Influence of Sr Concentration and A‐Site Deficiency on the (La ₁₋ <i> _y </i> Sr <i> _y </i> ) <i> _x </i> Cr _0.5 Mn _0.45 Ni _0.05 O ₃₋ <i> _δ </i> Solid Ox

ABSTRACT In this study, the La/Sr ratio and A‐site deficiency of (La 1− y Sr y ) x Cr 0.5 Mn 0.45 Ni 0.05 O 3− δ (LSCMN) were systematically varied to investigate the effect of these modifications on lattice parameters, surface composition, and initial electrochemical performance. Studied materials were thermally treated in oxidizing and reducing gas environments and thereafter analyzed using X‐ray diffraction (XRD), time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS), and electrochemical analysis methods. X‐ray analysis of samples heat‐treated in air revealed that the La/Sr ratio influences the Mn 3+ /Mn 4+ ratio in LSCMN material, but the influence of A‐site deficiency is minor. After thermal treatment in a highly reducing environment, expansion of lattice parameters was observed, caused by the reduction of Ni 2+ to Ni 0 and partial reduction of Mn 4+ to Mn 3+ and simultaneous formation of oxide ion vacancies. The highest lattice changes were observed in the highest Sr concentration and at the 1%–3% A‐site deficiency range. The highest electrochemical activity was observed when the Sr content remained low ( y = 0.2). The most stable systems had low A‐site deficiency. The study reveals that chemical and structural characteristics of the electrode surface, particularly the segregation of LSCMN components, play an essential role in the electrochemical performance and stability.