Modeling of Material Parameters for Increased Steam-Permeation in Yttrium-Doped Barium Cerate Ceramic Membranes

Ceramic steam-permeation membranes permit high temperature transport or separation of water vapor and have the potential to significantly improve the efficiency of a variety of energy conversion technologies including solid oxide fuel cells, membrane reformers, and coal gasification. Though previously overlooked because it was believed that steam either could not be transported selectively or that transport rates would inevitably be far lower than O₂ transport membrane (OTM) alternatives, recent results indicate that steam-permeation membranes may be a compelling alternative to OTMs. In addition to high protonic conduction, yttrium- and gadolinium-doped barium cerate (BCY and BCG respectively) have also exhibited impressive steam-permeation capabilities under suitable conditions. Through analytical modeling of hydration thermodynamics and ambipolar diffusion kinetics, this paper examines the materials parameters that lead to increased steam-permeation, focusing in particular on BaCe_0.9Y_0.1O₃. The relationship between dehydration temperature and the temperature of maximum flux, as well as the effect of ionic diffusion activation energies on these quantities, are presented. Insight provided by these models provides directions for the future development as well as understanding of improved steam permeation materials and their possible deployment in fuel cell applications.