We propose a new method for the synthesis of perovskite materials with high ion (proton and oxygen) conductivity for various applications in low temperature Ceramic-based Fuel Cells for use in the US Hydrogen Economy. Oxide-based fuel cells operate at high temperatures with advantages that include high efficiency, flexible fuel types, and inexpensive non-noble catalysts. Conversely, high temperatures lead to component breakdown and large size heating units.  A major materials breakthrough is needed in this technology to lower the operating temperatures (to 500-600°C) while retaining high catalytic and diffusion activity, to use a variety of fuel sources (H₂ and carbon-based), and produce high surface area phases (maximized ionic diffusion and component/gas interfaces).

This project proposal focuses on the synthesis and characterization of “tunable” perovskite ceramics with resulting controlled strength and temperature of dielectric constants and/or with ionic conductivity.  Traditional methods of synthesis involve high temperature oxide mixing and baking.  We are using a new methodology of synthesis involving the (1) low temperature hydrothermal synthesis of metastable porous phases with “tuned” stoichiometry, and element types, and then (2) low temperature heat treatment to build exact stoichiometry perovksites, with the desired vacancy concentrations.  This flexible pathway can lead to compositions and structures not attainable by conventional methods.  These materials will then be studied by high temperature oxide melt solution calorimetry and conductivity measurements to better delineate stability and stoichiometry/bulk conductivity relationships.  This in turn will lead to a predictive model for the possible extent of (sometimes metastable) substitutions.

Team: Tina Nenoff, Emily Michaels, Ron Loehman, Chris Cornelius; Alexandra Navrotsky (UCDavis)

Funding: LDRD FY04-06