Room temperature mobility and diffusion coefficient of oxygen in polycrystalline YBa₂Cu₃O_7-x

The practical diffusion coefficient of oxygen in YBa₂Cu₃O_7-x at room temperature, as measured by a current decay method in a wet electrochemical set-up was found to be 4 ± 2 × 10^-12 cm²/sec, essentially independent of grain size (in polycrystalline thin films or bulk pellet) and of surface properties. Therefore it is concluded that the rate-determining step in the diffusion process, the movement of the oxygen inside the grain, is much faster than what would be expected on the basis of extrapolation of high temperature data. This explains our ability to use RT reduction to form metastable 123 variants.