Sol–Gel Synthesis of Tunable Cerium Titanate Materials

Abstract

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.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)