Sol-gel synthesis of tunable cerium titanate materials

Cerium titanate structures present a high technological interest because of their optical and catalytic properties. This work reports the synthesis of these materials by a sol--gel methodology that allows mixed oxides with Ti-IV/Ce-III, Ti-IV/ Ce-IV or Ti-IV/Ce-III-Ce-IV species to be obtained. Crystallization of CeO2-TiO2 mixed oxides and Ce2Ti2O7 pyrochlore phase was corroborated by XRD and Raman spectroscopy. Magnetic and EPR measurements were performed in order to clarify the oxidation state of the cerium ions in the system as a result of the easy oxidation of Ce-III. The firing atmosphere is crucial for the Ce-III/Ce-IV ratio, which is responsible for the different structure, but it also affects the colouration (yellow, green, brown). This methodology offers the possibility to modulate the Ce3+/Ce4+ content and particle sizes providing more ecological coloured pigments based on rare earth elements that could be interesting materials for advanced applications in catalysis. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).