Anion-excess Bixbyite Gd2Ce2O7: Effect of Radiation on Anion Sublattice
Résumé
Structural changes produced by irradiation have been extensively studied in compounds derived from the parent fluorite structure where cations are initially ordered and in systems where both sub-lattices do not display long-range order. The irradiation behaviour of fluorite-related oxide systems where the cations are randomly distributed but the anions are highly ordered is not quantitatively explored yet. We report on a model system Gd2Ce2O7, with a randomly occupied cation sub-lattice while an ordered anion sublattice. This compound crystallizes in a new bixbyite-type symmetry where O vacancies order on half of the vacant sites of the ideal bixbyite structure. Swift heavy ion irradiation experiments and quantitative x-ray diffraction analysis were used to study the separate response of the anion sub-lattice to radiation. We show that the topological disorder on the anion sub-lattice grows faster than that on the cation sub-lattice. While a decrease in strain is observed as a function of fluence, the variance of the strain increases due to an increase of the microdomain wall density.
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