Cation Size Mismatch and Charge Interactions Drive Dopant Segregation at the Surfaces of Manganite Perovskites

Cation segregation on perovskite oxide surfaces affects vastly the oxygen reduction activity and stability of solid oxide fuel cell (SOFC) cathodes. A unified theory that explains the physical origins of this phenomenon is therefore needed for designing cathode materials with optimal surface chemistry. We quantitatively assessed the elastic and electrostatic interactions of the dopant with the surrounding lattice as the key driving forces for segregation on model perovskite compounds, LnMnO3 (host cation Ln = La, Sm). Our approach combines surface chemical analysis with X-ray photoelectron and Auger electron spectroscopy on model dense thin films and computational analysis with density functional theory (DFT)…