Structural and Optical Characterization of Multiferroic BiFeO3 Nanoparticles Synthesized at Different Annealing Temperatures

Multiferroic BiFeO3 (BFO) synthesis without any secondary phase is a big challenge. In this work, BFO nanoparticles were prepared using the sol-gel method at three different annealing temperatures. In order to observe the structure of prepared nanoparticles, X-ray diffraction (XRD) was used. The lucid crystalline structure of pure BFO nanoparticles was confirmed by the XRD pattern. In XRD pattern of these BFO nanoparticles, a secondary phase (Bi2Fe4O9) was observed. A phase shift was noticed with increasing annealing temperature. To scrutinize the grain morphology of synthesized nanoparticles, field emission scanning electron microscopy (FESEM) was performed. Energy dispersive X-ray spectroscopy (EDS) analysis had also been done for three different annealing temperatures. With increasing annealing temperature from 500 to 700 °C, particle size increased from 151 nm to 318 nm and crystallite size increased from 30.6 nm to 54.3 nm. In order to measure diffuse reflectance, a UV/Vis/NIR spectrophotometer was used and then optical band gap (Eg) was determined. Band gap energy increased from 1.96 eV to 2.04 eV for the increment of annealing temperature from 500 to 700 °C. The annealing temperature of 500 °C was found to be the optimal condition for synthesizing BiFeO3 nanoparticles.