Dependence of surface composition of Zr ? Ni intermetallic compounds on their bulk composition and heat treatment

X-ray photoelectron spectroscopy (ESCA) was used to study the dependence of Zr2Ni, ZrNi and ZrNi5 intermetallic compound surface compositions upon duration of heating in air at 200 °C. The changes in relative intensities of Zr 3d, Ni 3p and Ni 2p lines in the course of ion sputtering and their dependences on take-off angle of photoelectrons were measured. The post-oxidation surface composition was: Ni (NiO) in the uppermost layer, its content increased with the time of heating. The following layer was enriched with ZrO2. The minimum of Ni/Zr atomic ratio was observed for 10–40 A depth, depending on intermetallic compound composition and heating time. The next layer was enriched with Ni and for 1000–1600 A depth the stoichiometric bulk composition was attained. The formation of a Ni rich layer over ZrO2 is explained by Ni diffusion through the oxide film.