Local structure and nanoscale homogeneity of CeO2–ZrO2: differences and similarities to parent oxides revealed by luminescence with temporal and spectral resolution

Although homogeneity at the atomic level of CeO2–ZrO2 with a Ce/Zr atomic ratio close to unity is considered to be one of the main causes for the increased total oxygen storage capacity (OSC), the characterization approaches of homogeneity remain a major challenge. We propose a simple, yet effective method, to assess both structural and compositional homogeneity of CeO2–ZrO2 by using Eu3+ luminescence measured with time and dual spectral resolution (emission and excitation). For Eu3+–CeO2–ZrO2 calcined at 750 °C, the X-ray diffraction, Raman and High-Resolution Transmission Electron Microscopy data converge to a single pseudo-cubic phase. However, the evolution of Eu3+-delayed luminescence from cubic ceria-like to tetragonal zirconia-like emission reveals the formation of CeO2- and ZrO2-rich nanodomains and provides evidence for early phase separation. For Eu3+–CeO2–ZrO2 calcined at 1000 °C, the emission of Eu3+ reveals both structural and compositional inhomogeneity. Our study identifies the differences between the local structure properties of CeO2 and ZrO2 parent oxides and CeO2–ZrO2 mixed oxide, also confirming the special chemical environment of the oxygen atoms in the mixed oxide as reported earlier by Extended X-ray Absorption Fine Structure investigations.