Rare-Earth Orthoferrites: Synthesis–Structure–Property Relationships, Functional Applications, and Future Perspectives

Rare-earth-based RFeO₃ orthoferrites are multifunctional materials distinguished by their structural flexibility, high chemical and thermal stability, and unique combination of magnetic, electrical, dielectric, optical, sensing, and catalytic properties. This review critically systematizes recent advances in the synthesis of RFeO₃ orthoferrites, the development of their structural and morphological characteristics, and the targeted control of their functional properties. The effects of solid-state reaction, optical floating-zone growth, sol–gel processing, sol–gel auto-combustion, coprecipitation, hydrothermal synthesis, and microwave-assisted synthesis on phase purity, crystallinity, particle size, morphology, and defect structure are compared. The influence of A- and B-site cation substitution, oxygen vacancies, FeO₆ octahedral tilting, and microstrain on charge transport, magnetic exchange interactions, and electronic structure is examined. The capabilities of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman and Fourier-transform infrared (FTIR) spectroscopy, electron microscopy, vibrating-sample magnetometry (VSM), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS) for elucidating structure–property relationships are assessed. The compiled evidence demonstrates that synthesis conditions and chemical modification produce interrelated changes in the phase composition, grain size, band-gap energy, dielectric and magnetic responses, and sensing and catalytic activity of orthoferrites. The application potential of RFeO₃-based materials in magnetic refrigeration, spintronics, supercapacitors, gas sensors, solid oxide fuel cells, magnetic memory, capacitors, photocatalysis, and electrocatalysis is evaluated. The analysis identifies the systematic elucidation of the “synthesis–structure–morphology–property–function” relationship, quantitative characterization of defect chemistry, standardization of measurement protocols, and evaluation of long-term operational stability as key priorities for future research.