Crystal Structure and Photocatalytic Properties of Bismuth-Doped Lanthanum Ferrite

In this work, the photocatalytic activity of bismuth-doped lanthanum ferrite, La1-xBixFeO3 (0 = x = 0.5), synthesized by high-energy ball milling assisted by annealing, is reported. X-ray diffraction and Rietveld refinement confirmed that pure lanthanum ferrite with an orthorhombic structure (Pbnm) was obtained for dopant levels lower than 0.2 mol Bi3+. Higher dopant levels produce the transformation from LaFeO3 to BiFeO3 with the same orthorhombic structure (Pnma), and consequently, a mixture of phases is present in these compositions. The band gap values obtained from diffuse reflectance spectroscopy show a general decrease as bismuth content increases, from 2.10 eV for undoped to 2.00 eV for 0.5 mol doped. For any increase in Bi3+ concentration, all values indicate visible-light absorption. LaFeO3 synthesized powders show high photocatalytic degradation of methylene blue under visible light. Nevertheless, the synthesized bismuth-doped ferrites show a slight decrease, attributed to (i) the modification in the band gap, (ii) the change in the band gap border, and (iii) the presence of a mixture of phases, inducing a heterojunction effect.