The processes of O in-diffusion in c-textured epitaxial thin films were monitored by means of in situ electrical resistivity measurements. The chemical diffusion coefficients were found to be sensitive to the O content, and varied greatly upon crossing the phase transition point. The variation in diffusivity could be divided into 3 ranges, within which different diffusion mechanisms operated. The diffusivity was concentration-independent between the orthorhombic phase limits (interstitial mechanism), decreased as the O deficiency increased up to the point of the O-T phase transition, and then increased with increasing O deficiency in the tetragonal phase (vacancy mechanism). The activation energies for O diffusion were deduced to be about 0.97 and 0.91eV in the tetragonal and orthorhombic phases, respectively.

Diffusion Mechanism of Oxygen in Orthorhombic and Tetragonal c-Textured Epitaxial YBa2Cu3O7-δ Thin Films. C.Zhen, L.Li, Z.Wang: Superconductor Science and Technology, 1999, 12[3], 158-61