The addition of Ce4+ has a significant effect on the temperatures for conversion of gels into anatase and anatase into rutile, and depresses the growth of anatase crystal. It is suggested that Ce4+ addition helps to prepare ultrafine anatase crystals and enhance the thermal stability of anatase.

Oxygen storage capacity (OSC) is an important parameter in three-way-catalysts (TWCs) for the purification of exhausts from gasoline engines of automobiles. Beciuse CeO2 possesses the unique performance, it is added into catalytic coatings of converters to adjust the oxygen concentration of the exhausts. However, small amounts of CeO2 existing in the coating is insufficient in this when air-fuel ratio fluctuates in a relatively wide range. In the present work, a kind of cordierite-CeO2 ceramic was prepared through solgel method so as to append the OSC to the support on which the catalyst is coated. Advanced measurement techniques such as XRD, SEM and gas chromatograph were employed to evaluate the microstructure and properties of the composite ceramics. Results show that the composite ceramics consist both phases of cordierite and CeO2. CeO2 particles are uniformly and separately distributed in the cordierite matrix, their number and granularity dependent on the amount of Ce4+ addition. The cordierite and 10 wt.% CeO2, possesses an apparent OSC, appropriate porosity, flexural strength and thermal expansion coefficient. It will be helpful to enhance the OSC of the catalytic converters and so improve the purification effects to the exhausts.

Stable oxygen concentration in exhausts is a decisive factor in catalytic purification of the vehicle exhausts. Nanostructured CeO2 is generally added into catalytic coating on a ceramic support to adjust the oxygen concentration because it possesses a unique oxygen storage capacity (OSC). However, a small amount of CeO2 gets insufficient when the oxygen concentration fluctuates in a large range. In the present work, the cordierite-CeO2 composite ceramic with oxygen storage capacity was prepared for a support material of catalytic converters. The oxygen storage-release performance of the ceramics, including temperature of releasing oxygen, adsorption process of oxygen and the oxygen storage, was examined by a temperature-programmed gas chromatography. The composition of the ceramics was analyzed by an X-ray powder diffraction (XRD) and a scanning electron microscope (SEM) to validate the reliability of the ceramic as the support material with OSC. Results show that the ceramics consist of α-cordierite and CeO2 phases, the latter of which is uniformly dispersed throughout the cordierite matrix. The ceramic powder with 10-20wt% of CeO2 possesses the expected oxygen storage capacity. It is suggested that this novel cordierite-CeO2 composite ceramic is helpful of improving the purification effect of vehicle exhausts.