A dense tubular solid electrolyte with the composition Ce0.8Y0.2O1.9− (CY20) was prepared. In situ time-of-flight neutron powder diffraction (TOF-ND) was performed at 900°C in the oxygen partial pressure pO2 range from 10−1–10−18 atm, and TOF-ND data were analyzed by the Rietveld method. Diffraction data showed that the lattice parameter moderately increased with decreasing pO2 in the range of pO2>10−14 atm, while a dramatic expansion (∼0.6%) of the fluorite structure occurred at a pO2 of 10−18 atm. By refining all reasonable structural parameters, an approximately linear relationship between lattice parameter and oxygen vacancy was observed, resulting in c/=0.08 and corresponding to =0.10 at a pO2 of 10−18 atm, all in agreement with the data published in the literature. The relative change in lattice parameter Δa/a followed a −1/4 power relation with pO2 in a low-pO2 regime. As several (often strongly correlated) structural parameters can affect the intensities in ND profiles, care was taken to select refinement variables. It was found that O atom thermal factors for CY20 increased as the oxygen vacancy concentration and lattice expansion increased.
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Document Type: Research Article
Intense Pulsed Neutron Source Division, Argonne National Laboratory, Argonne, Illinois 60439
Energy Technology Division, Argonne National Laboratory, Argonne, Illinois 60439
Publication date: April 1, 2007