The non-stoichiometry of the oxide was determined by performing thermogravimetric measurements under controlled partial pressures of CO2/CO mixtures. The O potentials which corresponded to deviations of 0.02, 0.06 or 0.20 from stoichiometry were measured, using an electrolyte O sensor, under O partial pressures of between 10-14 and 10-3atm., at temperatures of between 1200 and 1500C. Defect equilibrium equations were derived, and the relationship between non-stoichiometry and O partial pressure was analyzed in terms of the mass action law. The predominant defect species in a given region were determined by fitting non-stoichiometry versus partial pressure data to each theoretical model. It was found that the calculated curves for (2:1:2)m’ and (Er’U•)x clusters in hyper-stoichiometric samples, and for the (2Er’VO••)decx cluster in hypo-stoichiometric samples, were in good agreement with the experimental results.

H.S.Kim, Y.K.Yoon, Y.W.Lee: Journal of Nuclear Materials, 1995, 226[1-2], 206-15