Chemical diffusivity in 1.8mol%Al-doped single crystals was measured, using conductivity relaxation techniques, as a function of ambient O partial pressures ranging from 10-18 to 1atm; at 800 to 1100C. As in the case of polycrystalline undoped material, the chemical diffusivity exhibited a maximum, of thermodynamic origin, at around the stoichiometric composition. The measured diffusivity was analyzed on the basis of the proposed defect structure, and Wagner's chemical diffusion theory. The mobilities of the electrons and holes, as well as all of the relevant defect-equilibrium constants, were then evaluated without making any prior assumptions.

Chemical Diffusivity of BaTiO3. C.Song, H.You: Journal of the American Ceramic Society, 2000, 83[4], 773-9