Tracer diffusion of oxygen in ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$

The tracer diffusion of ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ in ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ has been measured at temperatures from 300 to 850 °C at an oxygen partial pressure of 1×${10}^5$ Pa, and as a function of oxygen partial pressure at 600 °C. The diffusion of oxygen is strongly anisotropic. The faster component, associated with diffusion in the ab plane, has an activation energy of 0.97±0.03 eV. There is no break in the Arrhenius plot at the orthorhombic-tetragonal transformation temperature. The diffusion coefficient is not a strong function of oxygen partial pressure from 3×${10}^3$ to 1×${10}^5$ Pa at 600°C. The results are compared to the predictions of the various theories of diffusion in ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$.