La1xSrxCo1yFeyO3

La1−xSr x Co1−y Fe y O3 (often written La1−xSrxCo1−yFeyO3−δ) is a family of mixed-oxide perovskites in which a portion x of lanthanum on the A-site is replaced by strontium and a portion y of cobalt on the B-site is replaced by iron. This double substitution creates a perovskite ABO3 lattice whose overall charge balance is maintained by mixed valence states of cobalt and iron and by oxygen vacancies (δ) that develop with temperature and oxygen partial pressure. The variables x and y (0 ≤ x, y ≤ 1) control electronic structure, oxygen nonstoichiometry, and functional properties.

The structure remains perovskite-like, with distortions that depend on composition and temperature, ranging from orthorhombic to rhombohedral or near-cubic symmetry in some regimes. Sr2+ substitution introduces hole doping, typically increasing electronic conductivity and modulating catalytic activity. The Fe substitution on the B-site further tunes redox chemistry, ionic mobility, and stability. Oxygen nonstoichiometry δ is a common feature, affecting both conductivity and catalytic behavior.

Key properties include mixed ionic-electronic conductivity, tunable catalytic activity for oxygen reduction and oxidation reactions, and magnetic behavior that varies with Co/Fe ratios. These materials are studied for their ability to function as cathodes in intermediate-temperature solid oxide fuel cells (IT-SOFCs) and as electrocatalysts for various oxygen-based reactions. They may exhibit improved performance with Sr and Fe content but can face challenges such as Sr surface segregation, phase stability at high temperature, and compatibility with electrolytes.

Synthesis methods commonly include solid-state reaction, sol-gel processes, and deposition techniques for thin films, allowing control over phase purity, microstructure, and δ.