Self-diffusion and conductivity were measured in cubic monocrystals which were doped with 9.5mol%Y2O3. The O diffusion coefficients were deduced from profiles which were obtained by gas/solid 18O/16O isotopic exchange. Two volume diffusion mechanisms were detected. One of these was a fast O diffusion process which was noted here for the first time. It could be described by:

D(cm2/s) = 0.654 exp[-119(kJ/mol)/RT]

at temperatures of between 310 and 1100C. There was also a slow O diffusion process for which the O diffusion coefficients were similar to those previously published. The slow process could be described by:

D(cm2/s) = 3.77 x 10-4exp[-78(kJ/mol)/RT]

at temperatures of between 500 and 1100C. In this system, the majority defects were O vacancies which compensated the charge deficiency that was introduced by Y. Connected micro-domains which contained complex defects (with association between VOoo and YZr’) appeared to be responsible for the faster diffusion (but higher activation enthalpy). The slower diffusion (but lower activation enthalpy) was explained in terms of free O vacancy migration in the disordered crystal. It was concluded that complex defects, (VOoo+YZr’)o, played an important role at the lowest temperatures. Changes in the yttria content modified the point defect concentrations and interactions, and strongly affected the ionic transport properties.

H.Solmon, C.Monty, M.Filal, G.Petot-Ervas, C.Petot: Solid State Phenomena, 1995, 41, 103-12