Structural changes of Ce-Pr-O oxides in hydrogen:: a study by in situ X-ray diffraction and Raman spectroscopy

Ce-Pr-O mixed oxides prepared by coprecipitation and calcined at 1173 K reveal a non stoichiometric structure with oxygen vacancies in the bulk. In situ XRD and Raman spectroscopy were used to investigate these properties simultaneously and identified a thermal expansion coefficient twice as high as that of pure ceria at room temperature and the presence of a Raman band at 560 cm(-1), characteristic of the oxygen vacancies. These results confirm that praseodymium atoms are able to induce oxygen mobility in the bulk at 298 K. This is due to a structure containing a high number of anionic vacancies pre-existing at ambient temperature.