Influence of La precursors on structure and properties of CeO2-ZrO2-Al2O3 composite oxides

Three La-doped CeO2 -ZrO2-Al2O3 (CZA) composite oxide samples, namely, CZA-I, CZA-II and CZA-III, were prepared following a co-precipitation method in the presence of La2O3, La(NO3)(3).6H(2)O and H[La(EDTA)]center dot 16H(2)O precursors, respectively. When the precursor samples are sintered at 1000 degrees C, the as-prepared composite oxides mainly exhibit the CeO2-ZrO2 cubic fluorite phase, while the gamma-Al2O3 and delta-Al2O3 phases appear when the precursor samples are subjected to sintering at 1100 and 1200 degrees C. CZA-III exhibits improved redox properties after high-temperature treatment compared with CZA-I and CZA-II. CZA-III presents the largest surface area of 97.46 m(2)/g among the three CZAs when the CZA-III precursor sample is sintered at 1000 degrees C. Furthermore, the corresponding oxygen storage capacity (OSC) is the largest with value of 400.27 mu mol/g when CZA-III precursor sample is sintered at 1000 degrees C. Additionally, CZA-III exhibits the best thermal stability and the highest reduction temperature. However, by increasing the sintering temperature to 1200 degrees C, there is a dramatic decline in the properties of surface area and OSC. And a decrease for CZA-III in surface area by 58.94% and a decrease of the OSC value by 74.56% are observed.