A grain-boundary enhanced diffusion model was applied to cation interdiffusion in polycrystalline fluorite-cubic solid solutions in order to determine the lattice and grain-boundary interdiffusion coefficients separately. The Zr-Hf lattice interdiffusion, determined for the (Zr1−xHfx)O2-16CaO system at 1502 to 2083C, was described by:

D (cm2/s) = 2.3 x 10-2 exp[-90(kcal/mol)/RT]

while the grain-boundary interdiffusion was described by:

D (cm2/s) = 9.8 x 10-8 exp[-61(kcal/mol)/RT]

Cation Interdiffusion in Polycrystalline Fluorite-Cubic Solid Solutions. Y.Oishi, Y.Sakka, K.Ando: Journal of Nuclear Materials, 1981, 96[1-2], 23-8