Time-of-flight secondary ion mass spectrometry as a tool for studying segregation phenomena at nickel–YSZ interfaces

Through a study of Ni–YSZ interfaces it is shown that time-of-flight-secondary ion mass spectrometry (TOF-SIMS) is a powerful and convenient tool for the analysis of ultra thin layers of segregated material at the interfaces and on free surfaces. Two different types of Ni, “pure Ni” (99.995% Ni) and “impure Ni” (99.8% Ni) were investigated. The contact areas on the YSZ and areas outside the contacts were examined with XPS and TOF-SIMS. The impure nickel causes a relatively larger amount of impurities to accumulate at the contact area, e.g. oxides of Mn, Ti, Si and Na. Some impurities migrate to the area outside the contact area. Even though on a larger scale the impurities seem to be homogeneously distributed, detailed analyses in and outside the contact area show the presence of impurity particles, and that the surface species are inhomogeneously distributed amongst the different grains. The extremely low detection limit, the small probe depth, the image capability, and the ease of elemental identification make TOF-SIMS an obvious choice as an analytical tool for studying segregation phenomena at metal–ceramic interfaces such as Ni–YSZ interfaces. XPS, being a quantitative technique, was used as a complementary technique to TOF-SIMS, which is not directly a quantitative technique.