Solid-state synthesis of La_0.75Gd_0.25FeO₃ nanoparticles for the enhanced photodegradation of methylene blue under sunlight irradiation

The perovskite powder La_0.75Gd_0.25FeO₃, abbreviated as LGFO, has been successfully synthesized via a solid–solid process and thoroughly investigated using various laboratory techniques. X-ray diffraction (XRD) analysis revealed that the studied powder exhibits an orthorhombic crystal system with the space group Pbnm, accompanied by the formation of nanometric crystallites measuring approximately 41 nm at a synthesis temperature of 1200 °C. The scanning electron microscope (SEM) image exhibits a uniform distribution of grains across the sample surface. Notably, the band gap value of LGFO was estimated using Tauc plot to be 2.40 eV, this value is lower than that of the pure LaFeO₃ phase, and discrepancy attributed to variations in crystallite size and the presence of substituted dopant ions. In a photocatalytic evaluation, LGFO demonstrated remarkable activity in degrading methylene blue (MB) under sunlight irradiation, surpassing the performance of pure LaFeO₃. The decomposition yield reached up to 61% after 120 min of solar exposure, exhibiting a first-order reaction kinetics behavior with an estimated rate constant of 0.00838 min⁻¹.