AVS 52nd International Symposium
    Nanometer-Scale Science and Technology Tuesday Sessions
       Session NS-TuP

Paper NS-TuP13
Oxide Electrolyte Nanostructures for Low Temperature SOFC Operation

Tuesday, November 1, 2005, 4:00 pm, Room Exhibit Hall C&D

Session: Nanometer Scale Science and Technology Poster Session
Presenter: S. Thevuthasan, Pacific Northwest National Laboratory
Authors: S. Thevuthasan, Pacific Northwest National Laboratory
L. Saraf, Pacific Northwest National Laboratory
V. Shutthanandan, Pacific Northwest National Laboratory
O.A. Marina, Pacific Northwest National Laboratory
C.M. Wang, Pacific Northwest National Laboratory
S. Azad, Pacific Northwest National Laboratory
Y. Zhang, Pacific Northwest National Laboratory
A. El-Azab, Pacific Northwest National Laboratory
Correspondent: Click to Email
Development of electrolyte materials that possess high oxygen ion conductance at relatively low temperatures is essential to improve the performance of electrochemical devices. Ceria, doped with a divalent or trivalent cation, exhibits higher ion conductance compared with yittria-stabilized zirconia, the electrolyte currently used in solid oxide fuel cells. In this research, we have investigated layer by layer structures of highly oriented gadolinia doped ceria and zirconia in order to determine the nanoscale effects on the ion conductance. Highly oriented multilayered nanostructures of gadolinia-doped ceria and zirconia with interfaces parallel and perpendicular to the substrate surfaces were grown on sapphire substrates using molecular beam epitaxy and glancing angle sputter deposition, respectively. These structures were characterized by several bulk and surface sensitive characterization techniques. At relatively low temperatures, the oxygen ion conductance in highly oriented layered structures was found to increase with increasing number of layers in the films with interfaces parallel to the substrate surfaces. Theoretical calculations were also performed to understand the effects of space charge regions induced by the thermodynamic equilibrium and impurity segregation as well as the influence of the grain microstructures on the electric transport processes in these materials. In addition, labeled oxygen diffusion measurements were carried out by 18O(p,alpha)15N nuclear reaction analysis (NRA) and the diffusivity correlation is established with ionic transport by measuring the oxygen ionic conductivity using impedance spectroscopy. These results will be discussed along with the results from stability tests of these layered structures at elevated temperatures.