Raman spectroscopic study on the structure in the surface and the bulk shell of [Ce.sub.x][Pr.sub.1-x][O.sub.2-delta] mixed oxides

The difference between the surface and the bulk shell of [Ce.sub.x][Pr.sub.1-x][O.sub.2-delta] mixed oxides is studied by Raman spectroscopy with four different excitation lasers. The results have shown that the surface region and the bulk shell are different and the thickness of the surface layer with rich Pr increases with the decrease in the Ce content.