For the first time combined X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) experiments were carried out to probe the short- and long-range order in lanthanum-modified PbTiO3 ceramic materials (Pb1 - x La x TiO3) for x ranging from 0 to 30 atom % of La. XRD results show that a tetragonal structure fitted well to all samples, except to the one with 30 atom % of La for which XRD results highlighted a cubic unit cell. XRD refinements also confirmed the existence of only A-site vacancies. X-ray absorption near edge spectroscopy (XANES) measurements indicate that the local structure around Ti atoms has a different compositional dependence from the one obtained from XRD, mainly for the sample with 30 atom % of La. According to XANES data, for the sample with 30 atom % of La, a local distortion around Ti atoms persist. The analysis of extended X-ray absorption fine structure (EXAFS) spectra shows a decrease in the local disorder around Ti atoms as the content of La increases. Structural details, in terms of short and long-range order, are presented and the correlation between the XRD and XANES/EXAFS data is discussed.

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Electrochemistry / Electropolymerization / Organic media / Uranium / Neptunium / a Spectrometry sources / Polyacrylonitrile SummaryThe electrochemical reduction of uranium and neptunium ions is achieved in aprotic solvents in presence of acrylonitrile. The cathodic deposit on a usual metal consists of a grafted polyacrylonitrile layer in which actinide oxide or actinide metal has been inserted as a consequence of the overall cathodic reaction. As polyacrylonitrile is an insulating material, the electrochemical polymerization reaction is stopped when the polymer layer thickness reaches 1000 A at maximum.The material we thus produced may be used as an alpha spectroscopy source and we report here the results originating from the preparation of more than hundred samples. -ECI V) Fig. 1. Voltammetric two-step reduction of acrylonitrile (0.1 M) in AN with Et 4 NC10 4 , 0.05 M; Ni electrode, total surface: 2 cm 2 ; υ = 50 mV s" 1 .