Gd 3+ -substituted BiFeO 3 perovskite nanoparticles: facile synthesis, characterization, and applications in heterogeneous catalysis.

We present the combustion-based synthesis of BiFeO 3 (BFO) and Gd:BiFeO 3 perovskite nanoparticles. XRD analysis demonstrates that the undoped BFO ( x = 0) perovskite sample shows a single perovskite phase with a rhombohedral structure. However, increase in the Gd 3+ content from x = 0.05 and 0.15 to 0.25 led to the occurrence of a structural phase transformation from rhombohedral (BiFeO 3 ) to orthorhombic (Bi 2 Fe 4 O 9 ). With an increase in the Gd-dopant the average crystallite size of rhombohedral structures increased from 16 to 23 nm. The perovskite samples were examined using XPS, which confirmed the presence of Bi 3+ , Gd 3+ , Fe 2+ , and O 2+ ions. FT-IR spectroscopy indicated the existence of elemental functional groups in the synthesized perovskite nanoparticles. Furthermore, the direct band gap measured by DRS reduced from 2.16 to 2.0 eV as the Gd concentration increased. The nanoparticles of the BFO perovskite had an uneven shape, a tendency to agglomerate, and fused grains with defined grain boundaries. At ambient temperature, both the undoped and Gd:BFO perovskite nanoparticles exhibit a ferromagnetic characteristic. It was found that the BET surface area of the undoped and Gd-doped BFO perovskite nanoparticles varied progressively from 4.38 to 33.52 m 2 g -1 . The catalytic oxidation studies conducted in a batch reactor under air conditions revealed that the synthesized catalysts, in particular, Gd:BFO ( x = 0.25), exhibited higher conversion and selectivity efficiencies for glycerol (con. 100% and sel. 99.5%, respectively).