Diffusion of hydrogen and oxygen in the high temperature proton conductor srceo3 investigated by dynamic conductivity measurements

In SrCeO₃ the oxygen vacancy concentration at elevated temperatures depends on the oxygen partial pressure in the surrounding atmosphere. Changes of the oxygen vacancy concentration are accompanied by change in the hole concentration and therefore can be measured by electrical conductivity measurements. We apply a dynamic method for studying the diffusion of oxygen vacancies by measurements of the time dependence of the electrical conduction after a sudden change in the oxygen partial pressure has taken place.

In doped samples and under wet conditions the protonic charge carriers are mainly incorporated by a dissociative absorption of water and lead to a noticeable protonic conduction. The proton diffusion in SrCe_0.95 Y_0.05O₃ is determined by relaxation measurements at a polarised sample in wet and hydrogen containing atmosphere. The electrochemical cell discussed here is characterised by a combination of one reversible and one (hydrogen) ion blocking electrode. From the time dependence of the depolarisation process the hydrogen diffusivity is extracted.