The diffusion of O in this perovskite-related non-stoichiometric oxide was investigated  in situ  by using thin films and high-temperature resistometry. Apart from a step change in the vicinity of the orthorhombic-tetragonal transition, the diffusivity exhibited a concentration-dependence for O stoichiometry deviations ranging from 0.3 to 0.8. The activation energy was constant (1.2eV) over the whole interval. It was proposed that O diffusion occurred via a vacancy mechanism which involved the O atoms at the extremes of the -O-Cu-O- chains in the basal plane.

V.Dediu, F.C.Matacotta: Physical Review B, 1998, 57[13], 7514-7