Synthesis and characterization of doped nano-sized ceria–zirconia solid solutions

Two compositions Ce0.50Zr0.39La0.04Y0.07O2−δ and Ce0.25Zr0.65La0.04Y0.06O2−δ based on ceria-zirconia solid solutions were prepared as nanopowders using a continuous hydrothermal flow synthesis reactor, followed by either freeze-drying or hotplate-drying of the slurry. Each dried nanopowder was then subjected to 10 h heat-treatment at 1000 °C, 1100 °C or 1200 °C in air (to simulate accelerated ageing). The reducibility and hydrogen consumption of the oxidised samples were measured using temperature programmed reduction (TPR) up to 1000 °C. The effects of composition, drying method and heat-treatment temperature were evaluated on the TPR profiles of the materials. The powders were further investigated using a range of analytical methods including UV/Vis spectroscopy (which yielded colour data), Raman spectroscopy, powder X-ray diffraction, BET surface area measurements and X-ray photoelectron spectroscopy (XPS). Chemometric methods were used to investigate relationships between the spectroscopic and total oxygen storage capacity (OSC) data. Principal component analysis (PCA) was used to provide a simple interpretation of the effects of various synthesis and treatment parameters on Raman spectra. Principal component regression (PCR) was used to build regression models relating the Raman spectra and the temperature of hydrogen consumption peak at several set temperatures in the TPR. The total hydrogen consumption of the materials was generally high, while the drying and heat-treatment conditions appeared to have a significant effect on the final properties of the resulting powders, such as the surface area and total oxygen storage capacity.