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The European Physical Journal B
ISSN: 1434-6028 (printed version)
ISSN: 1434-6036 (electronic version)
Abstract Volume 2 Issue 4 (1998) pp 451-456
Lattice damage and Al-metal precipitation in 2.5 MeV-electron-irradiated AlH$\sf_3$
O.J. Zogal (1) (a), P. Vajda (2) (b), F. Beuneu (2), A. Pietraszko (1)
(1) Institute of Low-Temperature and Structure Research, Polish Academy of Sciences, 50-950 Wroclaw 2, Poland
(2) Laboratoire des Solides Irradiés, CNRS-CEA, École Polytechnique, 91128 Palaiseau, France
Received: 20 October 1997 / Revised: 24 December 1997 / Accepted: 30 January 1998
Abstract: AlH3 powder was bombarded with energetic electrons at 20 K and at room temperature and investigated by EPR, NMR, X-ray diffractometry, and microwave dielectric-constant measurements. The EPR spectra of the irradiated powder and of a selected single crystal cuboid of $\sim 10^{-1}$ mm edge show a complex asymmetric line centered at g = 2.009, with a Curie-like temperature dependence, attributed to radiation-induced color centers and/or their agglomerates. At the same time, the grains, which have become shiny black after irradiation, exhibit an increase of both the real and the imaginary part of $\varepsilon$. 27Al-NMR spectra of the irradiated powder present a Knight-shifted line at 1600(50) ppm, close to the position of bulk metallic Al, and corresponding to a concentration of c(Al) $\sim 10^{-2}$. In addition, the main hydride line differs from that before irradiation, demonstrating an alteration of environmental symmetry. The irradiation induces also a change in shape and width of the 1H-NMR line, another indication of symmetry change in the lattice. Finally, a refined X-ray single-crystal structure analysis of the irradiated cuboid indicates a change of structure from trigonal R-3c to R-3, with a loss of mirror symmetry for the two Al sites caused by the introduction of Al-defects in the vicinity of one of them.
PACS. 61.72.Ji Point defects (vacancies, interstitials, color centers, etc.) and defect clusters - 76.30.Mi Color centers and other defects - 76.60.Cq Chemical and Knight shifts
(a) email: zogal@int.pan.wroc.pl
(b) email: peter.vajda@polytechnique.fr
Online publication: June 2, 1998
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