The O self-diffusion coefficients were determined for polycrystalline microspheres by using an isotope exchange technique with 18O as the tracer. The diffusion coefficients for 1099 to 1644C could be described by:

D (cm2/s) = 5.67 x 10-3 exp[−219(kJ/mol)/RT]

The results were an order of magnitude smaller than those reported for monocrystalline ThO2, while the activation energy was similar to that for single crystals.

K.Ando, Y.Oishi, T.Tsuji, Y.Hidaka, K.Shiba: Journal of Nuclear Materials, 1984, 120[1], 99-101