Chemomechanical properties and microstructural stability of nanocrystalline Pr-doped ceria: An in situ X-ray diffraction investigation

The chemomechanical properties and microstructural stability of nanocrystalline PrxCe1 − xO2 − δ solid solutions are studied as a function of temperature by in situ X-ray diffraction measurements under oxidizing conditions at P(O2) ~ 200 mbar. The chemical expansion coefficient of nanocrystalline powder specimens, operative at intermediate temperatures during which Pr4+ is reduced to Pr3+, is found to be similar to that obtained for coarse-grained PrxCe1 − xO2 − δ. This is contrary to reports regarding variation of physical and chemical properties with crystallite size. The thermal expansion coefficient, measured under conditions for which PrxCe1 − xO2 − δ is highly oxygen deficient, was found to be greater than that measured for fully oxidized PrxCe1 − xO2 − δ, with potential sources of these changes discussed. Moreover, the microstructure of nanocrystalline PrxCe1 − xO2 − δ is observed to have excellent stability at working temperatures below 800 °C, enabled by the inherent microstrain in the structure, highlighting the potential application of this material for solid state electrochemical devices.

Research highlights
► The chemomechanical properties of PrxCe1 − xO2 − δ (PCO) were studied by in-situ XRD.
► The properties of nanocrystalline and coarse-grained PCO were similar.
► The thermal expansion showed different characteristics below 400 and above 1000 °C.
► The microstructure of the nanocrystalline powders was stable up to 800 °C in air.