Surface characterization for high purity Fe-Cr alloys

Fe-50mass%Cr was prepared in a cold crucible fumace with induction heating, then refined by floating-zone melting (FZM). The chemistries on the surface before and after FZM were compared by XPS measurement. C and O were observed on top surfaces both before and after as a hydrocarbon, carbonyl group and carboxyl group which are adsorbed chemical components. The other impurities were observed on the surface in both cases ; however, the number and level of impurities on the surface after FZM were much larger than those on the surface before FZM ; these adhered to the surface during sample preparation for XPS measurement. It is concluded that sample preparation introduces contamination which affects the detection limit of chemical analytical instruments. Sn was only observed on the top surface after FZM. It was segregated Sn which was contained in chromium as a starting material. It must be eliminated before starting. From XPS depth profiling results, it was concluded that 0.2 nm thickness of carbon such as hydrocarbon and organic components are adsorbed on the 1 nm thickness of oxide layer. Below the oxide layer, a lack of Cr was observed down to a depth of 6 nm.