The electrical conductivity and chemical diffusion coefficient of Sr-doped samples were measured as a function of the O partial pressure and temperature. It was found that, at high partial pressures, the electrical conductivity was independent of the partial pressure and was proportional to the Sr content. At low partial pressures, the conductivity decreased exponentially with decreasing partial pressure. The pressure dependence was explained in terms of a simple point defect model in which SrLa’, CrCr• and VO•• were assumed to be the predominant species. The chemical diffusion coefficient was deduced from the time dependence of the electrical conductivity following a sudden change in the O partial pressure. Its value increased with decreasing O partial pressure. This was explained in terms of ambipolar diffusion theory and defect chemistry. The vacancy diffusion coefficient which was calculated from the measured chemical diffusion coefficient was independent of the vacancy concentration when the latter was not too high. It was therefore suggested that the vacancies were non-interactive and free.

I.Yasuda, M.Hishinuma: Solid State Ionics, 1995, 80[1-2], 141-50