Structural and optical studies of BiFeO3@SiO2 core/shell nanoparticles

Sol-gel synthesized bismuth ferrite (BiFeO3) nanoparticles (NPs) were encapsulated with SiO2 by the Stober method. The structural and microstructural studies were carried out by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), high resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM). The XRD pattern revealed the coating of SiO2 on distorted rhombohedral (R3c) structured BiFeO3 (BFO). The particle size of BFO was estimated to be 100-120 nm. The inter-planar spacing between the (1 1 0) planes was found to be 0.28 nm. The coating of amorphous SiO2 shell on crystalline BFO was quite evident from the TEM micrographs. The presence of O-Si-O stretching vibration in FTIR spectra reconfirmed the coating of SiO2. The direct bandgap energy was calculated to be 2.02 eV for BFO and 2.12 eV for BFO@SiO2 (from UV-vis spectra). The optical absorption was observed to be higher for BFO@SiO2 than BFO. These NPs may be used as photoelectrodes in dye sensitized solar cell application.