It was pointed out that many O-deficient oxide perovskites were O-ion conductors in a dry environment. However, in humid atmospheres, they absorbed water which filled up O vacancies, released quasi-free protons into the structure and thus became proton conductors. The absorption of water required the transport of both protons and O ions. This effectively led to the transport of H2O under its chemical potential gradient. Relationships were deduced here between the chemical diffusion coefficient of H2O and the diffusion coefficients of protons and O vacancies. Emphasis was placed on the role of solution thermodynamics.

Chemical Diffusion Coefficient of H2O in AB(1-x)B'xO(3-x/2)-Type Perovskites. A.V.Virkar, H.D.Baek: Journal of the American Ceramic Society, 2002, 85[12], 3059-64