Effect of Dopant, Crystal Orientation, and Space Charge Layer on Oxygen Diffusion in Bi4Ti3O12 Ceramics

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We studied oxygen diffusion in non- and Nb2O5-doped Bi4Ti3O12 (BIT) ceramics by two-dimensional isotope mapping. In non-doped BIT, 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 BIT, 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.
2010-06-25