THERMAL PROPERTIES, COMPATIBILITY OF Pr1-хSrхFe1-yCoyO3-δ PEROVSKITES WITH ELECTROLYTE MATERIALS FOR REVERSIBLE FUEL CELLS

The search for thermally stable and chemically compatible cathode materials remains a crucial task in advancing reversible solid oxide fuel cells (RTFCs) for high-temperature hydrogen electrolysis. Among various candidates, rare-earth ferrite–cobaltites of the general formula Pr1-хSrхFe1-γCoγO3-δ (0 ≤ x ≤ 0,4; y = 0,2; 0,5) have attracted considerable attention due to their distorted perovskite structure with orthorhombic GdFeO3-type symmetry (Pbnm), high mixed ionic–electronic conductivity, and favorable thermomechanical compatibility with electrolyte materials. In this study, a series of Pr–Sr–Fe–Co perovskites was synthesized via a self-propagating high-temperature synthesis (SHS) route, ensuring high crystallinity and phase purity. Structural characterization by X-ray diffraction confirmed the formation of single-phase orthorhombic perovskites, with systematic lattice parameter variations depending on Sr and Co substitution. The tolerance factor calculations and diffraction analyses indicated robust structural stability across all studied compositions. Thermal expansion coefficients (CTE) α were measured over 300–1200 °C, revealing acceptable compatibility with solid oxide electrolytes up to ~800 °C, though Sr- and Co-rich compositions exhibited pronounced chemical expansion at higher temperatures. Chemical compatibility tests with YSZ and GDC electrolytes demonstrated that Sr-containing perovskites partially reacted with YSZ, leading to the formation of secondary phases (e.g., SrZrO3, PrZr2O7), while all compositions remained stable in contact with GDC even after sintering at 1200 °C. This highlights GDC as the more suitable electrolyte counterpart for these cathode materials. The obtained results provide insights into the correlation between cation substitution, structural parameters, thermal expansion behavior, and phase stability. Overall, Pr1-хSrхFe1-γCoγO3-δ perovskites emerge as promising cathode materials for RTFCs applications, particularly in systems employing GDC electrolytes. These findings contribute to the optimization of composition and operating conditions for durable, high-efficiency hydrogen energy systems. Keywords: reversible fuel cells, perovskite oxides, Pr–Sr–Fe–Co ferrite–cobaltites, thermal expansion, electrolyte compatibility.