Structural, Optical and Multiferroic Properties of BiFeO3 Nanoparticles Synthesized by Soft Chemical Route

BiFeO3 nanoparticles were prepared via a soft chemical method using citric acid and tartaric acid routes followed by calcination at low temperature. Structural characterization showed remarkably different conditions for pure phase formation from both routes. The tartaric acid route was effective in obtaining pure phase BiFeO3 nanoparticles while citric acid route required leaching in dilute nitric acid to remove impurity phases. Further optical, magnetic, and dielectric characterizations of pure phase BiFeO3 nanoparticles obtained by tartaric acid route were done. X-ray diffraction and Raman spectroscopy confirmed the distorted rhombohedral structure of BiFeO3 nanoparticles. The average crystallite size of BiFeO3 nanoparticles was found to vary in the range 30–50 nm. Fourier Transformed Infrared spectra of BiFeO3 samples calcined at different temperatures were studied in order to analyze various bond formations in the samples. UV-Visible diffuse absorption showed that BFO nanoparticles strongly absorb visible light in the wavelength region of 400–580 nm with absorption cut-off wavelength of 571 nm. The band gap of BiFeO3 nanoparticles was found to be 2.17 eV as calculated from absorption coefficient spectra. Magnetic measurement showed saturated hysteresis loop indicating ferromagnetic behavior of BiFeO3 nanoparticles at room temperature. Temperature dependent dielectric constant showed anomaly well below the antiferromagnetic Néel temperature indicating decrease in antiferromagnetic Néel temperature of BiFeO3 nanoparticles.