The chemical diffusion coefficient was determined, by using a conductivity relaxation technique, as a function of O partial pressures ranging from 10-15 to 1atm. This included an n/p mixed regime at 800 to 1100C. The chemical diffusivity varied convex-up, between 10-5 and 10-2cm2/s, at all temperatures. Its maximum fell at around the O partial pressure where the n-to-p transition occurred in stoichiometric material. This diffusion behavior was analyzed in terms of Wagner's theory of chemical diffusion, and the defect structure of the material. The measured total conductivity and chemical diffusivity, when combined, led to the estimation of defect-chemistry parameters without having to make any assumptions. This yielded the carrier mobilities and defect-equilibrium constants, and also offered some insight into the nature of the inherent acceptors in the undoped material.

Chemical Diffusivity and Defect Chemistry of BaTiO3. H.I.Yoo, C.R.Song: Electrochemistry, 2000, 68[6], 415-22. See also: Solid State Ionics, 1999, 124[3-4], 289-99