TPR, XRD and XPS characterisation of ceria-based materials synthesized by freeze-drying precursor method

A freeze-drying precursor method was used to obtain submicrometric powders of ceria-based materials such as Ce1−xGdxO2−δ (x=0, 0.01, 0.05, 0.10 and 0.20), 80%CeO2–20%ZrO2, 80%CeO2–20%Al2O3 and (1−y)Ce0.99Gd0.01O2−δ– (y)Al2O3 (y=0.01, 0.02, 0.05, 0.10 and 0.30) at temperatures as low as 400 °C. The phase formation and evolution with the temperature was studied by X-ray diffraction (XRD). Also, temperature programmed reduction (TPR) was performed to investigate the reducibility of the ceramic powders. It was observed that after reduction of the ceria-based materials the fluorite structure of the samples was retained. The TPR profiles showed two peaks which are associated to the surface and bulk ceria reduction processes. Likewise, after the TPR measurements the resulting powders have showed high phase stability and reproducibility. XPS results confirmed the reduction of Ce4+ to (Ce3++Ce4+) ratio with alumina doping.