The surface of the perovskites LiBaF3 and BaZrO3 studied by low-energy ion scattering

Low‐energy ion scattering has been performed on the normal perovskite BaZrO3 and the only known inverse perovskite LiBaF3. BaO2, ZrO2, and BaF2 were used to quantify the surface coverage of the different constituents. In BaZrO3 the surface coverage showed an enrichment of Ba. Calibration to the metaloxides gave surface coverages of 80% and 20% for Ba and Zr, respectively. For the LiBaF3, also a higher Ba coverage was detected, and, compared to BaF2, found to be 75%. The enrichment of this twelvefold coordinated cation can be explained in terms of a segregation effect due to a lower surface free energy of the bariumoxide and ‐fluoride with respect to the zirconiumoxide or lithiumfluoride. In view of our earlier experiments on spinel structures, preferential exposure of certain planes of the perovskite structure is another possibility, which has yet to be evaluated. The results indicate that a surface terminated by cations in the B‐site, in most cases transition metals, does not present a reliable model when discussing the catalytic activity of the perovskites