UO 2 samples doped with 6, 11, 22 mol% lanthanum were examined before and after air oxidation. To verify the formation of uranium-lanthanum-mixed oxide solid solutions, powder X-ray diffraction (XRD) analyses of the crystalline phases in the materials were carried out. The presence of oxygen vacancies in the La-doped UO 2 samples was identified by Raman spectrometry. It was evidenced by changes induced in the Raman spectra by air oxidation. This latter was carried out either by increasing the Raman laser power or by thermally treating the samples at 500 K for 370 h. In addition, oxidation behavior differences of pure and La-doped UO 2 samples were reported by comparing XRD and Raman results of the samples before and after air oxidation. It was shown that the concentration of the M 4 O 9 (M: U, La) phase increased with increasing content of La, whereas inhibition for the formation of M 3 O 8 phase was observed.

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Nanostructured palladium thin films Ͻ30 nm thick were prepared by pulsed laser deposition. X-ray diffraction investigations show that the Pd films are plastically deformed. Lattice strains are anisotropic and induced by the film growth mechanism as well as by the anisotropy of Young's modulus of palladium. In addition, a lattice contraction is observed near the surface. X-ray photoelectron spectroscopic analyses display a distinctive photoemission assigned to a less-ordered phase in addition to the common crystalline phase, which could be related to the grain boundaries. As a result, the electrochemical behavior of such Pd films clearly differs from that of common coarse-grained Pd. H-sorption and Pd oxide formation/removal processes greatly influence the subsequent film hydriding behavior, suggesting the occurrence of structural rearrangement/relaxation in the film. Hydride formation is favored when the film thickness decreases, which reflects the major role played by the subsurface layer on the hydriding process. The Pd films have a good stability upon hydrogen charge/discharge cycling which may be related to the lack of an abrupt ␣-to-␤ phase transition.

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