AVS 53rd International Symposium
    Applied Surface Science Tuesday Sessions
       Session AS+SS-TuM

Paper AS+SS-TuM6
Effects of Dopant Concentration and Microstrcutres on Ionic Conductivity in Samaria Doped Ceria Thin Films

Tuesday, November 14, 2006, 9:40 am, Room 2005

Session: Environmental Materials and X-ray Spectroscopies
Presenter: Z.Q. Yu, Nanjing Normal University
Authors: Z.Q. Yu, Nanjing Normal University
C.M. Wang, PNNL
M.H. Engelhard, PNNL
D.E. McCready, PNNL
V. Shutthanandan, PNNL
R. Shao, PNNL
P. Nachimuthu, UNLV
O. Marina, PNNL
I. Lyubinetsky, PNNL
L.V. Saraf, PNNL
S. Thevuthasan, PNNL
Correspondent: Click to Email
Recently, samaria doped ceria (SDC) have received much attention in the literature due to its high ionic conductivity and high oxygen ion transport, and they are considered to be the most promising solid electrolytes for the intermediate temperature solid oxide fuel cells (SOFCs). Although SDC materials show promising results, there are controversies regarding the dopant concentration that provide higher values for ionic conductivity. The discrepancies in ionic conductivity are mostly due to different sample preparation methods and the crystalline quality associated with these methods. In addition, high quality single crystal ceria thin film work with dopants is limited in the literature. In this study, we have investigated the ionic conductivity as a function of samarium dopant concentration in high quality samaria doped ceria films that were grown on sapphire (0001) substrates using oxygen plasma assisted molecular beam epitaxy (OPA-MBE). The structural properties of these films were characterized using insitu reflection high energy electron diffraction (RHEED) and exitu glancing angle x-ray diffraction. Thickness along with the compositional analysis was carried out using Rutherford backscattering spectrometry and x-ray photoelectron spectroscopy depth profiling. Microstructures in the films and at the interfaces were investigated by high resolution transmission electron microcopy (TEM) and TEM micrographs show sharp interfaces without grains and film/substrate epitaxial relationship as CeO@sub 2@ (111)// alpha-Al@sub 2@O@sub 3@ (0001) and CeO@sub 2@ [110]// alpha-Al@sub 2@O@sub 3@ [-2110]. Total conductivity measurements clearly show that the conductivity in these films is significantly higher than that in the polycrystalline material with the maximum values for the samarium concentration of 11 cation %. We will discuss these results along with the effects associated with grain boundaries in conductivity in these films.