High-performance atmospheric plasma sprayed La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ enabled by in-situ metal oxidation: Progress in SOFC cathode design

La_0.6Sr_0.4Co_0.2Fe_0.8O_3–δ (LSCF) cathodes fabricated via atmospheric plasma spraying (APS) have emerged as a compelling alternative to conventional sintering techniques, primarily by mitigating detrimental interfacial reactions with ZrO₂-based electrolytes. However, the performance of APS-LSCF cathodes is often constrained by intrinsic porosity and the B-site elements evaporation inside plasma jet, leading to reduced reactivity compared to their sintered counterparts. Although the use of volatile pore-forming agents is known to improve gas pathways, deposition efficiency and mechanical strength are often reduced, leading to increased processing costs. In this study, a novel strategy is developed by incorporating a controlled volume fraction of Fe metal powder into the feedstock to form a composite LSCF–Fe cathode. During heat treatment, the dispersed Fe particles undergo in-situ oxidation and volumetric expansion, promoting microcrack propagation and improving gas diffusion while having minimal impact on mechanical strength and deposition efficiency. Simultaneously, Fe elements diffuses into the LSCF lattice partially compensated for B-site deficiencies induced by plasma-induced evaporation, contributing to the restoration of the perovskite structure. Characterization of oxygen vacancy content and electrochemical measurements confirmed the dual-functional mechanism of the introduced Fe particles, resulting in enhanced cathode reactivity. A polarization resistance (R_p) as low as 0.072 Ω cm² at 750 °C was achieved in symmetric cells, while single-cell testing revealed a 52 % increase in peak power density compared with a pure LSCF cell. Moreover, structural and electrochemical stability was maintained over 250 h test. These findings highlight a cost-effective and scalable route for optimizing APS-LSCF cathodes and accelerating the commercialization of high-performance solid oxide fuel cell (SOFC) technologies.