Effect of Atmospheric Carbon Dioxide and Strontium Content on Surface Segregation in Strontium Doped Lanthanum Cobalt Iron Oxide Thin Films

Abstract

This study investigates surface segregation behavior and phase formation in LaxSr1-xCo0.2Fe0.8O3-δ (LSCF), a commonly used cathode material for solid oxide fuel cells (SOFCs). (100)-oriented LSCF thin films with varying ‘x’ values were deposited on (110)-oriented NdGaO3 (NGO) substrates by pulsed laser deposition (PLD). Compositional changes on the surface of LSCF thin films were measured using total reflection x-ray fluorescence (TXRF) technique in real time at 800°C under different CO2 partial pressures. Ex-situ electronic structure measurements were carried on the post-annealed samples using hard x-ray photoelectron spectroscopy (HAXPES). The thin-films were also characterized in cross-section by high-resolution transmission electron microscopy (HRTEM), and composition profiles in the LSCF matrix adjacent to the surface segregated phases were analyzed using energy-dispersed x-ray spectroscopy (EDS). The thermodynamics and kinetics of the segregation and phase formation phenomena as a function of atmospheric CO2 partial pressure and Sr content is discussed in this presentation.