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Oxygen Non‐Stoichiometry and Thermal–Chemical Expansion of Ce 0.8 Y 0.2 O 1.9−δ Electrolytes by Neutron Diffraction
Author(s) -
Li Yaping,
Maxey Evan R.,
Richardson James W.,
Ma Beihai,
Lee Tae H.,
Song SunJu
Publication year - 2007
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2007.01606.x
Subject(s) - neutron diffraction , thermal expansion , rietveld refinement , lattice constant , stoichiometry , oxygen , analytical chemistry (journal) , lattice (music) , materials science , fluorite , diffraction , x ray crystallography , powder diffraction , chemistry , crystallography , crystal structure , physics , organic chemistry , chromatography , acoustics , optics , metallurgy
A dense tubular solid electrolyte with the composition Ce 0.8 Y 0.2 O 1.9−δ (CY20) was prepared. In situ time‐of‐flight neutron powder diffraction (TOF‐ND) was performed at 900°C in the oxygen partial pressure p O 2 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 p O 2 in the range of p O 2 >10 −14 atm, while a dramatic expansion (∼0.6%) of the fluorite structure occurred at a p O 2 of 10 −18 atm. By refining all reasonable structural parameters, an approximately linear relationship between lattice parameter and oxygen vacancy δ was observed, resulting in ɛ c /δ=0.08 and corresponding to δ=0.10 at a p O 2 of 10 −18 atm, all in agreement with the data published in the literature. The relative change in lattice parameter Δ a / a followed a −1/4 power relation with p O 2 in a low‐ p O 2 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.