The results of γ-γ angular correlation experiments performed on the 181Ta nucleus in calcia-and yttria-stabilized zirconias between 20 and 1150C are 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 required an activation energy of 0.91eV in calcia-stabilized material, and an energy of 0.82eV in yttria-stabilized material. 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. The 181Ta relaxation data, especially a comparison of the data relative to aged and de-aged calcia-stabilized zirconia, strongly suggested the existence of short-range ordering phenomena in these solid solutions.

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