XANES Studies of Si and Zr in Composite Hollow Spheres

ANDRINI L.; ARNAL, P.M.; REQUEJO F.G.

Brasil

Congreso; RAU; 2009

Zirconia is an extremely important material with wide-ranging applications includ-ing as a high-performance transformation-toughened structural engineering ceramicand as a solid electrolyte, and has also found application as a catalyst and catalystsupport, especially when durability to chemical attack is required [1].    The Zr L2-L3 and Si K-edges XANES measurements were carried out at D04A-SXS beamline at LNLS. The preparation of nanocrystalline zirconia and hollowsspheres (@ZrO2 ) were already reported elsewhere [2].    In this work we report a XANES study of Zr and Si present in @ZrO2 to obtaininformation about the electronic and local morphological structure of Zr and Si.These hollow spheres are made of nanometer-sized zirconia domains surrounded atleast partially by a Si-containing material. A pore structure extends from the innersurface, which defines the inner macropore, to the external surface of the spheres,allowing mater diffusion across the shell [3].    According to white line (WL) intensity and the feature of the Si K-edge ab-sorption spectra, the Si atoms in @ZrO2 samples have similar neighborhood thatSi in SiO2 and they are not forming ZrSiO4 . The evaluation of the splitting at theWL of the Zr L2,3 XANES spectra of the samples indicates that, for low treat-ments temperatures (293 K), the local environment of Zr is similar to ZrO2 , andfor temperatures higher than 973 K, the phase of Zr in @ZrO2 samples is similarto BaZrO3 , where Zr is octahedrally coordinated.