Bulk Perovskite Oxides: Synthesis, Structure–Property Relationships and Engineering Applications

Perovskite oxides have emerged as a versatile class of functional materials owing to their structural flexibility, tunable defect chemistry, mixed ionic–electronic conductivity, and excellent thermal stability. These characteristics make them attractive for engineering applications in heterogeneous catalysis, solid oxide fuel cells (SOFCs), oxygen separation membranes, and sustainable energy conversion. This review critically analyzes recent advances in the crystal structure, physicochemical properties, defect chemistry, synthesis strategies, and engineering applications of bulk perovskite oxides and related Ruddlesden–Popper phases. Conventional and advanced synthesis methods, including solid-state, sol–gel, Pechini, hydrothermal, solution combustion, and spray pyrolysis approaches, are compared with respect to compositional homogeneity, microstructure, oxygen vacancy formation, scalability, and functional performance. The review demonstrates that the performance of perovskite materials is governed by the interplay between crystal structure, defect chemistry, synthesis route, and oxygen mobility. Recent developments in methane reforming, catalytic oxidation, SOFC electrodes, oxygen separation membranes, and perovskite–fluorite nanocomposites highlight the broad engineering potential of these materials. Despite significant progress, challenges remain in achieving long-term structural stability, reproducible large-scale synthesis, and precise defect engineering. Future research should focus on sustainable manufacturing strategies, nanocomposite design, and data-driven materials optimization to accelerate the development of next-generation functional perovskite materials.