A Cation‐Specific Strain Design Principle for Surface Segregation in Perovskite Oxides

ABSTRACT

Surface segregation of A‐site cations is a major degradation pathway in conductive perovskite‐based (ABO ₃ ) oxygen electrodes used for fuel cells, water electrolysis, and CO ₂ reduction. Despite extensive studies, strain effects on A‐site segregation have not been systematically rationalized, particularly for La‐ and Sr‐based perovskites. In this study, computational calculations and experimental investigations were systematically conducted to elucidate how the intrinsic stability of A‐site cations governs their surface segregation behavior under lattice strain. As model systems, (Sr _x La _1‐x )MnO ₃ and Sr(Fe _x Zr _1‐x )O ₃ were investigated to represent La‐ and Sr‐based perovskite oxides, respectively. Notably, the two materials exhibit opposite strain‐dependent stabilization trends of A‐site cations. DFT calculations reveal that La and Sr cations are thermodynamically the most stable under compressive and tensile strains, respectively; applying strain in the direction that strengthens cation stability can effectively suppress cation segregation. These predictions are experimentally validated by surface compositional analyses of strain‐controlled epitaxial thin films. These findings provide a unified framework for understanding strain‐dependent A‐site segregation in perovskite oxides and offer a general design rule for enhancing the durability of perovskite‐based electrochemical electrodes.