Variable incidence angle - X-ray absorption spectroscopy for the study of Zircaloy corrosion layers

Variable incidence angle X-ray absorption fine structure (VIAXAFS) spectroscopy has been used for its non-destructive ability to probe and investigate nano-structures in zirconia films. The theory of X-ray absorption-detection in fluorescence mode was revisited and applied to the variable incidence angles of the photon beam for studying a corrosion film. The expression derived for the depth profile was used to evaluate nano-structures and atom environments in the film. This technique was applied, spanning angles from a grazing towards normal incidence on a sample layer obtained by zirconium alloy corrosion. XAFS analysis on the Zr K edge suggests a lower number of next neighbour Zr atoms in the corroded samples. This may be due to the relative density for given average atom distances suggesting a high density of dislocations and defects. The discussion underlines that the technique reveals nano-pores, dislocations, vacancies or defect features. The presence of tetragonal zirconia is not observed for zirconium alloy corrosion layers.