A process for converting a carbon containing fuel and water vapor into a reformate gas that includes hydrogen, carbon monoxide and carbon dioxide, using water molecules that diffuse through a membrane by steam permeation reforming. The process includes providing a ceramic membrane comprising an oxide ceramic having intrinsic and extrinsic oxygen ion vacancies, and having first and second surfaces; where the oxide ceramic capable of reacting with gaseous water molecules at the first surface by the reversible reaction, H.sub.2O(g)+V.sub.O.sup..cndot..cndot.+O.sup.x.sub.O2OH.sup..cndot..sub.O- ; and the oxide ceramic capable of producing gaseous water molecules at the second surface by the reversible reaction, 2OH.sup..cndot..sub.OH.sub.2O(g)+V.sub.O.sup..cndot..cndot.+O.sup.x.sub.O- ; contacting water vapor with the first surface; contacting the reformate gas with the second surface, whereby solid state ambipolar diffusion of oxygen ion vacancies and protons across the membrane occurs; and the ambipolar diffusion produces a net diffusion flux of water molecules through the membrane from the first surface to the second surface.