High-resolution transmission electron microscopy studies of structural modifications in pd-al₂o₃interfaces

High-resolution transmission electron microscopy (HRTEM), in conjunction with extensive image simulation, has been applied to topotaxial Al2O3-Pd interfaces formed by the internal oxidation of Pd-Al alloys. The Al2O3 phase has been characterized as η-Al2O3 from HRTEM images. We conclude that the Al2O3 is terminated by O ions after oxidation and by Al ions after a subsequent annealing in Al vapour. This structural modification is consistent with earlier H-trapping experiments. The origin of the ceramic precipitates in relation to the transmission electron microscopy and complementary X-ray measurements and the difficulties of applying HRTEM to an incoherent topotaxial interface are discussed.