1607
Surface Composition of Layered Ruddlesden-Popper Lan+1NinO3n+1 (n = 1, 2 and 3) Epitaxial Films

Monday, 25 May 2015: 11:00
Boulevard Room C (Hilton Chicago)
K. T. Wu (Department of Applied Chemistry, Kyushu University, Department of Materials, Imperial College London), H. TÚllez, J. Druce (wpi-I2CNER, Kyushu University), M. Burriel (LMGP, France, Department of Materials, Imperial College London), T. Ishihara (wpi-I2CNER, Kyushu University, Department of Applied Chemistry, Kyushu University), J. A. Kilner (Imperial College London, wpi-I2CNER, Kyushu University), and S. J. Skinner (Imperial College London, London, UK)
Layered Ruddlesden-Popper (RP) type oxides, formulated Lan+1NinO3n+1(n = 1, 2 and 3), have recently been suggested as candidates for intermediate temperature solid oxide fuel cell (IT-SOFC) cathodes. Compared to traditional cathodes (e.g. LSM), these mixed ionic-electronic conductors (MIECs) possess highly promising oxygen surface exchange kinetics, which is not limited to the triple phase boundary (TPB), but the entire surface exposed to the gas phase.

The oxygen surface exchange activity is strongly influenced by the surface composition and atomic surface structure where the adsorption and dissociation of molecular oxygen take place. These effects may influence the rate determining step [1], and consequently the ultimate efficiency of the SOFC device. More importantly, compared to bulk samples, the oxygen transport kinetics for thin-film samples is significantly dominated by the surface process [2]. A series of Lan+1NinO3n+1(n = 1, 2 and 3) epitaxial films have been deposited using pulsed laser deposition (PLD) technique for the fundamentally surface analysis [3]. It is therefore of great importance to understand the surface and near-surface chemical compositions and the structure (or termination) of the obtained films. These investigations will aid in the understanding of the electrochemical properties of lanthanum nickelate cathode materials in surface regions [4].

In this work, the kinetic nature of Lan+1NinO3n+1(n = 1, 2 and 3) epitaxial films deposited by PLD was systematically investigated using high-sensitivity low-energy ion scattering (HS-LEIS). The compositional analysis for the outermost and near-surface of these obtained films was also studied. The results reveal that the phenomena of surface reconstruction may decrease the active surface area during the deposition and post-treatment process of the thin-film materials.

References

[1]        S. B. Adler, Chem. Rev. 2004, 104, 4791.

[2]        G. Kim, S. Wang, A. J. Jacobson, C. L. Chen, Solid State Ionics 2006, 177, 1461.

[3]        K.-T. Wu, Y.-A. Soh, S. J. Skinner, Mater. Res. Bull. 2013, 48, 3783.

[4]        J. Kilner, S. Skinner, H. Brongersma, J. Solid State Electr. 2011, 15, 861.