) pm for Ho{sub 4}NiMg, a=1354.3(2) pm for Er{sub 4}NiMg, a=1342.9(3) pm for Tm{sub 4}NiMg, and a=1336.7(3) pm for Lu{sub 4}NiMg. The nickel atoms have trigonal prismatic rare earth coordination. These NiRE{sub 6} prisms are condensed via common edges to a three-dimensional network which leaves voids for Mg{sub 4} tetrahedra and the RE1 atoms which show only weak coordination to the nickel atoms. The single crystal data indicate two kinds of solid solutions. The RE1 positions reveal small RE1/Mg mixing and some compounds also show Ni/Mg mixing within the Mg{sub 4} tetrahedra. Y{sub 4}NiMg and Gd{sub 4}NiMg have been tested for hydrogenation. These compounds absorb up to eleven hydrogen atoms per formula unit under a hydrogen pressure of 1 MPa at room temperature. The structure of the metal atoms is maintained with only an increase of the lattice parameters ({delta}V/V{approx}22%) if the absorption is done at T<363 K as at higher temperature a decomposition into REH{sub 2}-REH{sub 3} hydrides occurred. Moreover, the hydrogenation affects drastically the magnetic properties of these intermetallics. For instance, Gd{sub 4}NiMg exhibits an antiferromagnetic behavior below T{sub N}=92 K whereas its hydride Gd{sub 4}NiMgH{sub 11} is paramagnetic down to 1.8 K. - Graphical abstract: The Mg{sub 4} and NiGd{sub 6} units in Gd{sub 4}NiMg and Gd{sub 4}NiMgH{sub x}.

• OSTI ID: 21212182
• Journal Information: Journal of Solid State Chemistry, Vol. 182, Issue 2; Other Information: DOI: 10.1016/j.jssc.2008.10.026; PII: S0022-4596(08)00539-2; Copyright (c) 2008 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ABSORPTION
ANTIFERROMAGNETISM
CUBIC LATTICES
DECOMPOSITION
GADOLINIUM COMPOUNDS
HYDRIDES
HYDROGEN
HYDROGENATION
INDUCTION FURNACES
INTERMETALLIC COMPOUNDS
LATTICE PARAMETERS
LUTETIUM COMPOUNDS
MAGNETIC PROPERTIES
MONOCRYSTALS
NEODYMIUM COMPOUNDS
NICKEL COMPOUNDS
PRASEODYMIUM COMPOUNDS
PRESSURE RANGE MEGA PA 01-10
SAMARIUM COMPOUNDS
SOLID SOLUTIONS
SPACE GROUPS
SYNTHESIS
TANTALUM
TEMPERATURE RANGE 0273-0400 K
THULIUM COMPOUNDS
VOIDS
X-RAY DIFFRACTION