화학공학소재연구정보센터
Journal of the American Ceramic Society, Vol.90, No.4, 1208-1214, 2007
Oxygen non-stoichiometry and thermal-chemical expansion of Ce0.8Y0.2O1.9-delta electrolytes by neutron diffraction
A dense tubular solid electrolyte with the composition Ce0.8Y0.2O1.9-delta (CY20) was prepared. In situ time-of-flight neutron powder diffraction (TOF-ND) was performed at 900 degrees C in the oxygen partial pressure pO(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 pO(2) in the range of pO(2)> 10(-14) atm, while a dramatic expansion (similar to 0.6%) of the fluorite structure occurred at a pO(2) of 10(-18) atm. By refining all reasonable structural parameters, an approximately linear relationship between lattice parameter and oxygen vacancy delta was observed, resulting in epsilon(c)/delta=0.08 and corresponding to delta=0.10 at a pO(2) of 10(-18) atm, all in agreement with the data published in the literature. The relative change in lattice parameter Delta a/a followed a -1/4 power relation with pO(2) in a low-pO(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.