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

摘要

The chemomechanical properties and microstructural stability of nanocrystalline Pr_xCe_(1 - x)O_(2 - δ) solid solutions are studied as a function of temperature by in situ X-ray diffraction measurements under oxidizing conditions at P(O_2) ~ 200 mbar. The chemical expansion coefficient of nanocrystalline powder specimens, operative at intermediate temperatures during which Pr~(4+) is reduced to Pr ~(3+), is found to be similar to that obtained for coarse-grained Pr_xCe_(1 - x)O_(2 -)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 PrxCe_(1 - x)O_(2 - δ) is highly oxygen deficient, was found to be greater than that measured for fully oxidized Pr _xCe_(1 - x)O_(2 - δ), with potential sources of these changes discussed. Moreover, the microstructure of nanocrystalline P_rxCe_(1 - x)O_(2 - 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.