III International Conference

PP-II-62THE INFLUENCE OF SYNTHESIS PARAMETERS ON THE REAL/DEFECTSTRUCTURE OF PURE CERIA AND ZIRCONIAKuznetsova T., Sadykov V., Burgina E., Moroz E., Paukshtis E., Krivensov V.,Kochubey D., Kolomiichuk V., Fedotov M.Boreskov Institute of Catalysis SB RAS, Novosibirsk, RussiaE-mail: tgkuzn@catalysis.nsk.suEffects of the synthesis parameters (method of preparation, aging procedure etc.) on thereal/defect structure of pure ceria and zirconia samples prepared from cerium nitrate andzirconyl chloride were considered. Structural features of these oxides were characterized byXRD analysis, EXAFS, IR and Raman spectroscopy. SAXS and UV-Vis spectroscopy wereapplied to reveal defects.Dispersed pure ceria and zirconia attract a great attention as catalysts or supports formetal/oxide catalysts of red-ox/acid-base reactions as well as important components ofcomplex catalysts [1-2]. It is well known that synthesis procedures affect formation ofzirconia polymorphs (monoclinic, tetragonal or pseudocubic) while ceria retains a cubicfluorite structure for all preparation methods [1]. In this work combination of methods (XRD,EXAFS, IR and Raman spectroscopy, SAXS and UV-Vis spectroscopy) was applied toelucidate structural features (including defects) of pure oxides prepared from available ceriumnitrate and zirconyl chloride salts. For traditional precipitation route, effect of pH andtemperature of precipitation and/or aging, UV irradiation of precipitates on the real structurewas considered. For the polymerized complex method (based upon formation of the chelatecomplexes of metal cations and complex esters) the ratio of reagents was systematicallyvaried.For nanocrystalline ceria, defects appear to be mainly located in vicinity of domainboundaries. For samples prepared via polymerized complex method, these boundaries couldretain the structural features of nonstochiometric Ce n O m oxides characterized by different Ce-O distances with residual amount of Ce 3+ cations.The genesis of zirconias real structure prepared via precipitation route dependsconsiderably on the parameters of synthesis due to structural flexibility of freshly precipitatedamorphous zirconium hydroxide. A short -time UV irradiation was found to favor formationof the monoclinic phase at rather low temperatures, perhaps, via affecting bonding ofhydroxyls and /or water miolecules in the coordination sphere of Zr cations in tetramericZr 4 (OH) n (H 2 O) z+ m complexes in an amorphous hydroxide. Prolonged aging of the amorphous276