Observations of chromium-oxide films containing cerium and yttrium using transmission electron microscopy

Samples of a pure Fe-26%Cr alloy were sputter-coated with a 4-nm layer of CeO₂ or Y₂O₃, then oxidized at 900°C in 5×10^–3 torr of oxygen. The oxide scale was removed from the substrate by dissolution of the alloy substrate in a solution of iodine in anhydrous methanol and examined in, a transmission electron microscope to determine the microstructure of the oxide and the phases present in the scale. the phases CeCrO₃ (space group 62,Pnma and space group 221, ), YCrO₃ (space group 62,Pnma), and Y₂O₃ (space group 164, ) were found in the oxide scale in the initial stages of oxidation. The relevance of these species in the reactive-element effect is discussed.