Concentration dependence of oxygen diffusivity in GdBa 2 Cu 3 O 6 + y films

Oxygen diffusion in the perovskite-related nonstoichiometric oxide ${\mathrm{GdBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6+y}$ has been investigated in situ on thin films using high-temperature resistive measurements. Except for a step change in the vicinity of the orthorhombic-tetragonal structural transition, the diffusivity shows no concentration dependence over a wide interval $(0.3lyl0.8).$ The activation energy is constant in the whole measured interval ${(E}_{o}\ensuremath{\approx}1.2\mathrm{eV}).$ It is proposed that oxygen diffusion propagates via vacancy mechanism, involving the oxygen atoms at the extremes of the -O-Cu-O- chains in the basal plane.