A study was made of oxygen diffusion in non- and Nb2O5-doped Bi4Ti3O12 ceramics using two-dimensional isotope mapping. In non-doped Bi4Ti3O12, the grain boundary acted as a barrier to oxygen diffusion, reflecting the presence of a space charge layer at the grain boundary. In Nb2O5-doped Bi4Ti3O12, a textured morphology was found by bulk and grain-boundary diffusion of oxygen. Diffusion coefficients were determined from the individual grains and grain boundaries. The difference in diffusion paths resulted from the decrease in oxygen-defect concentration owing to the addition of Nb2O5. The bulk-diffusion coefficient along the ab-plane was about one order of magnitude larger than that in the direction of the c-axis. The grain-boundary-diffusion coefficients varied by about two orders of magnitude. The bulk and grain-boundary diffusion of oxygen depended significantly on the crystal orientation.

Effect of Dopant, Crystal Orientation, and Space Charge Layer on Oxygen Diffusion in Bi4Ti3O12 Ceramics. I.Sakaguchi, K.Matsumoto, H.Nagata, Y.Hiruma, H.Haneda, T.Takenaka: Japanese Journal of Applied Physics, 2010, 49[6], 061507