AVS 59th Annual International Symposium and Exhibition
    Oxide Heterostructures-Interface Form & Function Focus Topic Tuesday Sessions
       Session OX-TuP

Paper OX-TuP6
The Influence of Nano-Scale Interfaces and Co-Doping on the Oxygen Ionic Conductivity of Ceria and Zirconia Based Thin Film Electrolytes

Tuesday, October 30, 2012, 6:00 pm, Room Central Hall

Session: Oxide Interfaces and Heterostructures Poster Session
Presenter: M.I. Nandasiri, EMSL, Pacific Northwest National Laboratory
Authors: M.I. Nandasiri, EMSL, Pacific Northwest National Laboratory
Q. Langfitt, EMSL, Pacific Northwest National Laboratory
M. Quintero, EMSL, Pacific Northwest National Laboratory
T. Varga, EMSL, Pacific Northwest National Laboratory
A. Devaraj, EMSL, Pacific Northwest National Laboratory
S. Manandhar, EMSL, Pacific Northwest National Laboratory
P. Nachimuthu, EMSL, Pacific Northwest National Laboratory
V. Shutthanandan, EMSL, Pacific Northwest National Laboratory
S. Thevuthasan, EMSL, Pacific Northwest National Laboratory
A. Kayani, Western Michigan University
Correspondent: Click to Email
The high temperature operation of solid oxide fuel cells (SOFC) is one of the main challenges we have to overcome, especially for commercializing SOFC for portable power generating applications. Solid state electrolytes with enhanced oxygen ionic conductivity at low and intermediate temperatures are needed to lower the operating temperature of SOFC. Thus, there is an ongoing need to develop new electrolytes or modify existing electrolytes to enhance the ionic conductivity. Co-doping can be used to modify existing ceria and zirconia based electrolytes. On the other hand, new electrolytes can be developed by utilizing the engineered interfaces in multi-layer thin films. Here, we investigate the influence of nano-scale interfaces and co-doping on the ionic conductivity of ceria and zirconia based electrolytes.

In this study, we have grown (i) multilayers of high quality samaria doped ceria (SDC) and scandia stabilized zirconia (ScSZ) epitaxial thin films, and (ii) samaria and gadolinia co-doped high quality ceria thin films using oxygen plasma-assisted molecular beam epitaxy and characterized using various capabilities. The number of layers in the SDC/ScSZ multi-layer thin films was varied from 2 to 20 by keeping the total film thickness constant at 140 nm to understand the effect of nano-scale interfaces on the ionic conductivity. To understand the effect of co-doping on the ionic conductivity of optimized SDC thin films, Ce0.85Sm0.15-xGdxO2-δ (SGDC) thin films were deposited by varying the Gd concentration. The film growth was monitored using in-situ reflection high energy electron diffraction (RHEED). Structural properties of these films were studied using x-ray diffraction (XRD) and the XRD patterns confirmed the growth of epitaxial thin films. The film and layer thicknesses were determined by x-ray reflectivity. X-ray photoelectron spectroscopy was used to find the composition, depth profile and chemical state of elements of the films. The SDC/ScSZ multi-layer and SGDC thin films were carefully characterized using Rutherford backscattering spectrometry, coupled scanning transmission electron microscopy and atom probe tomography to study the oxygen vacancy and dopant distributions along with the inter-diffusion and dopant segregation at the interfaces. Oxygen ionic conductivity measurements were carried out as a function of temperature on well characterized samples using four probe surface impedance spectroscopy. Detailed analysis of oxygen ionic conductivity as a function of individual layer thickness, dopant concentration, and crystalline quality of the films will be discussed.