Optimizing oxygen transport properties in Al-substituted La0.5Sr0.5Co0.8Fe0.2-xAlxO3-δ (x = 0–0.20) perovskites.

• La 1-x Sr x Co 1-y Fe y O 3 perovskite-type oxides are renowned for their remarkable mixed ionic-electronic conductivity. • We synthesized single-phase La 0.5 Sr 0.5 Co 0.8 Fe 0.2-x Al x O 3-δ (x = 0–0.20) perovskite oxides via solution combustion. • Introducing trivalent aluminum (Al3+) into perovskite B-site enhanced redox stability and mitigated oxygen variations. • Al-substitution significantly influenced surface morphology, oxygen nonstoichiometry, and electrical conductivity. • Oxygen nonstoichiometry significantly influenced oxygen transport parameters, resulting in improved D chem and K chem at 900 °C for these perovskites. In recent years, there has been a surge in the investigation of perovskite-type complex oxides, with a particular focus on La 1-x Sr x Co 1-y Fe y O 3 , renowned for their exceptional mixed ionic-electronic conducting (MIEC) properties. La 0.6 Sr 0.4 Co 1-y Fe y O 3 compositions have prominently emerged in this research domain. The hypothesis of enhancing redox stability and mitigating oxygen variations by incorporating trivalent aluminum (Al3+) into the B-site of perovskite structures has gained attention. In this study, single-phase La 0.5 Sr 0.5 Co 0.8 Fe 0.2-x Al x O 3-δ (x = 0–0.20) perovskite oxides were synthesized using the solution combustion technique. The physicochemical properties of the synthesized materials were thoroughly characterized, including their morphology, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) analysis, oxygen nonstoichiometry, and electrical transport properties. Results revealed lattice parameter variations associated with oxygen nonstoichiometry and B-site cation size, exhibiting a decline up to x = 0.10 followed by an increase. Al-substitution significantly influenced surface morphology, oxygen nonstoichiometry, and electrical conductivity. Notably, La 0.5 Sr 0.5 Co 0.8 Fe 0.1 Al 0.1 O 3-δ displayed lower electrical conductivity (676 S cm−1 at 300 °C) among the studied oxides. Oxygen nonstoichiometry had a significant impact on oxygen transport parameters, with these perovskites demonstrating improved chemical diffusion coefficient, D chem (5.5 × 10-5 cm2 s−1), and the oxygen surface exchange coefficient, K chem (2.32 × 10-5 cm s−1) at 900 °C, suggesting its potential as an oxygen transport membrane. These findings underscore the promising role of Al-substituted perovskite oxides in various advanced applications. [ABSTRACT FROM AUTHOR]