Cerium – Oxygen – Zirconium

Structural Changes in Ce0.5Zr0.5O2−δ under Temperature-Swing and Isothermal Solar Thermochemical Looping Conditions Determined by in Situ Ce K and Zr K Edge X-ray Absorption Spectroscopy

“…Isothermal section of Ce (1– x ) Zr x O 2−δ system at 1773 K reproduced from Lebrun and Perrot . The dashed red line indicates Ce 0.5 Zr 0.5 O 2−δ for all compositions 0 ≤ δ ≤ 0.25.…”

“…While pure ceria maintains its fluorite-type structure over a large temperature range and up to very high nonstoichiometric δ, the substitution of ceria by zirconia leads to the formation of other phases. Most of them are closely related to and can be deduced from the fluorite-type structure . Allotropic phases in the ceria–zirconia system are essentially distorted fluorite-type phases, the most prominent being the tetragonal (space group P 4 2 / nmc ) t, t′, and t″ phases.…”

“…Additional reflections in the diffraction pattern indicate cation ordering in the κ-Ce 2 Zr 2 O 8 superstructure. The large variability in the amount of oxygen in the Ce–Zr–O system leads to nonstoichiometric structures with positive and negative deviations from the oxygen content of model crystallographic structures . In practice, the oxygen exchange properties of ceria–zirconia materials depend strongly on the preparation method and on their thermochemical history .…”