Chemical diffusivity in undoped polycrystalline material was studied by using a conductivity relaxation technique, at temperatures of 800 to 1100C, as a function of ambient O partial pressures ranging from 10-16 to 1atm. This spanned an n-type to p-type transition regime. A mathematical method was developed in order to convert the conductivity relaxation to the corresponding non-stoichiometry relaxation in the transition regime. It was found that the chemical diffusivity appeared to exhibit a maximum at the n-to-p transition point where the electronic minimum conductivity fell. The surface reaction became more rate-determining than diffusion as the transition point was approached from either the n-type or the p-type side.

Chemical Diffusivity of BaTiO3 - I: Experimental Determination. C.R.Song, H.I.Yoo: Solid State Ionics, 1999, 120[1-4], 141-53