title: Atomic structure and composition of the yttria-stabilized zirconia (111) surface.
abstract: Anomalous and nonanomalous surface X-ray diffraction is used to investigate the atomic structure and composition of the yttria-stabilized zirconia (YSZ)(111) surface. By simulation it is shown that the method is sensitive to Y surface segregation, but that the data must contain high enough Fourier components in order to distinguish between different models describing Y/Zr disorder. Data were collected at room temperature after two different annealing procedures. First by applying oxidative conditions at 10- 5mbar O2and 700 K to the as-received samples, where we find that about 30% of the surface is covered by oxide islands, which are depleted in Y as compared with the bulk. After annealing in ultrahigh vacuum at 1270 K the island morphology of the surface remains unchanged but the islands and the first near surface layer get significantly enriched in Y. Furthermore, the observation of Zr and oxygen vacancies implies the formation of a porous surface region. Our findings have important implications for the use of YSZ as solid oxide fuel cell electrode material where yttrium atoms and zirconium vacancies can act as reactive centers, as well as for the use of YSZ as substrate material for thin film and nanoparticle growth where defects control the nucleation process.
authors.affiliation: Radboud University Nijmegen, Institute for Molecules and Materials, NL-6525AJ Nijmegen, The Netherlands ; Max Planck Institute for Intelligent Systems (former Max Planck Institute for Metals Research), D-70569 Stuttgart, Germany ; Deutsches Elektronen-Synchrotron (DESY), D-22607 Hamburg, Germany.
authors.forename: Vedran
authors.initials: V
authors.lastname: Vonk
authors.forename: Navid
authors.initials: N
authors.lastname: Khorshidi
authors.forename: Andreas
authors.initials: A
authors.lastname: Stierle
authors.forename: Helmut
authors.initials: H
authors.lastname: Dosch
keywords: Cubic YSZ; Oxide surfaces; SOFC; Solid-oxide fuel cell; Surface structure; Yttria stabilized zirconia