Investigation of coloration defects in porous zirconium by X-ray photoelectron spectroscopy

Given the importance of zirconium in a wide variety of applications, defect identification, isolation, and prevention is critical. In this study, an unknown coloration defect on the surface of porous industrial zirconium sponge is assessed. Various microscopy and spectroscopy techniques (energy dispersive X-ray spectroscopy mapping, X-ray photoelectron spectroscopy depth profiling, and Raman spectroscopy) are implemented to assist with characterization of impurities and compound identification. The combined effect of sample porosity and overlap of core-shell excitations provides a unique challenge in spectrum analysis, particularly with respect to background function computation. Various curve fitting and data analysis techniques are applied and compared in order to weigh their efficacy in quantifying the chemical state and other characteristics of the specimen. Peak-specific cumulative distribution functions are weighed against the Shirley background in terms of their impact on reliable spectrum quantification. In addition, the quantification merits of various peak functional forms and techniques for establishing reliable fitting in depth profiles are discussed. These analyses suggests that the defect film is zirconium dioxide colorized by trace impurities (principally Fe, Cl, and Mg). - Highlights: • A thin-film coloration defect on zirconium sponge is characterized and identified. • A curve fitting methodology and background model for XPS spectra is proposed. • Benefits of the curve fitting model are identified. • Possible mechanisms for the formation of the film are discussed.