Using different wet-ceramic processes and ceramic membrane technology we have prepared various thin or thick ceramic membrane materials. The thin film ceramic membranes, prepared using the gel-solution process, have different material characteristics compared with the hulk materials, for example, higher ionic conductivity in the film plane than in the perpendicular direction. A very sensitive humidity dependence of the conductivity has been observed in the thin film ceramic membranes. Therefore, these membrane materials have a potential use for constructing new types of proton conducting electrolyte fuel cells and hydrogen or humidity sensors.