| Numéro |
J. Phys. Colloques
Volume 47, Numéro C8, Décembre 1986
EXAFS and Near Edge Structure IV
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|---|---|---|
| Page(s) | C8-931 - C8-935 | |
| DOI | https://doi.org/10.1051/jphyscol:19868179 | |
J. Phys. Colloques 47 (1986) C8-931-C8-935
DOI: 10.1051/jphyscol:19868179
X-RAY ABSORPTION STUDIES OF MIXED-VALENT RARE EARTH CLUSTERS
W. NIEMANN1, W. MALZFELDT2, P. RABE3 et M. LÜBCKE41 Haldor Topsoe Research Laboratories, DK-2800 Lyngby, Denmark
2 IBM, Yorktown Heights, NY 10598, U.S.A.
3 Fachhochschule Ostfriesland, D-2970 Emden, F.R.G.
4 C.H.F. Müller, Unternehmensbereich der Philips GmbH, D-2000 Hamburg 63, F.R.G.
Abstract
The transition from atomic to metallic valences in small matrixisolated clusters of Sm, Nd and Pr has been studied by XANES- and EXAFS-measurements at the corresponding L3-edges. The observed valence of the Rare Earth clusters depends on the atomic concentrations and on the type of metal atom. Hints on the cluster size are given by annealing the samples to temperatures near the melting point of the Rare Gas matrix. In Nd and Pr samples a complete valence change from 2 to 3 has been observed within an atomic concentration range of 0.1 to 0.25 % metal content. Clusters containing more than 4 - 6 atoms are totally trivalent. For Sm a valence transition is observed at 1 % metal concentration, the valence rising from 2.0 to 2.6. From EXAFS data a critical cluster size of K = 13 atoms at v = 2.6 has been elaborated. Sm clusters with K > 13 are mixed valent.