Optical properties of BiFe_0.95Mn_0.05O₃nanoparticles & BiFe_0.95Mn_0.05O₃@SiO₂nanocomposite

Transition metal ion (Mn2+) doped BiFeO3 (BiFe0.95Mn0.05O3) nanoparticles were synthesized by low temperature polymer assisted hydrothermal method. The core/shell BiFe0.95Mn0.05O3@SiO2 nanocomposite was prepared using Stöber method. X-ray diffraction patterns with rietveld analysis confirm a FeO6 octahedron distorted rhombohedral structure. The formation of amorphous silica shell was ensured through the observance of a broad hump in the XRD pattern, FESEM and HRTEM microstructures and UV-Vis studies. The particles with an average size of 127 nm were found to be agglomerated and covered with a silica layer of approximately 10-12 nm. The energy band gaps (Eg) were determined from the diffused reflectance spectra by using Tauc's relation. It was observed that the Mn2+ doping decreased the Eg values to 1.75 eV as compared to that of 2.01 eV for pristine BFO. The optical spectrum of the nanocomposite exhibited two bandgaps, i.e 2.31 eV for BFMO and 5.1 eV for SiO2 shell. The observed 6A1g ? 4T2g transition at 1.88 eV and p-d CT transitions at 3.27 eV are found to be red-shifted in comparison to pristine BFO and may be attributed to the slight disturbance in FeO6 octahedra because of Mn2+ substitution.