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Y.E. Filinchuk, D. Sheptyakov, G. Hilscher, K. Yvon:
"Hydrogenation induced valence change and metal atom site exchange at room temperature in the C14-typesub-structure of CeMn_1.8Al_0.2H_4.4";
Journal of Alloys and Compounds, 356-357 (2003), 673 - 678.

Hydrogenation induced valence change and metal atom site exchange at room temperature in the C14-type sub-structure of CeMn1.8Al0.2H4.4

Y. E. Filinchuka, D. Sheptyakovb, G. Hilscherc and K. Yvon [Corresponding Author Contact Information] , [E-mail The Corresponding Author] , a

a Laboratoire de Cristallographie, University of Geneva, 24 Quai Ernest-Ansermet, CH-1211, Geneva 4, Switzerland
b Laboratory for Neutron Scattering, ETHZ & PSI, CH-5232, Villigen PSI, Switzerland
c Institut für Experimentalphysik, Technical University, Vienna, Austria

Received 27 August 2002; revised 1 October 2002; accepted 7 December 2002. ; Available online 19 March 2003.


Abstract

CeMn1.8Al0.2 absorbs more than 4.4 hydrogen atoms near ambient conditions, thereby undergoing a volume expansion ( [capital Delta, Greek] V/V~43%) that is the largest known among metal hydrides. While the Mn/Al distribution in the C14-type alloy [P63/mmc, a=5.37393(6), c=8.76321(12) Å] is partially ordered (preference of Al for site 2a), it tends to become disordered in the hydride (equal Mn/Al occupancies for sites 2a and 6h ). Only very slow hydrogenation while cooling the sample to -70 °C is capable of maintaining a partial Mn/Al order. Deuterium in CeMn1.8Al0.2D4.36(7) [a=5.9788(6), c=9.7600(13) Å] occupies exclusively tetrahedral Ce2(Mn,Al)2 type interstices. Magnetic susceptibility data suggest that the volume expansion during hydrogenation is enhanced by a valence change of cerium (CeIV [rightwards arrow] CeIII).

http://aleph.ub.tuwien.ac.at/F?base=tuw01&func=find-c&ccl_term=AC04405838

http://dx.doi.org/10.1016/S0925-8388(03)00123-3