Influence of Sr Substitution on the Phase Formation and Electrochemical Properties of La1-xSrxMnO3-δ Perovskites

Abstract

La1-xSrxMnO3-δ (x = 0, 0.15, 0.30 and 0.50) perovskite powders were synthesized by a modified Pechini sol-gel method. Differential thermal analysis revealed that heat treatment at approximately 800 °C is required for complete formation of the perovskite phase. X-ray diffraction analysis showed that the as-synthesized powders possess an orthorhombic perovskite-related structure (Pnma), while heat treatment at 800 °C results in the formation of a single-phase rhombohedral perovskite structure (R-3c). Scanning electron microscopy demonstrated that the powders consist of agglomerated nanoparticles with grain sizes ranging from 50 to 200 nm. Electrochemical investigations revealed that Sr substitution significantly influences the capacitive properties of La1-xSrxMnO3-δ. The highest specific capacitance of 118 F g⁻¹ was obtained for La0.7Sr0.3MnO3-δ, which is attributed to an optimal balance between electronic conductivity and the concentration of electrochemically active Mn³⁺/Mn⁴⁺ redox centers. The results demonstrate that controlled Sr substitution is an effective approach for tailoring the structural and electrochemical properties of La1-xSrxMnO3-δ, making these materials promising candidates for supercapacitor electrode applications.