| Techniques and methodologies developed to reproducibly prepare and characterize yttria stabilized zirconia (YSZ) for use as a model catalyst support are presented. Analysis of a large number of YSZ(100) single crystals are examined by ambient atomic force microscopy (AFM), and x-ray photoelectron spectroscopy (XPS), in order to understand sources of variability and irreproducibility in the YSZ literature. The knowledge gained by ambient studies is then utilized to guide development of instrumentation and techniques to characterize YSZ under ultrahigh vacuum, and to prepare the (100) surface for self-consistent model catalyst studies.;In-situ UHV scanning tunneling microscopy (STM) is used for the first time to study the surface of a bulk YSZ single crystal, images are presented in combination with XPS results. These techniques are used to characterize surface impurities and their interaction with YSZ. Cationic impurities are shown to accumulate at the upper surface region, but can be removed by heating to approximately 450°C, whereas silicon requires heating to at least 900°C. Carbon is found to react with YSZ(100) in complicated ways. Initial defect structure, in the form of oxygen vacancies and solubilized/surface carbon, can provide the conditions at elevated temperature to allow the reduction of zirconia to zirconium carbide. This carbide may be removed, along with the specific defect structure that provides the pathway for carbide formation, through thermal oxidation. STM shows that the clean and stoichiometric YSZ(100) surface may reconstruct under tip induced or thermally reductive conditions to form large clusters. With the removal of kinetic hindrance through heat, the clusters can self organize in a manner similar to that observed in ambient conditions.;In ambient conditions the complex interaction of impurities and defects are demonstrated to produce an inhomogeneous defect layer composed of stoichiometric and oxygen deficient regions. Introduction of oxygen vacancies modifies the lattice constant of YSZ, causing it to dewet and self organize at high temperature. Furthermore, stoichiometric and defective surface regions are shown to interact with metal deposited through e-beam evaporation in vastly different manners. Therefore variation in the defect layer can produce large dispersion in deposited metal location and dimension. |
