The results of γ-γ angular correlation experiments performed on the 181Ta nucleus in calcia-doped cerias between 20 and 1150C were reported. At high temperatures, the angular correlation spectra indicated a relaxation of the 181Ta spins induced by the diffusive motions of O vacancies. The latter motions required an activation energy of 0.50eV for a CaO content of 5mol%, and an energy of 0.56eV for a CaO content of 11.5mol%CaO. The slow and fast relaxation regimes were successively observed when the temperature was raised. The behaviour of the relaxation constant was fairly well reproduced by assuming the existence of fluctuations in the potential energy barrier which controlled the migration of O vacancies. The local investigation of O self-diffusion demonstrated the homogeneous behaviour of these highly defective oxides at the microscopic level.

181Ta Gamma-Gamma Angular Correlation Study of Oxygen Self-Diffusion in Heavily Defective Oxides. A.Baudry, P.Boyer, A.L.de Oliveira: Journal of Physics and Chemistry of Solids, 1982, 43[9], 871-80